GB2144348A - Crop grader - Google Patents

Abstract

Spacing between adjacent rollers 16 of a roller grader is adjusted by attaching the rollers to alternate pivots between consecutive links 19,21 of the driving chains and by controlling the path of the intervening pivots 22 so that they run in a path, during at least part of the sizing run, which is spaced in an adjustable manner from the path of the pivots to which the rollers are attached. As illustrated, this is achieved by provision of cam followers 37 on the intervening pivots, which cam followers 37 are directed by a cam 41 to a rail 23. The positions of the cam 41 and the rail 23 are adjustable. The path of the intermediate or secondary pivots 22 may be varied stepwise or gradually along the sizing run. <IMAGE>

Description

SPECIFICATION Improved crop grader This invention relates to crop graders, particularly for root crops such as potatoes, onions and carrots, and for fruits such as apples, tomatoes and cucumbers.

The grading of crops includes sizing, in which the crop is sorted into sizes in accordance with predetermined requirements, and also a visual inspection for rejection of damaged or sub-standard items and also of foreign matter, such as clods, stones or other inclusions.

The grading of vegetables including potatoes, onions, carrots, redbeet and many others requires that at some stage they be divided into different categories of size. The "size" of a potato, for example, can be measured in a number of different ways, by volume, by weight, or by a combination of its dimensions. The currently accepted definition of size is the dimension across the minimum size of a square hole through which the item will pass.

Thus a 40mm potato is one which will pass through a square hole 40mm x 40mm, but not a smaller one.

In practice this leads to difficulties because some varieties of potato, particularly the modern ones, are nowhere near spherical.

A potato which passes through a 40mm x 40mm square hole may have a minimum cross-section which is approximately elliptical in shape, about 45mm x 30mm, and a length perpendicular to this cross-section of anything up to 80mm.

As the sizes increase, the shape of the potatoes becomes more irregular. For this reason, the sizing achieved in graders which rely on the crop passing down through a square mesh is not particularly accurate, and a potato which could easily pass through the mesh may travel over or along it because it never orientates itself into the correct position.

The sizing is conventionally achieved in any of a number of ways, of which the most usual are the use of a shaking square mesh, a continuous screen grader, a spool grader or a roller grader.

In the shaking square mesh method, the crop is introduced on to a wire mesh (in some cases rubber or plastics-covered to reduce damage) whose size is such that the crop below a certain size will fall through the mesh and above that size will pass over it. The mesh is vibrated in such a way that it causes the crop to move about freely and rotate to some extent in order to find its smallest section and also to advance the crop over the screen at the same time. This system is particularly useful for spherical or near spherical objects. In some cases the different mesh sizes are placed one above the other and in others they are placed one following the other.

A continuous screen grader operates in the same manner as the shaking square mesh, in that the crop passes through square holes in a mesh, but the mesh is in the form of flexible chain or conveyor which is mechanically driven forward and shakes up and down at the same time. It is particularly suitable for near spherical objects, and has the advantage of being self-cleaning, because it returns upside down from the discharge point back to the beginning.

In a spool grader, a series of stationary shafts rotate with spools of such a shape that there exists between them a gap of the dimensions of the size of crop to be removed. The crop is rotated because it rests upon rotating spools and is moved over the machine either by declining the machine from shaft to shaft or because subsequent crop pushes it forward. This system is particularly suitable for spherical objects but is subject to a build up of mud on the spools. It is also damaging to early potatoes and onions which tend to get skinned by the rubbing action caused by the relatively high speed of rotation and the contact with surrounding crop.

In a roller grader, the crop is rotated and advanced on rollers which are set at such a distance apart that the crop passes through between the rollers. In one particular form, the rollers are mounted so as to be spced apart by a distance which varies as the rollers progress. However, the mechanical arrangements for achieving this are complex and expensive. They also require considerable routine maintenance. In addition, the mud which is a prevalent part of agriculture, particularly in the United Kingdom, may cause inaccurate grading.

All the above sizing systems suffer from the disadvantage that changing the required size is relatively complicated and expensive. In principle, one unit of sizer will only take out one size, and there is, therefore, a transfer from one unit to the next which usually involves a drop, which is damaging, or a transfer where the crop will remain stationary and rotate until pushed on by following crop, which tends to skin some crops.

According to the present invention there is provided a machine for sizing crops comprising a series of rollers extending laterally between endless chains consisting of links and pivots, and carrying the rollers on a closed path incorporating a sizing run and return run, means for rotating the rollers as they advance along the sizing run to rotate crops supported on the rollers that the crop having a dimension smaller than the spacing between rollers will fall between adjacent rollers, and means for controlling the spacing between adjacent rollers on the sizing run, in which the rollers are connected to primary pivots in the chain and in between each primary pivot there is at least one secondary pivot, and in which the sizing run includes means for maintaining the path of the secondary pivots at a predetermined spacing from the path of the primary pivots whereby the longitudinal spacing between adjacent rollers is controlled.

If the path of the secondary pivots is maintained at a constant distance from the path of the primary pivots, then the spacing between the rollers remains constant, but in a normal sizing machine it would be reduced either stepwise or gradually so that the spacing between the rollers increased in a similar manner during the progress along the siz ing run.

In particular, the machine preferably comprises means for diverting the secondary pivots to a path at maximum spacing from the path of the primary pivots prior to the beginning of the sizing run. The diverting means may comprise a cam engaging cam followers coaxial with the secondary pivots and laterally offset therefrom. Alternatively and preferably, the diverting means comprises a cam engaging cam followers mounted on links pivotal about the primary pivots and solid with only one of the links of the chain connected by the respective pivots, conveniently the trailing links.

A sprocket is conveniently provided for each chain at each end of the sizing run. Either or both of the sprockets may be powered to enable the proper tensioning of the chain over the sizing run so as to allow the spacing to be controlled. It is also preferred that the return run of each chain, and the rollers, be allowed to hang freely, in substantially catenary form, to allow for variations in the configuration of the sizing run.

It is normal for the rollers in a roller grader or sizing machine to be driven by being in engagement with a static rail having friction surface, but in a normal machine, the weight of the roller determines the reaction between the friction surface and the roller, therefore, the maximum rotational force that can be provided. With the arrangement according to the invention, if the secondary pivots are spaced below the static rail, there is in fact a downward component of tension in the links which enhances the downward force on the static rail, and thereby increases the driving force.

It is the preferred arrangement that the primary pivots constitute alternate pivots in each chain, and that, therefore, there should only be one secondary pivot between each pair of primary pivots.

The invention will be more particularly described with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a side view of a sizing machine in accordance with a preferred embodiment of the invention; Figure 2 is a view to an enlarged scale showing the initial part of the sizing run; Figure 3 is a partial section taken through one of the transverse rollers of figure 2; Figure 4 is a view similar to figure 2 and showing an alternative; and Figure 5 is a partial section taken through one of the transverse rollers of figure 4.

Turning first to figure 1, there is shown a roller grader or sizing machine which is mounted on a frame 11, having caster wheels 12 to enable the machine to be manhandled or pushed over a hard surface, such as a concrete floor, to a desired location.

The wheels 12 may be omitted if the machine is to form part of a fixed grading line. The machine will normally have its own electric motor as a power source, but it could be driven by a tractor power-take-off. Transversely mounted in the frame as shown are three belt conveyors 13, 14 and 15 for taking off respectively, small, medium and large crop. As an example, the sizing for the conveyor 13 will be 40mm, that for the conveyor 14 will be 60mm and that for the conveyor 15 will be lOOmm. Such a maximum sizing is larger than the smallest diameter of any normally grown potato or onion, so normally no crop would pass over the end.The grading is done by a series of rollers 16 which extend the width of the machine between two chains which drive the rollers 16 along a generally horizontal path in a sizing run above the conveyors 13, 14 and 15, and back along an unsupported generally catenary-form return run extending beneath these conveyors. Prior to the beginning of the sizing run of each chain there is located a first sprocket 17, and beyond it there is located a second sprocket 18. Either or both of these sprockets 17 and 18 may be driven.

The rollers 16 are attached to alternate pivots (primary pivots 16a) between consecutive links 19 and 21 of the chain, and by constraining the intervening or secondary pivots 22 to follow a path different from that of the primary pivots 16a, the spacing between adjacent rollers 16 may be controlled. It will be sesn from inspection of Figure 1 that the secondary pivots 22 follow a path controlled by a first rail 23 when above the conveyor 13. A second rail 23a provides a substantially stepwise change in the position of the path of the pivots 22 at the line 24 marking the changeover between the conveyor 13 and the conveyor 14. At this point, the path of the pivots 22 becomes considerably closer to the path of the primary pivots 16a, which are substantially coincident with the axes of the rollers 16, so the rollers 16 move out to a wider spacing.On reaching the point marked by the line 25, between the conveyors 14 and 15, the rail 23a terminates so that the secondary pivots are no longer constrained to follow a separate path and are pulled by the tension of the chain into substantially the same path as the primary pivots 16a.

The adjacent rollers 16 are then pulled by the chain tension to their maximum spacing of two pitches of the chain (e.g.152mm) between their axes, giving a maximum gap between adjacent rollers 16, which in the example given is lOOmm.

It will be understood that the examples given are purely illustrative and that either more or less than three different transverse take-off conveyors may be used, with a corresponding number of grading zones. Also, the paths of the primary and secondary pivots may be brought together in a gradual manner rather than stepwise.

Also by way of example, the width of the machine, i.e. the effective length of the rollers 16 between the primary pivots 16a may be between 600mm and 1800mm.

Figure 2 and 3 show how the rollers 16 may be mounted by means of bearings 31 on shafts 32 which are attached to pivots 33 supporting the links of the chain. These figures also show how the rollers 16 are rotated during their movement along the sizing run by frictional contact with a friction facing 34 on a static rail 36. Figure 3 also shows how the secondary pivots 22 have cam followers 37 in the form of roller or preferably ball bearings coaxial with the pivots 22 and laterally offset therefrom. All the pivots carry intermediate rollers 38 and 39 between the links for engagement by the sprockets 17 and 18. The rollers 16 are raised on the sprockets 17 to the level of the sizing run and directed onto the rail 36 by suitable guides. The rollers then commence to rotate.The cam followers 37 on the secondary or intervening pivots engage on a cam 41 which thus moves the secondary pivots onto a path spaced from the primary pivots 16a, and leading to the rail 23 so that the chain is in the form of a series of V's, thus bringing the rollers 16 closer together. The cam 41 is shaped to ensure that the force along each link is never perpendicular to the cam face but always maintains a component of force along the cam face causing the cam follower to continue to advance. The cam 41 may for instance be such as to pull adjacent rollers 16 to a spacing of 25mm, but this spacing may be varied by adjustment of the position of cam 41 or of its form.

As illustrated in Figure 2, an adjustment slot 42 is provided in 8 which the trailing edge of the cam may be moved up and down as required. On leaving the cam 41, the cam followers 37 engage the underside of the rail 23 which either maintains the postion of the cam followere 37 to keep a horizontal path for the pivot 22, or allows them to rise gradually. As has previously been described, a second rail 23a at a somewhat higher level may be provided to give an abrupt change in the path, and thus in the spacing of the rollers 16.

The rail 23 is shown as being attached to a portion 44 of the frame of the machine by means of a securing bolt 45 co-operating with a slot 46 so that the height of the rail 23 may be varied to give proper control of the required path. The adjustment may be achieved by means of an adjusting screw 47.

It will be seen that by putting the links 19, 21 into V form, there is a substantial downward component of force in the tension in the links and this tends to pull the rollers 16 down on to the friction face 34, thereby making the drive more positive than in a conventional arrangement in which the weight of the rollers, and the crop on them, controls the maximum amount of friction drive which may be imparted.

It will be appreciated that the operator is provided with a considerable choice of sizing profile by varying the positions of the cam 41 and the rails 23 and 23a, and this to some extent affects the length of chain between the sprockets 17 and 18 on the sizing run. To compensate for this variation, and to provide a constant tension, which is important for smooth running and accurate roller spacing of the machine, the entire return run of the chains is normally left unsupported, so that it hangs in a natural catenary.

In the alternative illustrated in figures 4 and 5, the cam followers 37 are replaced by cam followers 51 mounted on small brackets 52 or links pivotable about the primary pivots 16a and solid with the trailing one 19 only of the links 19 and 21 connected at that pivot 16a. The cam followers 51 or rollers engage, as the primary pivots 16a leave the sprocket 17, under a cam surface 53 and are constrained to turn counter-clockwise as viewed in figure 4, as the rollers 16 advance. this movement entrains the links 19, so that the links 19 and 21 form the series of narrow Vs required for close spacing of the rollers 16.

The cam followers 51 advance beneath a rail 54, serving to maintain the height of the cam followers 51 in similar manner to the rail 23 previously described. The rail 54 may be inclined or level, and it may be followed by a further rail at a greater height analogous to the rail 23a. The compression in the links or brackets 52 has a downwards component of force tending to enhance the frictional grip between the rollers 16 and the rail 36, or the friction lining 34 covering it.

Various other modifications have been made within the scope of the invention.

Claims (13)

1. A machine for sizing crops comprising a series of rollers extending laterally between endless chains consisting of links and pivots, and carrying the rollers on a closed path incorporating a sizing run and a return run, means for rotating the rollers as they advance along the sizing run to rotate crops supported on the rollers so that the crop having a dimension smaller than the spacing between the rollers will fall between adjacent rollers, and means for controlling the spacing between adjacent rollers on the sizing run, in which the rollers are connected to primary pivots in the chain and in between each primary pivot there is at least one secondary pivot, and in which the sizing run includes means for maintaining the path of the secondary pivots at a predetermined spacing from the path of the primary pivots, whereby the longitudinal spacing between adjacent rollers is controlled.

2. A machine as claimed in claim 1, comprising means for diverting the secondary pivots to a path at maximum spacing from the path of the primary pivots prior to the beginning of the sizing run.

3. A machine as claimed in claim 2, in which the diverting means comprises a cam engaging cam followers coaxial with the secondary pivots and laterally offset therefrom.

4. A machine as claimed in claim 2, in which the diverting means comprises a cam engaging cam followers mounted on links pivotal about the primary pivots and solid with only one of the links of the chain connected by the respective pivots.

5. A machine as claimed in claim 4, in which the links carrying the cam followers are solid with the trailing links on the pivots.

6. A machine as claimed in any of claims 2 to 5, comprising at least one substantially stepwise reduction in the spacing of the paths whereby the spacing between adjacent rollers is increased partway along the sizing run.

7. A machine as claimed in any of claims 2 to 5, in which the spacing between the paths is gradually reduced over at least part of the length of sizing run, whereby the spacing between the rollers is gradually increased.

8. A machine as claimed in any of the preceding claims, in which the return run of the chains is unsupported and allowed to hang freely.

9. A machine as claimed in any of the preceding claims, comprising a sprocket for each chain at each end of the sizing run, and in which either or both of the sprockets is powered.

10. A machine as claimed in any of the preceding claims, in which the rollers are driven in rotation by being partly in contact with a friction surface on a static rail extending along the sizing run.

11. A machine as claimed in claim 10, in which the tension of the links pulls the rollers positively towards the static rail.

12. A machine as claimed in any of the preceding claims, in which the primary pivots constitute alternate pivots in the chains.

13. A machine for sizing crops substantially as hereinbefore described with reference to the accompanying drawings.