WO2004110130A1

WO2004110130A1 - Fruit harvester

Info

Publication number: WO2004110130A1
Application number: PCT/AU2004/000793
Authority: WO
Inventors: Nicholas Albert William Fielder
Original assignee: Aoh Limited
Priority date: 2003-06-17
Filing date: 2004-06-17
Publication date: 2004-12-23

Abstract

A harvester for harvesting tree borne fruits comprising a base (11) supported or adapted to be supported from a vehicle, a trunk gripping member (15, 17, 19) supported from the base (11), the gripping member (15, 17, 19) being adapted to at least partially encircle the trunk and having an axial extent, the gripping member (15, 17, 19) provided with a gripping element (15, 17) which is capable of being activated to grippingly engage the trunk of a tree at two vertically spaced locations to hold the trunk substantially stationary relative to the gripping member (15, 17, 19) at the locations, the gripping element (15, 17) engaging a substantial portion of the perimeter of the trunk adjacent the gripping element (15, 17), a vibratory means (31, 49, 51) associated with the upper end of the gripping member (15, 17, 19) to induce a cyclic lateral movement of the upper portion of the gripping member (15, 17, 19) and the upper portion of the trunk engaged by the gripping element (15, 17) relative to the lower portion of the gripping member (15, 17) and the lower portion of the trunk.

Description

"Fruit Harvester"

Field of the Invention

This invention relates to a harvester which is intended for harvesting tree borne fruits.

Throughout the following description and the claims which make up this specification the term "fruits" shall to be taken to include all forms of fruits, berries, nuts and the like. Furthermore, throughout the following description and the claims which make up this specification the term the "tree" shall be taken to include shrub, vine, tree, or the like.

In addition throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Background Art

In the harvesting of tree borne fruits such as olives, it is a known practice to provide a device to engage the trunk of the tree and then shake the tree in order to loosen the fruits from the tree and allow them to fall to the ground. Whilst this has proved to be quite successful in terms of harvesting of the fruit it has also been found, in some cases, to be quite damaging if not devastating to the tree being harvested. The damage that has been caused by previous harvesting equipment has comprised damage to the trunk or at least the cambium of the tree which is engaged by the harvester, which can either result in "ring barking" of the tree or damage which may affect future crops from the tree. Furthermore the shaking can cause significant disturbance of the roots of the tree which again can result in the death of the tree or a significant reduction in its fruit bearing characteristics. Disclosure of the Invention

Accordingly the invention resides in a harvester for harvesting tree borne fruits comprising a base supported or adapted to be supported from a vehicle, a trunk gripping member supported from the base, the gripping member being adapted to at least partially encircle the trunk and having an axial extent, the gripping member provided with a gripping element which is capable of being activated to grippingly engage the trunk of a tree at two vertically spaced locations to hold the trunk substantially stationary relative to the gripping member at the locations, the gripping element engaging a substantial portion of the perimeter of the trunk adjacent the gripping element, a vibratory means associated with the upper end of the gripping member to induce a cyclic lateral movement of the upper portion of the gripping member and the upper portion of the trunk engaged by the gripping element relative to the lower portion of the gripping member and the lower portion of the trunk.

According to a preferred feature of the invention the gripping element comprises a pair of gripping elements which are in axial spaced relation to each other and are located in the region of the upper and lower end. According to an alternative preferred feature of the invention the gripping element extends between the upper and lower ends. According to a preferred feature of the invention the engagement of the trunk by the trunk gripping elements extend over a substantial portion of the surface of the trunk encircled by a respective gripping element.

According to a preferred feature of the invention the gripping elements each comprise a belt member which is movable to be received around at least a portion of the trunk and which is able to be tensioned to provide the gripping engagement of the trunk by the respective gripping element.

According to an alternative preferred feature of the invention the gripping elements each comprise an inflatable collar which is receivable around the trunk and connected to a source of fluid pressure to enable inflation of the collar to cause the collar to tightly engage the trunk. According to a preferred feature of the invention the collar is configured to at least limit the flow of fluid through the collar and around the trunk when inflated. According to a preferred feature of the invention the collar is formed of a plurality of bladders which are located around the central axis of the gripping means to support the trunk at angularly displaced locations around the trunk.

According to a preferred feature of the invention a plurality of gripping elements are supported in an angularly spaced relation to in use be located around the trunk and extend between the locations, each gripping element comprising a bladder which is and connected to a source of fluid pressure to enable inflation of the bladder to cause the gripping elements to jointly engage the trunk.

According to a preferred feature of the invention the bladders are connected with the source through a common fluid line whereby the connection to the fluid line provides restricted connection between the bladders.

According to a preferred feature of the invention wherein the upper and lower portions are separate from each other and are each supported from the base, the vibratory means associated with the upper portion.

According to a preferred feature of the invention wherein the trunk gripping member is formed as a member having a generally tubular configuration with an axial extent, said trunk gripping elements located on the inner face of the member, said member being formed as a plurality of segments separable along longitudinal axes of the member, a drive means adapted to cause relative movement of the segments between a closed position at which they cooperate to define a closed space and an open position at which position they define an entry into the space.

According to a preferred feature of the invention the member comprises two segments of generally semicircular cross-section, said segments being hinged at one side and separable at the other side.

According to a preferred feature of the invention the trunk gripping member is supported from the base by a resilient suspension which is adapted to permit - A - movement of the trunk gripping member relative to the base against a biasing force applied by the resilient suspension which will otherwise hold the gripping member in an at rest position. According to a preferred feature of the invention the resilient suspension comprises a plurality of resilient suspension elements located between the gripping member and the base to provide a substantially symmetrical support between the gripping member and the base. According to a preferred feature of the invention an engagement member is provided on the base and is movable into engagement with the gripping member to hold the gripping member substantially stationary relative to the base

According to a preferred feature of the invention the vibratory action of the vibratory means is capable of adjustment to vary the periodicity of the cyclic action and the magnitude of force applied to the trunk by the trunk shaking member. According to a preferred feature of the invention the vibratory member comprises a set of shafts supported from the trunk shaking member and positioned in use to be located around the trunk in a substantially symmetrical array, each shaft supporting an eccentric weight, said shafts being adapted to be rotate in unison from a drive means associated with the base. According to a preferred feature of the invention the degree of eccentricity of the weights on the shaft can be varied. According to a preferred feature of the invention each shaft supports a pair of eccentrically located weights wherein the degree of relative displacement between the weights can be varied. According to a preferred feature of the invention the drive means comprises a drive motor associated with each shaft and a control adapted to cause the rotation of the shafts to be synchronous relative to each other. According to a preferred feature of the invention the drive motor comprises a fluid powered motor.

According to a preferred feature of the invention the drive comprises a single drive motor which is drivingly connected to each shaft. According to a preferred feature of the invention the driving interconnection comprises a chain drive.

The invention will be more fully understood in the light of the following description of several specific embodiments. Brief Description of the Drawings

The description is made with the accompanying drawings of which;

Figure 1 is a schematic perspective view of a harvester according to the first embodiment;

Figures 2a, b and c are isometric views of the first embodiment illustrating the degree of variation of eccentricity of the weights of the tree shaking member;

Figures 3a and b illustrate the clamping engagement of the trunk affected by the tree shaking member and the tree gripping member by the first embodiment; and

Figure 4 illustrates the support for the harvester from a vehicle according to the first embodiment;

Figure 5 is a plan view of the second embodiment;

Figure 6 is an isometric view of the second embodiment;

Figure 7 is an isometric view of the third embodiment in its closed mode;

Figure 8 is an isometric view of the third embodiment in its open mode; and

Figure 9 is an illustration of the nature of the motion which is induced into a tree by each of the embodiments.

Detailed Description of Specific Embodiments

The embodiments are each directed to a harvester which is intended to be utilised for the harvesting of olives from trees and which utilises the practice of shaking the tree to loosen the olives from the trees but which do so without incurring significant damage to the trunk of the trees and/or the root system of the trees which has been a characteristic of prior harvesters which have applied a shaking action to the tree. The fruit harvester of the first embodiment as is illustrated at Figures 1 to 4 comprises a base 11 which is adapted to be able to be supported from an articulated boom 13 which in turn can be supported from a vehicle (see Figure 4). The base supports a tree gripping member which comprise an upper portion 15 and lower portion 17 interconnected by an upstanding column 19 whereby the portions 15 and 17 are vertically displaced from each other

Both the portions 15 and 17 are able to at least partially encircle a trunk of a tree and then grip the trunk to ensure a positive engagement with the tree in a manner which will not significantly damage the cambium and roots of the tree.

Both the portions 15 and 17 comprise a pair of parallel plate elements 21 and 23 which are supported in spaced vertical relationship from each other to provide space therebetween. Each of the plates 21 and 23 are supported from the column 19 and on their edge remote from the column 19 they are each are formed with a recess 25 which is configured such that the trunk of a tree can be located within the recess. The tree gripping means in both portions 15 and 17 is effected by means of a belt 27 supported from each portion. The belt 27 is supported at its ends from between the plates at the inner end of the recess 25. In addition at a position located adjacent the outer end of the recess 25 the plates support between themselves a pair of arm members 29 which are pivotally supported around a drive shaft 31 which extends between the portions 15 and 17. Support for the belt is effected through a set of rollers comprising a first pair of rollers 33 located at each end of the arms 29, a second pair of rollers supported between the plate members 21 and 23 and to either side of the recess and a third pair of rollers located 37 located at one side of the respective member. In addition the rear of each portion 15 and 17 supports a fluid operated cylinder 39 which is mounted transversely across the portion having its base fixed adjacent the third set of rollers 37. A fourth set of rollers 41 are supported from the outer end of the rod 43 of the cylinder whereby with expansion and contraction of the cylinder the fourth set of rollers are displaced with respect to the third set of rollers and transversely across the respective portion. As has been stated previously the belt 27 is fixed at its ends at the inner edge of the recess and the belt extends around each of the first pair of rollers 33 supported by the arms 29, the second pair of rollers 35 supported from the plates, and around the third and fourth set of rollers 37 and 41. On extension of the fluid operated cylinder 39 the belt 27 through its engagement with the first pair of rollers 33 causes the arms 29 to pivot inwardly towards each other at the shaft 31 such that the first rollers move towards each other which in turn brings the belt into engagement around the trunk.

In use and as shown at Figures 3A and B when the portions are to be engaged with the trunk of a tree the hydraulic cylinder 39 is in its contracted condition causing the first pair of rollers 33 and hence the arms 29 to be at their maximum spacing with respect to each other. On the tree trunk being located within the recess 25, the cylinder 39 is extended which causes the arms 29 to pivot towards each other and in so doing the trunk is retained in the recess by the belt 27 and the clamping action which is applied around the trunk by the belt 27 can then be varied in intensity according to the pressure applied to the fluid cylinder 39. The engagement of the trunk by the belts is over a considerable surface area which is defined by the width of the belt and the length of the belt which is in actual physical engagement with the trunk. In addition the engagement of the trunk by the belts enables some relative movement between the trunk together with the belt and the respective member depending upon the magnitude of the pressure applied through the fluid cylinder 39 and it does not comprise a rigid interconnection.

In addition the base 11 supports a drive motor 47 which is drivingly interconnected through a suitable chain drive to the shafts 31 which are rotatably received within the plates 21 and 23 of the trunk gripping member 15 and the trunk shaking member 21. On activation of the drive motor 47 the shafts will rotate in unison and in the same direction. Each of the shafts are provided at their ends proximate the upper portion 17 with a pair of eccentrically mounted weights 49 and 51 which are located adjacent the plates 21 and 23 respectively. The weights are of a semi-circular cross section and are supported eccentrically from the shaft 31. In addition the uppermost weights 51 are capable of being adjusted in their angular position on the respective shaft 31 whereby their position on the shaft 31 can be varied with respect to the respective lower weight 49 to vary the overall degree of eccentricity of the weights supported on each shaft. As a result the degree of eccentricity of the weights 49 and 51 can be varied between a position whereby each of the weights on each shaft are in an opposing relation to each other (as shown at Figure 2A) whereby the weights on each shaft are balanced with respect to each other and a position at which the weights are in a corresponding position on the shaft 31 (as shown at Figure 2C) at which the degree of eccentricity is maximised and any one of a range of immediate positions therebetween (one of which is illustrated in Figure 2B). In addition the weights are located on each of the shafts 31 such that on their rotation through the drive means 47 they are in phase with each other.

In the application of the harvester to the trunk of a tree as illustrated at Figure 3B whereby both of the portions are positively engaged with the trunk, the activation of the drive motor 47 results in rotation of the shaft 31 and depending upon the degree of eccentricity established by the weights 49 and 51 on each shaft, a cyclic vibratory motion is applied to the upper portion of the trunk of the tree by the uppermost portion whilst the lowermost portion remains substantially stationary and this is reinforced by the inertia of the lower portion which contains considerable mass due to the support provided by the drive for the shafts. As a result the tree is caused to be moved in the manner which is illustrated at Figure 9 where the trunk pivots about its base. As a result the root system of the tree is subjected to little vibratory motion whilst the upper portion of the tree containing the fruit is subjected to considerable vibratory motion. Furthermore the vibratory motion which can be applied to the upper portion of the tree can be varied by varying the speed of the rotation of the shaft 31 through the drive motor 47 and the degree of eccentricity between the weights 49 and 51. In addition it is envisaged that it will be possible to vary the degree of eccentricity of the weights 49 and 51 whilst the device is in operation such that the degree of shaking applied to the tree can be varied in accordance with the characteristics of the tree. The second embodiment of the invention which is illustrated at Figures 5 and 6 comprises a fruit harvester having a base 111 in the form of a support frame which is able to be supported from an articulated boom (not shown) which in turn can be supported from a vehicle (not shown). The base supports a tree gripping member 114 having an upper portion 115 and a lower portion 117. The tree gripping member 114 is of a generally tubular configuration and is subdivided into two halves along a central diametric axis. The two halves are pivotally interconnected at one side by a pair of pivot pins 116 whereby the two halves can be separated to provide access into the interior of the gripping member when closed (as shown at Figures 5 and 6) at which position it is able to encircle the trunk of a tree. The opening and closing of the two halves is effected by a hydraulic cylinder between the two halves in the region of the pivot pins 116.

Both the upper portion 115 and the lower portion 117 of the tree gripping member are provided with tree gripping means in the form of an inflatable collar 118 which is supported around the interior of tree gripping member 114 at the upper and lower ends. The collar 118 is divided into a plurality of segments which are interconnected by ducts of reduced diameter. Each of the collars 118 are connected to a source of hydraulic fluid or liquid which can be delivered into the collar 118 to effect their inflation.

The upper portion 115 comprises a pair of parallel plates 120 mounted to the upper end of the tree gripping member in parallel spaced relation while the lower portion 117 comprises a single plate 122 mounted proximate the lower end of the tree gripping member. The single plate is parallel to the plates 120 of the upper portion and each of the plates are of a square configuration. The plates 120 and 122 support between themselves a set of four shafts 124 located at each corner of the plates 120 and 122. The shafts 124 are parallel to each other and are located relative to each other such that when the tree gripping member is in the closed position as shown at Figures 5 and 6, the shafts are symmetrically located around the central axis of the tree gripping member. The lower plate 122 supports a set of four hydraulic motors 126 which are associated with the shafts such that the motors 126 are drivingly connected to the respective shaft 124. The hydraulic motors are controlled such that their rotation is synchronous. In addition each shaft 126 supports an eccentric weight 151 and the mounting of each weight to the respective shaft is such that the position of the weights around the respective shaft can be varied through a suitable control drive provided between each shaft 131 and the respective eccentric weight 151. In addition each eccentric weight is associated with a sensor (not shown) which is able to indicate the relative position of the sensor on the shaft.

The tree gripping member 114 is supported from the base 111 by a set of four springs 128 which are located at equi-distant intervals around the tree gripping member 114 and which extend between the base and the lower portion 117 of the tree gripping member. In addition an engagement means (not shown) is provided between the base and the tree gripping member 114 and is able to positively engage and support the tree gripping member 114 to prevent relative movement of the tree gripping member 114 with respect to the base 11.

The apparatus is associated with a control which is able to effect

• the opening and closing of the tree gripping member 114 to enable the tree gripping member to grippingly engage a tree;

• inflation and deflation each of the collars 118 which are provided in the upper portion 115 and the lower portion 117;

• control for the drive motors 126;

• the position of the eccentric weights on their shafts; and

• engagement and disengagement of the engagement means with the tree gripping member.

In addition the controller is associated with the sensors associated with each eccentric weight for determining the relative position of each of the eccentric weights with respect to each other and as a result the overall degree of eccentricity of the drive. The control is able to vary the relative positions of the weights with respect to each other to vary the overall eccentricity of the eccentric weights about the upper portion 115 and to monitor the degree of overall eccentricity as a result of the signal provided by the sensors. By utilisation of the control the position of the relative position of the eccentric weights with respect to each other can be varied in order to vary the degree of eccentricity and therefore the amount of shaking which is applied to the trunk of the tree by the upper portion 115 of the gripping portion.

Due to the axial spacing of the upper portion 115 from the lower portion 11_.7 and the rigid manner in which the tree gripping member is able to engage the trunk of the tree the shaking action is applied to the portion of the trunk of the tree which is above the lower portion 117. The lower portion 117 is held the portion substantially stationery relative to the upper portion and this is enhanced by the mass of the lower potion. By comparison the portion of the tree which is engaged by the upper portion 115 is caused to move in response to the force imposed upon it by the rotation of the eccentric weights 151 and the degree of shaking can be varied by varying the degree of eccentricity of the eccentric weights on the respective shafts 131 and/or the speed of rotation of the shafts. The motion which is induced to the tree is illustrated at Figure 9.

In use tree gripping member is brought into position beside a tree trunk by the articulated boom and the tree gripping member is opened. Once open the tree gripping member 114 can then be located such that the trunk of the tree is located within the centre of the tree gripping member and the tree gripping member 114 which is then closed. Throughout this stage the engagement means positively engages and supports the tree gripping member 14. Once in position around the tree the collars 118 are inflated in order that they tightly engage the trunk of the tree substantially throughout the circumference of the collar. Once the trunk is so engaged the engagement member is then released from the tree gripping member 114 and the hydraulic motors 126 are activated such that the shafts are caused to rotate in unison at the same speed and the degree of eccentricity of the eccentric weights can be varied according to the nature of the tree to which the tree gripping member 114 is engaged. With activation of the hydraulic motors 126 the upper portion 115 is caused to move because of the eccentricity of the weights and in so doing cause the trunk of the tree to shake correspondingly move. This shaking of the tree will result in the dislodgement of fruit from the tree. Whilst undergoing the shaking action the roots of the tree remain substantially stationary.

Once the tree has been shaken to the required amount the hydraulic motors 126 are deactivated engagement means is engaged with the tree gripping member 114 which is then opened and bought out of engagement of the tree trunk.

It is a characteristic of the second embodiment that the gripping force which is applied to the trunk of the tree by the collar 118 causes little damage to the trunk of the tree. This is as a result of the positive engagement effected by the inflatable collar and the use of hydraulic fluid or a liquid which provides little resilience in its support. Furthermore the forming of the collar 118 as a set of segments with limited communication between the segments serves to prevent the flow of liquid around the collar as a result of unequal forces being applied to the collar during the shaking action and therefore limit resultant movement of the tree trunk relative to the second portion.

The third embodiment is of a similar form to the second embodiment. The principal differences comprise the support provided between the tree gripping means and the tree and the drive for the shafts. In the case of the third embodiment the tree gripping means comprises a set of longitudinal bladders

224 which are supported from the inner face of the tree gripping member and extend for the length of the tree gripping member. A set of four bladders 224 are located in an equi-angular array around the central axis of the tree gripping member and they are connected to a common source of fluid pressure in a manner which limits or prevents the cross flow of fluid between the bladders.

In addition the shafts are driven from a common drive motor 247 through a set of one or more chains (not shown) which are drivingly connected to sprockets supported from each shaft. Each of the embodiments provide a tree harvester which can be utilised to maximise the degree of shaking that can applied to the tree according to the characteristics of the tree whilst maintaining the base of the tree substantially stationary. In addition the engagement of the trunk of the tree by the trunk gripping member is positive and extends over a significant portion of the surface area of the trunk and yet is also able to accommodate for some limited movement of the trunk relative to the main structure of the harvester.

It should be appreciated the scope of the present invention need not be limited to the particular scope of the embodiments described above and in particular need not be restricted to the harvesting of olives.

Claims

ClaimsThe claims defining the invention are as follows:

1. A harvester for harvesting tree borne fruits comprising a base supported or adapted to be supported from a vehicle, a trunk gripping member supported from the base, the gripping member being adapted to at least partially encircle the trunk and having an axial extent, the gripping member provided with a gripping element which is capable of being activated to grippingly engage the trunk of a tree at two vertically spaced locations to hold the trunk substantially stationary relative to the gripping member at the locations, the gripping element engaging a substantial portion of the perimeter of the trunk adjacent the gripping element, a vibratory means associated with the upper end of the gripping member to induce a cyclic lateral movement of the upper portion of the gripping member and the upper portion of the trunk engaged by the gripping element relative to the lower portion of the gripping member and the lower portion of the trunk.

2. A harvester as claimed at claim 1 wherein the gripping element comprises a pair of gripping elements which are in axial spaced relation to each other and are located in the region of the upper and lower end.

3. A harvester as claimed at claim 1 wherein the gripping element extends between the upper and lower ends.

4. A harvester as claimed at claim 1 or 2 or 3 wherein the engagement of the trunk by the trunk gripping elements extend over a substantial portion of the surface of the trunk encircled by a respective gripping element.

5. A harvester as claimed at claim 2 and claim 4 as dependant from claim 2 wherein the gripping elements each comprise a belt member which is movable to be received around at least a portion of the trunk and which is able to be tensioned to provide the gripping engagement of the trunk by the respective gripping element.

6. A harvester as claimed at any one of claims 1 to 4 wherein the gripping elements each comprise an inflatable collar which is receivable around the trunk and connected to a source of fluid pressure to enable inflation of the collar to cause the collar to tightly engage the trunk.

7. A harvester as claimed at claim 6 wherein the collar is configured to at least limit the flow of fluid through the collar and around the trunk when inflated.

8. A harvester as claimed at claim 6 or 7 wherein the collar is formed of a plurality of bladders which are located around the central axis of the gripping means to support the trunk at angularly displaced locations around the trunk.

9. A harvester as claimed at any one of claims 1 to 4 wherein a plurality of gripping elements are supported in an angularly spaced relation to in use be located around the trunk and extend between the locations, each gripping element comprising a bladder which is and connected to a source of fluid pressure to enable inflation of the bladder to cause the gripping elements to jointly engage the trunk.

10. A harvester as claimed at any one of claims 8 or 9 wherein the bladders are connected with the source through a common fluid line whereby the connection to the fluid line provides restricted connection between the bladders.

11.A harvester as claimed at any one of claims 1 to 9 wherein the upper and lower portions are separate from each other and are each supported from the base, the vibratory means associated with the upper portion.

12. A harvester as claimed at any one of claims 1 to 10 wherein the trunk gripping member is formed as a member having a generally tubular configuration with an axial extent, said trunk gripping elements located on the inner face of the member, said member being formed as a plurality of segments separable along longitudinal axes of the member, a drive means adapted to cause relative movement of the segments between a closed position at which they cooperate to define a closed space and an open position at which position they define an entry into the space.

13. A harvester as claimed at claim 12 wherein the member comprises two segments of generally semicircular cross-section, said segments being hinged at one side and separable at the other side.

14. A harvester as claimed at claim 12 or 13 wherein the trunk gripping member is supported from the base by a resilient suspension which is adapted to permit movement of the trunk gripping member relative to the base against a biasing force applied by the resilient suspension which will otherwise hold the gripping member in an at rest position.

15. A harvester as claimed at claim 14 wherein the resilient suspension comprises a plurality of resilient suspension elements located between the gripping member and the base to provide a substantially symmetrical support between the gripping member and the base.

16.A harvester as claimed at claims 14 or 15 wherein an engagement member is provided on the base and is movable into engagement with the gripping member to hold the gripping member substantially stationary relative to the base

17. A harvester as claimed at any one of the preceding claims wherein the vibratory action of the vibratory means is capable of adjustment to vary the periodicity of the cyclic action and the magnitude of force applied to the trunk by the trunk shaking member.

18. A harvester as claimed at claim 17 wherein the vibratory member comprises a set of shafts supported from the trunk shaking member and positioned in use to be located around the trunk in a substantially symmetrical array, each shaft supporting an eccentric weight, said shafts being adapted to be rotate in unison from a drive means associated with the base.

19. A harvester as claimed at claim 18 wherein the degree of eccentricity of the weights on the shaft can be varied.

20. A harvester as claimed at claim 18 or 19 wherein each shaft supports a pair of eccentrically located weights wherein the degree of relative displacement between the weights can be varied.

21. A harvester as claimed at any one of claims 17 to 20 wherein the drive means comprises a drive motor associated with each shaft and a control adapted to cause the rotation of the shafts to be synchronous relative to each other.

22.A harvester as claimed at claim 21 wherein the drive motor comprises a fluid powered motor.

23.A harvester as claimed at any one of claims 17 to 20 wherein the drive comprises a single drive motor which is drivingly connected to each shaft.

24.A harvester as claimed at claim 21 wherein the driving interconnection comprises a chain drive.

25. A harvester substantially as herein described.