WO2024115405A1

WO2024115405A1 - Slab harvester

Info

Publication number: WO2024115405A1
Application number: PCT/EP2023/083199
Authority: WO
Inventors: Zhanna Rudakova VAN VUUREN
Original assignee: Van Vuuren Machines BV
Current assignee: Van Vuuren Machines BV
Priority date: 2022-11-30
Filing date: 2023-11-27
Publication date: 2024-06-06
Anticipated expiration: 2025-05-30
Also published as: NL2033646B1

Abstract

The invention concerns a slab harvester (10) for harvesting slabs (48) of a crop substrate, such as sedum substrate or sod, from the ground (18), comprising a first cutting unit (30) configured for cutting at least one longitudinal edge (24) of a strip (36) of crop substrate; a second cutting unit (46) configured for providing a transverse cut in the strip (36) of crop substrate, thereby establishing a cut slab (48) of crop substrate from the strip (36) of crop substrate; a separation head (41) configured for separating the strip (36) of crop substrate from the ground (18); a stacking unit (52) configured for stacking cut slabs (48) of crop substrate in a stack arrangement; a conveyor system (42, 44) configured for receiving and conveying the strip (36) of crop substrate and/or cut slabs (48) from the ground (18) to the stacking unit (52).

Description

SLAB HARVESTER

The present invention relates to a slab harvester for harvesting crop substrate, such as sods or sedum substrate from the ground, such as a turf field or a field of cultured sedum respectively.

Sod harvesters for harvesting sods, whether in rolled shape or in flat shape, are known. A known type of sod harvester commercially available from the present applicant for harvesting turf while moving at a constant speed over a turf field, first provides parallel longitudinal cuts by coulter discs in the turf field thereby forming a strip and then a transverse cut in the strip by a falling knife thereby cutting a slab from the strip. The slab thus cut from the turf field is separated from the ground and received by an inclined conveyor, which transports the slab to a stacking unit. During transport on the inclined conveyor the cut slab may be wound into a rolled shape. The stacking unit provided with a movable lifting gripper provided with hooks or teeth to insert in the slabs lifts one or more slabs (rolled or flat mat) from the conveyor and collects them on a transport carrier like a pallet, in a stacked arrangement. Once the transport carrier is fully loaded, the transport carrier is put down on the field, collected and transported further, while an empty transport carrier is reloaded either by hand or automatically by a carrier injector from a carrier storage present on the sod harvester.

W02006/081654A1 has disclosed a sod harvester which, after harvesting sod, can pick up the longitudinally and transversely cut sod and stack the cut slabs in flat condition on a pallet. In an embodiment thereof a sod carrier is suspended from a movable gantry and serves to pick-up the sod from a conveyor, after which the gantry travels laterally to a position over the pallet. The sod carrier then deposits its layer of sod on the pallet. The sod carrier includes a number of pairs of biased clamps, which extend parallel to each other at the underside of the sod carrier. A series of hooks may be added to the clamps, to provide improved grip by the sod carrier on the sod strips.

In recent times increasing attention has been paid to greening the living environment in view of sustainability. One of the aspects thereof concerns the provision of a vegetation layer of living plants like one or more sedum species, a succulent, on parts of buildings, like roofs. Benefits of this vegetation layer include inter alia protection of the roof from UV radiation thereby improving the (roof) service life, a habitat for animals, like birds and insects, thereby increasing biodiversity, air purification thereby improving the urban air quality and water retention thereby improving control of run off rain water, heat and sound insulation, and low maintenance costs. Nowadays sedum combined with its substrate (hereinafter ‘sedum substrate’) is commercially available in various forms such as flat mats, rolled strips and in trays. Sedum for commercial supply is typically grown in the open field similar to turf, but harvested manually. Sedum substrate differs from turf in that inter alia the root structure of sedum is more loose making the sedum substrate vulnerable, sedum is typically grown on a mixed substrate of earth and additives, for example coconut (husk), in which substrate usually a plastic netting as a reinforcement is incorporated, instead of only soil. Typically, also a (plastic) separation foil is arranged on the bare earth, on which the sedum in the mixed substrate is to be grown. These differences complicate harvesting, transport and handling of sedum substrate compared to turf. A known alternative is culturing sedum in trays on the field. Such trays provide support for the sedum substrate, thereby increasing manipulability. However, growing itself as the trays need to be regularly arranged on the field and after growth collecting of the trays is laborious and therefore increases the total costs.

Now, it has appeared that known sod harvesters for mechanically harvesting turf as rolled or flat slabs in open field cultivation cannot be used for harvesting sedum substrate in the same way, mainly as a result of the difference in substrate root structure between sedum and turf, the presence of a reinforcing netting and/or the frequent presence of a plastic separation foil. In particular it has appeared that stacking sedum substrate slabs, comprising engaging a slab of sedum substrate from above by the lifting gripper and lifting it, despite the presence of a reinforcing netting, may cause sagging of the slab and due to its less solid structure tearing, in particular in case of stacking the slabs as flat mats. This risk is even more pronounced, when the lifting gripper is operated to drop the one or more rolled slabs or the one or more mats from a certain height on the rolls or mats already stacked on the transport carrier. Furthermore it has appeared that the transverse cut made by the falling knife and necessary to cut a strip of sedum substrate in the width direction may be incomplete due to the root structure of sedum and the reinforcing netting, as a result of which a cut slab may have frayed edges, in particular front and rear edges, and inappropriate dimensions resulting in reduced quality, or even a cut slab may be not fully separated from the longitudinally cut strip and remain partly connected to the strip. In addition to the inevitable final rejection of a slab having inappropriate dimensions or quality, further processing such as stacking by the harvester is impeded, and disruptions in the harvesting process and in the operation of the harvester may occur.

Furthermore, if a plastic separation foil is present, transverse cutting a slab of sedum substrate, while it is in contact with the foil, will result in waste parts of plastic having dimensions of the slab, which waste parts need to be collected individually in order to prevent damage and contamination of the field and its environment.

In view of these difficulties in general harvesting of sedum substrate from an open field is performed manually - at least partly -, which is labour intensive, heavy, and costly. Therefore there is a general need for a device that allows mechanical harvesting of vulnerable crop substrate slabs, like sedum substrate, from open fields.

The present invention aims at solving this need or at least to provide an alternative slab harvester for harvesting slabs of crop substrate, in particular vulnerable crop substrate, like sedum substrate

The present invention aims at the provision of a slab harvester that does not suffer from the above drawbacks or at least to a lesser extent.

An object of the present invention is to provide a slab harvester that allows to process vulnerable crop substrate slabs with a reduced risk of damaging, in particular during stacking of crop substrate slabs in a flat shape, such as rectangular mats.

Another object of the invention is to provide a slab harvester that allows to stack cut slabs of crop substrate, while maintaining the integrity of the vulnerable slabs.

Yet another object is to provide a slab harvester that allows to provide a reliable transverse cut through a reinforced substrate thereby ensuring the cut crop substrate slabs to possess appropriate dimensions thereby improving quality.

Still another further object of the invention is to provide a slab harvester that allows to collect the separation foil.

A further object of the invention is to provide a slab harvester, wherein the various operations of its components are controlled and synchronized with the movement speed of the harvester over the field.

Yet another object of the invention is to provide a slab harvester that allows to monitor at least one dimension of the cut slab in order to control its size.

According to a first aspect, the invention provides a crop substrate slab harvester as defined in claim 1.

The crop substrate slab harvester according to this first aspect of the invention generally comprises a frame provided with one or more supporting wheels, which frame is mounted, for example (releasably) coupled, to a driven vehicle, such as a tractor or other agricultural device. In an alternative embodiment the crop substrate slab harvester may have its own wheeled chassis, driver’s cab and drive for moving around a field. A first cutting unit is configured for cutting at least one longitudinal edge, typically both longitudinal edges, of the strip to be formed from the field of crop substrate. A second cutting unit is configured for providing a transverse cut (in a direction transverse to the longitudinal direction of the strip) in the strip of crop substrate, in particular once a predetermined length of strip has passed to produce a cut slab of crop substrate from the strip of crop substrate. The second cutting unit may be provided upstream of a separation head. The separation head positioned downstream of the first cutting unit is configured for separating the strip from the ground, and if present, also from a separation foil, that remains on the ground. The slab harvester is provided with a conveyor system configured for receiving and conveying the strip of crop substrate and/or cut slabs from the ground to a stacking unit. Generally the conveyor system comprises a first conveyor system, typically comprising at least one endless belt conveyor upwardly inclined with respect to the horizontal ground, that receives the separated strip and conveys it to a second conveyor system, typically comprising one or more endless belt conveyors, which second conveyor system conveys the strip and slabs cut therefrom further to the stacking unit. In an embodiment the second cutting unit is provided at the transfer position from the first conveyor system to the second conveyor system, as will be further explained hereinbelow. The slab cut from the strip is advanced by the second conveyor system to the stacking unit, which stacking unit is configured for receiving the cut slabs from the (second) conveyor system and stacking thereof on a suitable transport carrier, such as a pallet, in a stack arrangement.

According to an aspect of the invention the stacking conveyor comprises a stacking conveyor, preferably horizontally arranged, configured for receiving and conveying thereof a cut slab of crop substrate (either a rolled slab or a flat mat) from the (second) conveyor system, a collection carrier positioned at a lateral side of the stacking conveyor, configured for receiving cut slabs of crop substrate in a stack arrangement, a slab support configured supporting a slab of crop substrate from below and configured for moving the slab of crop substrate in a direction transverse to the conveying direction of the stacking conveyor from a loading position to an unloading position, a gripper system configured for gripping from above a cut slab from the stacking conveyor and transferring the cut slab onto the slab support in the loading position and configured for transferring the cut slab from the slab support to the collection carrier in the unloading position. By supporting the cut slab of crop substrate from below by the slab support during transfer from the stacking conveyor to the collection carrier sagging is suppressed and as a result the risk of damaging the crop substrate slab is reduced and the structural integrity of the crop substrate slab of during stacking is retained.

In an embodiment the slab support may be an endless belt conveyor.

In an embodiment the stacking unit comprises a transfer frame having transfer frame beams extending from the stacking conveyor in a direction transverse to the conveying direction of the stacking conveyor to the collection carrier, a slab support plate movably supported by the transfer frame beams and configured for reciprocating movement in a direction transverse to the conveying direction of the stacking conveyor between the loading position, wherein the gripper system slides a cut crop substrate slab from the stacking conveyor onto the slab support plate, and an unloading position, wherein the gripper system slides the cut crop substrate slab from the slab support plate onto the collection carrier.

In a further embodiment thereof in the loading position the slab support plate extends beneath the stacking conveyor, in particular beneath the upper conveying part of an endless conveyor belt as stacking conveyor and above the return part thereof. By arranging the slab support plate essentially at the height of the stacking conveyor, in particular at the level of the upper conveying part of an endless belt conveyor as stacking conveyor, the difference in height between the stacking conveyor and the slab support plate is kept small, allowing smooth transfer from the cut slab from the stacking conveyor to the slab support, in particular the slab support plate.

In an embodiment the gripper system may comprise a gripper, which is configured for movement in a direction transverse to the conveying direction of the stacking conveyor, e.g. mounted to the slab support plate or also movably arranged on the stacking frame beams. In an embodiment the gripper system comprises a gripper having an extendable gripping arm, e.g. telescopically arranged arms or hinged arms, wherein the gripper is mounted at a fixed position of the harvester, e.g. at the lateral side of the collection carrier opposite the stacking conveyor. Other positions for such a gripper system comprising a gripper having an extendable gripping arm are movably supported on the transverse frame beams of the stacking frame and mounted on the movable slab support, in particular the slab support plate for co-movement therewith.

In another embodiment the gripper system comprises a first gripper, preferably mounted on the slab support plate, configured for moving in a direction transverse to the conveying direction of the stacking conveyor, and for gripping from above a cut slab from the stacking conveyor and transferring it to the slab support plate, and a second gripper, mounted on the harvester, e.g. at the end of the frame beams opposite to the stacking conveyor, preferably at a fixed position, and configured for gripping from above a cut slab from the slab support plate and transferring it to the collection carrier.

In this embodiment, the first gripper engages the slab from above and by moving the first gripper in the transverse direction to the conveying direction of the stacking conveyor the slab is forced to slide from the stacking conveyor onto the slab support plate. The slab support plate is essentially arranged at the height of the stacking conveyor, such that the difference in height between the stacking conveyor and the slab support plate is kept small. Preferably in the loading position the slab support plate extends beneath the upper conveying part of an endless stacking conveyor. Next the slab support plate loaded with the cut slab moves along the frame beams to a position above the collection carrier, e.g. loaded with a transport carrier such as a pallet. Preferably, the first gripper is arranged to move simultaneously with the slab support for continued holding the cut slab on the slab support.

At the unloading position at a height above or adjacent the uppermost slabs on the collection carrier, and when the first gripper has released the cut slab on the slab support plate, the second gripper is operated to engage the slab. Next the slab support plate is returned to its loading position at the stacking conveyor, thereby sliding the slab hold by the second gripper from the slab support plate on top of the collection carrier or on top of the slabs already present on the collection carrier. The cycle is repeated on a new slab that has arrived on the stacking conveyor.

Due to the sliding movements and supported transfer by the slab support from the stacking conveyor to the collection carrier the risk of damaging the vulnerable slabs is reduced, thereby ensuring the structural integrity thereof and thus slab quality.

In an embodiment the second gripper may be movably mounted to the frame beams, which is beneficial if the cut slabs are to be mounted in two or more stacks on the collection carrier.

The slab support plate may be slidingly arranged on the beams or supported by wheels. The driving mechanism for reciprocating movement of the slab support plate and/or the first gripper and/or second gripper may comprise a (pneumatic) piston cylinder assembly, a rack pinion system, a chain or belt drive and the like.

The collection means typically is provided with a support for a transport carrier, such as a pallet, which support is displaceable in the height direction, such that the top of the uppermost stacked mat or roll can be maintained at a predetermined level with respect to the slab support, allowing to keep the height difference between the top of the slab support and the top of the uppermost stacked mat or roll small and thus an easy sliding transfer.

In an embodiment the slab harvester also comprises a transport carrier injector, configured for discharging a loaded transport carrier such as a pallet onto the ground and reloading an empty transport carrier from a transport carrier storage on the crop slab harvester, in particular the collection means of the stacking unit. A pallet injector is known per se from sod harvesters, e.g. those commercially available from the applicant.

In an embodiment a gripper of the gripper system, in particular the above mentioned first gripper and/or second gripper, comprises an engagement element, such as a gripper beam, extending in the conveyance direction of the stacking conveyor, configured to be movable between an engaging position for engaging the cut slab of crop substrate and an open position, wherein there is no contact with a crop substrate slab (mat or roll), e.g. using a (hydraulic) piston cylinder assembly.

In order to ensure a firm grip on the mat or roll the face of an engaging element configured for engaging the cut slab from above is provided with a plurality of projections, such as pins or teeth. In the engaging position the projections are inserted to a certain extent in the mat or roll. The projections may be curved, in particular they may have a curvature according to a relatively small circle arc having a radius around the rotation axis of the gripper element for rotation between the gripping position and open position thereof and vice versa. Such curved projections, once inserted in the slab, serve to hold the slab firmly and to prevent damage, even when there is a small height difference between the stacking conveyor and the slab support and/or the slab support and the top of an already stacked slab during transfer. In an embodiment the gripper system, in particular the first and second gripper thereof, comprises a (first and second respectively) piston cylinder assembly for moving the engagement element between the engagement position and the open position.

According to another aspect of the invention the second cutting unit is arranged at a position on the conveyor system, where the strip of crop substrate has been separated from the ground.

In a further embodiment thereof the harvester, in particular for harvesting a slab of vulnerable crop substrate such as a sedum substrate, comprises a first conveyor system configured for receiving and conveying a strip of crop substrate separated from the ground by the separation head; wherein the second cutting unit is arranged downstream end of the first conveyor system at the transfer position from the first conveyor system to a second conveyor system, wherein the second conveyor system is arranged downstream of the second cutting unit and is configured for receiving the strip of crop substrate and conveying thereof and cut slabs of crop substrate; wherein the second cutting-unit comprises a cutter frame having a plurality of driven circular cutting elements that are arranged transversely to the conveying direction of the strip of crop substrate and adjacent to one another, and that are configured for movement in a first direction transverse to the conveying direction in cutting contact with the strip of crop substrate, thereby cutting a slab of crop substrate from the strip of crop substrate in the width direction thereof and configured for movement in a second direction, opposite to the first direction, at a height above the first conveyor system and the second conveyor system without contacting the strip of crop substrate.

According to this aspect of the invention the second cutting unit that is arranged at the transfer position between the first conveyor system and the second conveyor system, comprises a cutter frame to which a plurality of adjacent circular cutting elements are mounted such that these are rotatable in a direction parallel to the transverse direction. In other words the axes of rotation of these cutting elements are parallel to the conveyance direction of the first and second conveyor systems. The plurality of cutting elements preferably extend almost the full width of the strip or even beyond the longitudinal strip edges. Typically the cutting elements are oriented perpendicular to the supporting faces of the first conveyor system and the second conveyor system. The cutting elements are mounted to the cutter frame, allowing movement of the cutting elements in a first (transverse to the conveying direction) direction while contacting the strip, such that a strip can be cut over its full width from one longitudinal edge thereof to the other parallel longitudinal edge of the strip by the simultaneous operation of the cutting elements. The cutting elements are also mounted to the cutter frame allowing movement in a second direction, opposite to the first direction, at a height above the first conveyor system and the second conveyor system without contacting the strip of crop substrate by the cutting elements, such that an advancing strip end can pass freely below the cutting elements, until a next cutting operation of the second cutting unit. By having a plurality of cutting elements in a side by side arrangement in the transverse direction, preferably extending over essentially the full width or beyond, only a limited movement in the first (transverse) direction, e.g. in the order of half the diameter in case of circular cutting elements, is necessary to establish a complete transverse cut through the strip of crop substrate. This limited transverse movement requires less time to complete the transverse cut compared to a single cutting element of same dimensions (e.g. same diameter). This is important as the strip is continuously supplied by the first conveyor system to the position of the second cutting unit. For productivity, the transverse cutting operation should have a short duration, otherwise the cutting elements would block the continuously fed strip that as a result of the obstructing cutting elements would wrinkle and fold, most times upwardly, which deforms the crop substrate and/or provide an oblique transverse cut, as has appeared upon using a single cutting element. Wrinkling and/or folding involves the risk of damaging, tearing or even breaking of the crop substrate, thereby deteriorating the slab integrity and/or shape and as a result decreasing manipulability and/or quality thereof. A single rotating cutting element that has to move in the first transverse direction over the full width in order to provide the transverse cut would also require more time thereby necessitating a slower speed (or temporarily halting) of the first conveyor system and thus of the towing vehicle, and thus the harvesting capacity would be seriously affected. The cutter frame of the second cutting unit is also configured for moving in the upward direction with respect to the first conveyor and second conveyor system in order to allow free passage of the strip beneath the cutting elements. During harvesting the rotating cutting elements perform a cyclic movement in the transverse and height direction. Additionally, the transverse cutting operation by the second cutting unit is performed on the strip at a position, where the strip has been separated from the separation foil, if any, so that the separation foil cannot be cut to pieces by the second cutting unit, which pieces would need to be collected separately. In the invention, such cut foil pieces cannot disturb the operation of the harvester, e.g. getting stuck in one of the conveyors and/or second cutting unit. Therefore the crop harvester according to this aspect of the invention provides for a safe and reliable operation thereof in mechanically harvesting of crop substrate slabs from a culturing area, such as an open field. In an embodiment of the second cutting unit the plurality of driven cutting elements are mounted on a movable cutting unit subframe, that is movably mounted to a fixed cutting unit subframe. The movable subframe is displaceable in the first and second direction, as well as in the height direction, with respect to the fixed subframe. Preferably, the cutting unit comprises two movably configured subframes: a first subframe configured to be movable in the height direction with respect to a fixed subframe, a second subframe to which the cutting elements are mounted, configured to be movable in the transverse direction with respect to the first subframe.

Driving of the movable cutting unit subframe(s) may be accomplished by a suitable drive, such as a rack-and-pinion system or electric driven carriage to which the subframe(s) is (are) mounted. In a preferred embodiment the movable cutting unit subframe(s) are movably mounted by one or more piston cylinder assemblies configured for moving a movable subframe in the first and second direction and configured for moving a movable subframe in the height direction respectively. In an embodiment thereof the piston cylinder assemblies may be hydraulic assemblies.

In an embodiment the cutting elements are configured for co-rotation in the first direction of the subframe. Preferably each cutting element has its own drive, each of which is synchronously driven in a controlled manner.

In an embodiment the cutting elements are circular blades provided with a diamond cutting edge at the circumference of the blades.

In an alternative embodiment of the second cutting unit having a single cutting element in addition to the above subframes configured for movement in the height direction and transverse direction respectively, a further subframe configured to be reciprocating movable in the conveyance direction is contemplated.

If undesired excess wrinkling and/or damage to the strip of crop substrate occurs due to the transverse cutting operation by the cutting elements, the first conveyor system may be temporarily halted, while the towing vehicle keeps on moving, by having a buffer between the first cutting unit and the second cutting unit, which buffer is configured for temporarily accumulating the strip of crop substrate that is being conveyed from the first cutting unit. For example, the strip of crop substrate may be guided over a driven roll positioned between the first cutting unit and the first conveyor system and spaced apart therefrom. Upon halting the first conveyor system, the driven roll continues to rotate dependent on the speed of the towing vehicle. Simultaneously the part of the strip of crop substrate in front of the second cutting unit may be held at a fixed position on the halted first conveyor means, e.g. by means of an engaging arm that is movable between an engaging position wherein the engaging arm engaging the strip of crop substrate at a position upstream of the cutting elements and a nonengaging position wherein the engaging arm is raised allowing the strip to pass beneath it. In an embodiment thereof the engaging arm is fixed to the movable cutting subframe, in particular the first subframe as discussed above. On performing the transverse cut the strip is allowed to hang loosely over the driven roll, preferably at the upstream and downstream side thereof. Once the transverse cutting is completed the second cutting unit is lifted to its position allowing free passage of the strip of crop substrate thereby also releasing the engaging arm from the crop substrate. The first conveyor system is actuated again, typically at a speed slightly higher than the speed of the towing vehicle, thereby straightening the hanging strip of crop substrate. The sedum substrate is allowed to slip a bit on the first conveyor, but without causing damage thereto.

In a further aspect of the invention a crop substrate slab harvester is provided with a foil collector, configured for collecting used (plastic) separation foil from the ground, wherein preferably the second cutting unit is provided at a position on the conveyor system, as explained above. By collecting the used separation foil, typically cut in a strip by the first cutting unit that provides at least one longitudinal cut, and once the strip of crop substrate is removed from the separation foil, blowing away, tearing into pieces, and the like is effectively prevented. Such a foil collector, in particular a coiler, may be applied in every type of harvester that is intended for harvesting crops, plants and the like that are grown in a substrate using a separation foil between substrate and the lower underground. Thus this aspect of the invention provides a harvester, configured for harvesting a crop grown in a substrate using a separation foil, which harvester is provided with a foil collector, configured for collecting used separation foil, preferably in strip shape.

In an embodiment thereof the coiler comprises a rotatably arranged foil winding reel having a rotary axis in the traverse direction in the transverse direction with respect to the driving direction of the harvester, configured for winding the separation foil from the ground, as well as a reel drive configured for driving the foil winding reel. During forward movement of the crop substrate slab harvester the used foil is engaged by the reel on the ground and is picked up, thereby avoiding the need of separate collection thereof. Preferably, the used separation foil collector, in particular the above coiler, is comprised in the crop slab harvester of the first aspect of the invention.

It has appeared that the stacking operation, in particular the cycle time for stacking a mat in the stacking unit, can be a limiting factor for the capacity of the crop substrate harvester compared to the other components. Rolls are typically wound from the slab at a position near the transfer position from the conveyor system, generally the second conveyor system thereof, to the stacking conveyor, and could be buffered on the stacking conveyor, e.g. three or more, which subsequently are gripped together by the gripper system and while being supported on the slab support they are transferred to the transport carrier. For flat mats this buffering capacity of a single stacking conveyor is not available. In order to create sufficient time for a stacking cycle, the speed of the second conveyor system may be temporarily increased compared to the speed of the first conveyor system, thereby spacing apart a cut slab from the leading edge of the strip. This increase in speed will also flatten any folds that have occurred in the strip due to hold-up of the leading edge when executing the traverse cutting operation by the second cutting unit. Generally the first conveyor system will comprise a single conveyor. Typically the conveyors of the first conveyor system, the second conveyor system and the stacking conveyor are endless belt conveyors. The belt itself may be composed of a plurality of relatively small belts in a side by side arrangement. The conveying surface may be provided with tiny projections for extra grip on the crop substrate strip and/or slab.

In an embodiment of the crop slab harvester according to the invention the second conveyor system comprises at least two subconveyors in series, configured for establishing a distance between cut slabs of crop substrate from the second cutting unit to the stacking unit. The second conveyor system according to this embodiment allows the spacing between slabs in the crop slab harvester to be established in a controlled manner. Because of the controlled spacing, the stacking unit can be used to pick up a cut slab from the stacking conveyor and stack it on the collection carrier of the stacking unit, before a subsequent cut slab arrives at the stacking conveyor from the second conveyor system.

A controller is configured for controlling the operation of the actively controlled harvester components based on signals received from one or more sensors, configured for detecting the presence and/or position of a crop substrate strip end and/or a cut slab of crop substrate on the second conveyor system and the stacking unit.

Typically the actively operated components, including first conveyor system, second cutting unit, second conveyor system, stacking unit, optional separation foil collecting means, of the slab harvester are controlled by the controller, depending on the forward speed of the harvester, such as the towing vehicle.

Typically the controller is configured for setting a constant speed of the harvester, and for coordinating the operation of the other components, in particular the speed of the first conveyor system, cyclic movement of the second cutting unit, speeds of the subconveyors of the second conveyor system, and the stacking unit, e.g. the speed of the stacking conveyor and operation of the gripper system and slab support.

In an embodiment the sensors configured for detecting the presence of the strip end or slab in the harvester are typically positioned at least at the transfer from the first subconveyor to the second subconveyor of the second conveyor system, at the transfer from the second subconveyor of the second conveyor system to the stacking conveyor, and at the downstream end of the stacking conveyor.

In an embodiment two such sensors, spaced apart e.g. about 10-30 cm, such as 20 cm, in the conveying direction, are positioned at the downstream end of the stacking conveyor. The upstream sensor thereof initiates a controlled deceleration thereby allowing to more accurately position the cut slab on the stacking conveyor upon halting the stacking conveyor, triggered by the second downstream sensor. In another embodiment a sensor sensing the absence of a slab at the transfer position from the second conveyor to the stacking conveyor can trigger the controlled deceleration.

Generally the controller is configured to drive the first conveyor system at a speed equal to the forward speed of the slab harvester over the ground, and to drive the second conveyor system and stacking unit in order to establish a spacing between cut slabs on the second conveyor system by performing a cycle of accelerating and decelerating the subconveyors of the second conveyor system and the stacking conveyor.

E.g. the first subconveyor of the second conveyor system is driven at an increased speed such as three times the speed of the first conveyor system. Upon sensing the leading edge of the strip at the transfer position of the first subconveyor to the second subconveyor the speed of the first subconveyor is decelerated to the speed of the first conveyor system. The cutting operation by the second unit is performed on the crop substrate strip thereby producing a crop substrate slab. Directly after the second unit has performed its cutting movement in the first direction, the first subconveyor is accelerated to the increased speed, even if the cutting elements are not yet raised. A little hold up of the new leading end of the strip by the lowered cutting elements may occur. When the cutting elements are raised, this hold up is compensated by the increased speed of the first subconveyor and the strip is flattened.

During further conveyance the new strip end will slip on the first subconveyor, until the new leading end of the strip is detected by the sensor at the transfer position of the first subconveyor to the second subconveyor. This subcycle of adjusting the speed of the first subconveyor and driving of the second cutting unit is repeated continuously.

The second subconveyor is driven at the increased speed of the first subconveyor of the second conveyor system. Upon sensing the front end of the slab by the sensor at the transfer position of the second subconveyor to the stacking conveyor of the stacking unit, the second subconveyor is decelerated to an intermediate speed in between the increased speed and the speed of the first conveyor, such as two times the speed of the first conveyor. Upon sensing the rear end of the cut substrate slab by the sensor at the transfer position of the second subconveyor to the stacking conveyor of the stacking unit, the second subconveyor is accelerated to the increased speed until the front end of a subsequent slab is detected at the sensor at the transfer position of the second subconveyor to the stacking conveyor. This subcycle of the second conveyor is repeated continuously.

The stacking conveyor of the stacking unit is driven at the intermediate speed. Upon sensing the front end of the slab by the upstream sensor of the two sensors at the downstream end of the stacking conveyor, the speed of the stacking conveyor is decelerated to a slow speed such as half the speed of the first conveyor system. Upon sensing the front end of the slab by the downstream sensor of the two sensors at the downstream end of the stacking conveyor, the speed of the stacking conveyor is decelerated to zero and the stacking conveyor is halted. The slab is transferred from the stacking conveyor to the collection means by the gripper system. Upon removal of the slab from the stacking conveyor, the stacking conveyor is accelerated to the intermediate speed. This subcycle of the stacking conveyor and gripper system is repeated continuously. Based on the speed of the respective conveyor and lapsed time from the cutting operation of the second cutting unit the sensors allow to determine the length of the cut slab, and if its calculated length is outside a predetermined range to reject that slab. For rejection purposes a further reject conveyor may be provided adjacent the downstream end of the stacking conveyor, configured for receiving a slab to be rejected from the stacking conveyor and discharging thereof, e.g. on the ground or into a bin. If needed the reject conveyor may be used as a temporarily buffer position in case of failure or distortion of the stacking unit, e.g. the grippers, and/or transport carrier injector, if present. Thus in an embodiment the harvester comprises a reject conveyor downstream of the stacking conveyor, configured for receiving a slab of crop substrate, wherein the controller is configured for determining a slab length from signals received from the sensors, and driving the stacking conveyor and reject conveyor if the determined slab length is outside a predefined range. E.g. the slab has a desired length of 600 - 1200 mm and a width of 400 up to 800 mm. Typically the dimensions of the subconveyors of the second conveyor system and the stacking conveyor of the stacking unit are adapted to the size of the slab.

It will be clear that the aspects of a foil collector, configured for collecting a separation foil, can be similarly applied to other types of harvesters, where a crop is cultured in the open field using a separation foil, as well as to different substrate harvesters with other type(s) of conveyors, second cutting unit and/or stacking unit than the ones discussed above.

The same applies to the method and system of multiple conveyors for substrate handling (sedum, turf) that are controlled to carry out a cyclic operation of accelerating and decelerating in order to establish spacing between subsequently conveyed slabs, in particular where the slabs are to be stacked as flat mats.

It will also be apparent that the monitoring method and system for determining the length of a cut substrate slab using sensors and rejection of slabs having a length outside a predefined range can be used for substrate slab harvesters in general.

This stacking unit can also be used for handling trays, wherein a crop substrate is grown in trays arranged on the field. In that case the first and second cutting units for cutting a strip longitudinally and in in transverse direction, and separation head, are omitted. The invention is further illustrated by means of the attached drawing, wherein:

Fig. 1 diagrammatically shows an embodiment of a crop substrate slab harvester according to the invention in side view;

Fig. 2 diagrammatically shows the embodiment of the harvester of Fig. 1 in top view; Fig. 3 diagrammatically shows an embodiment of a second cutting unit of a crop substrate slab harvester according to the invention in more detail;

Fig. 4 diagrammatically shows an embodiment of a stacking unit of a crop substrate slab harvester according to the invention; and

Fig. 5 diagrammatically shows an embodiment of a buffer for temporarily accumulating a sedum strip in a sedum slab harvester according to the invention.

In Fig. 1 and Fig. 2 an embodiment of a crop substrate slab harvester, such as a sedum substrate slab harvester, according to the invention is shown diagrammatically in side view and top view respectively. The crop substrate harvester is generally indicated by reference numeral 10 and is mounted to a towing vehicle 12, such as a tractor or other agricultural vehicle. The harvester 10 comprises a frame, shown in a simplified manner by beam 14, provided with one or more wheels 16, which frame 14 carries the various operational units of the harvester 10. In this embodiment the harvester 10 mounted to the vehicle 12, extends at least partially along a lateral side of the vehicle 12. In the situation shown, the vehicle 12 rides in a forward driving direction (indicated by arrow A) on bare ground 18, from which crop substrate 20 comprising reinforcing netting 21 has already been collected. Similarly the supporting wheels 16 ride on the bare ground 18. Thereby damage to the crop substrate 20 to be harvested can be avoided. At the front end of the harvester a guide 22 is provided, which is configured to follow an already cut longitudinal edge 24 (see Fig. 2) of the crop substrate 20 to be collected. The guide 22 comprises for example a proximity sensor or a contact sensor (not shown), a signal of which is processed in a controller 26 which steers the vehicle 12 at a predetermined speed along the field. A first cutting unit 30 comprising two knives 32, e.g. coulter discs, rotatably arranged on a horizontal rotation axis 33 transverse to the driving direction of the harvester, that are configured to cut the longitudinal edges 34 of the strip 36 of crop substrate thus formed in a predetermined width. The front end 38 of the strip 36 is separated from the ground 18 and a separation foil 40, if present, by a separator head 41 , such as an reciprocating (oscillating) plate having a lower plate face essentially parallel to the ground 18, and then taken up by a first conveyor system 42. In the embodiment shown the first conveyor system 42 comprises an endless conveyor belt 43 having multiple, in this case four, endless belts 43’, that are spaced apart arranged parallel to one another, and two rolls 45, at least one of which is driven by a motor (not shown) controlled by the controller 26. Typically in operation the speed of the vehicle 12 and the first conveyor system 42 are maintained at the same speed in order to avoid pull on the strip 36 of crop substrate, which would occur if the first conveyor system speed is higher than the speed of the vehicle 12 and/or to avoid accumulation of the separated strip 36 on the first conveyor system, if the speed thereof would be lower than the speed of the vehicle 12. The crop slab harvester 10 may be provided with a sensor (not shown), e.g. at the guide 22, that measures the (forward) speed of the harvester. The first conveyor system 42 is upwardly inclined with respect to the ground 18, such that the strip 36 is conveyed to a higher level. At the downstream (upper) end of the first conveyor system 42 a second conveyor system 44 is arranged, that is configured for receiving the strip 36 from the first conveyor system 42. At the transfer position from the first conveyor system 42 to the second conveyor system 44 a second cutting unit 46 is positioned, that is configured for cutting a transverse cut in the strip 36 once a sufficient length of strip 36, typically determined by sensors 50, has passed beneath its cutting element. The length may also be determined, based on the known speed of the first conveyor system 42 and/or second conveyor system 44 and the time lapsed after the preceding cut.

An embodiment of a second cutting unit 46 is shown in Fig. 3 and is described in more detail hereinbelow. A slab 48 thus cut from the strip 36 is advanced by the second conveyor system 44. In the embodiment shown the second conveyor system 44 comprises a first subconveyor 44a and a second subconveyor 44b, The second conveyor system 44, in particular the individual speeds of the subconveyors 44a and 44b, is cyclically controlled, such that after the transverse cutting operation of the second cutting unit 46, a spacing between the rear end of the cut slab 48 and the leading end 38 of the strip 36 and thus the leading end of the subsequent slab to be cut, is established. In addition temporarily increasing the speed of the conveyor system 44, e.g. subconveyor 44a, causes the leading end of the strip 36 to be stretched in the forward direction thereby flattening the strip if during the cutting operation of the second cutting unit 46 any hold-up causing wrinkles or folds has occurred. Sensors 50, configured for detecting the presence (e.g. contact switches) and/or position of crop substrate, are typically arranged at the transfer position of the subconveyor 44a to the subconveyor 44b, at the transfer position of the second subconveyor 44b to a stacking unit 52, and at the downstream end of a stacking unit 52, in particular two spaced apart sensors at the downstream end of a stacking conveyor 54 of stacking unit 52. Generally, subconveyors 44a and 44b and stacking conveyor 54 have a similar configuration as the first conveyor belt 43. Thus the conveyors of the crop slab harvester 10 are generally comprised of a plurality of parallel endless belts as illustrated for the first conveyor belt 43. The speed of the stacking conveyor 54 is controlled to be similar to that of the subconveyor 44b upon transfer of a slab 48 from the subconveyor 44b to the stacking conveyor 54. During the stacking operation described below the stacking conveyor 54 is halted.

Foil 40, if present, from which the crop substrate has been removed, will typically have been longitudinally cut into a strip by the knives 32. The embodiment of a harvester 10 as shown in Fig. 1 and 2, comprises a foil collector 60. As shown, the foil strip 40 is wound on a reel 62 contacting the separation foil 40 on the ground 18 and thereby removed therefrom. The outer circumferential surface 64 of the reel 62 will typically have means for taking up the foil 40. Suitable examples thereof comprise a pressure sensitive adhesive, a temporary adhesive, mechanical holding means like pointed projections like needles or other types of projections projecting outwardly from said surface. Once the reel 62 is full with wound foil, it can be removed and substituted by a fresh empty reel. The reel 62 may be driven by free rolling over the ground 18 caused by the forward movement of the harvester 10. Alternatively, the reel 62 may have its own drive (not shown).

An embodiment of a second cutting unit 46 is shown in more detail in Fig. 3. In fig. 3 the second cutting unit 46 comprises a cutter frame 70 mounted on the general frame of the harvester 10. The cutter frame 70 carries a first subframe 72, which on its turn carries a second subframe 73. In this embodiment multiple discs 74 having a diamond cutting edge (not shown) at their circumference are mounted on the subframe 73 adjacent to one another, such that in this embodiment (seen in projection from above) they cover the width of the strip 36. Typically the blades of the discs 74 do not overlap one another in order to make a clean cut in the strip 36 having a reinforcing netting 21. A disc 74 is rotatable about a rotation axis 76 that is arranged parallel to the conveying direction of the strip 36 to be cut. Typically the multiple discs 74 are each synchronously driven by their own drive 75 under control of the controller 26. The subframe 72 is movable, such as slidingly arranged in vertical guides 78, with respect to the fixed frame 70 in the height direction in order to allow free passage of the leading end 38 of the strip 36 underneath the discs 4 by means of a first piston cylinder assembly 76, mounted on rotary axes 77. A second piston cylinder assembly 80, mounted on rotary axes 81 , allows to move, e.g. sliding in horizontal guides 79, the subframe 73 in the transverse direction for providing the transverse cut in the strip 36. During passage of the leading end of the strip 36 below the discs 74 the subframes 72 and 73 return back to its starting position.

The stacking operation is performed on a slab 48, present on the stacking conveyor 54 of stacking unit 52, of which an embodiment is shown in Fig. 4. The stacking unit 52 mounted on the general frame of the crop harvester 10 comprises a stacking unit frame 82, of which two beams 84 (only one visible) extend from the stacking conveyor 54 in a direction transverse to the conveying direction of the stacking conveyor 54. A slab support 86, such as a slab support plate, is movably, for example slidingly, arranged, on the beams 84 between a loading position L and an unloading position U. A first gripper 88 is mounted on the slab support plate 86 and thus movable therewith. The slab support plate 86 extends beneath the upper conveying part of the stacking conveyor in the loading position. At the opposite end of the beams 84 a second gripper 90 is - in this embodiment fixedly - mounted on frame 82. The first gripper is configured for pulling a slab 48 from the stacking conveyor 54 onto the slab support plate 86 by movement of the slab support plate 86. The second gripper 90 is configured for pulling the slab 48 from the slab support plate 86 onto a transport carrier 92 such as a pallet, by return movement of the slag support plate 86. In the embodiment shown, the first gripper 88 comprises a hinged beam 94 driven by a piston cylinder assembly 95, rotatably mounted on rotary axes 97, provided with projections 96. The beam 94 can be rotated about axis 93 between a gripping position as shown in contact with the slab 48 and a non-working position (compare the open position of the second gripper 90) out of engagement with the slab. The second gripper 90 is similarly configured and in the embodiment shown comprises a hinged beam 98 having projections 100, driven by a piston cylinder assembly 99, rotatably mounted on rotary axes 101 and can be rotated between a gripping position in contact with the slab 48 and a non-working position out of contact with the slab. Upon movement of the slab support plate 86 and the first gripper 88 on the beams 84 while engaging a slab 48 on the stacking conveyor 54 and having the projections 96 inserted in the slab 48 to some extent, the first gripper 88 draws the slab 48 from the stacking conveyor 54 onto the slab support plate 86. Thus the slab 48 is conveyed to an unloading (stacking) position lateral from the stacking conveyor 54. Upon arrival at the unloading position the slab 48 is released from the first gripper 88 and the second gripper 90 is actuated to engage the slab 48 on the slab support 86. Upon movement of the slab support 86 back to the position at the stacking conveyor 54 the slab 48 held by the second gripper 90 is slidingly removed from the slab support 86 and positioned on top of any slabs 48 already present on the transport carrier 92. The transport carrier 92 itself is typically supported on a supporting frame 102 of collection carrier 105, of which the supporting arms 104 can be adjusted in height, such that the top of the uppermost slab on the packaging carrier 92 can be set to the height of the slab support 86. The height adjustment may be controlled based on signals of a height sensor configured for determining the height of the top surface. Thereby the transfer of a slab 48 from the stacking conveyor 54 to the packaging carrier 92 is performed, while the slab 48 is supported from below during lateral movement from the loading position at the stacking conveyor 54 to the unloading position at the transport carrier 92.

While the stacking operation has been described with respect to a flat slab, also one or more rolled slabs can be easily, if applicable simultaneously, removed from the stacking conveyor 54 to the transport carrier 92. Rolling of a slab of crop substrate can be performed on the second conveyor system prior to transfer to the stacking conveyor 54, e.g. using a winding device known per se from turf sod harvesters. Such a winding device 106 has been depicted in Fig. 1 in dashed lines.

The crop slab harvester 10 can be provided with a storage 108 (see Fig. 2) for storing a plurality of transport carriers. The storage 108 may have a storage frame 110, configured for carrying a plurality of empty transport carriers 92, which frame is hinged connected to the frame 14 of the crop slab harvester 10 about a vertical axis 112, at the rear (seen in driving direction of the harvester 10) end of the stacking unit 52. If a cut slab 48 does not meet a predetermined length, based on signals from the sensors 50 and/or e.g. the controlled speed of the second conveyor system 44, the slab may be rejected via reject conveyor 114.

In the embodiment shown the second gripper is fixed. If the transport carrier has a surface large enough to collect the slabs in two stacks adjacent to one another, the second carrier can be movably arranged on the beams to a position about half the transport carrier, allowing to stack subsequent slags received on the stacking conveyor on the two stacks in an alternating manner.

Fig. 5 diagrammatically shows an embodiment of a buffer for temporarily accumulating a sedum strip in a sedum slab harvester according to the invention. In Fig. 5 a part of an embodiment of a sedum slab harvester according to the invention is shown, which is provided with a buffer 120 at a position between the first cutting unit 30 and the second cutting unit 46. This buffer 120 buffer is configured for temporarily accumulating the sedum strip 36 that is being passed from the first cutting unit 30 towards the second cutting unit 46. In the embodiment shown the buffer 120 comprises a driven buffer roll 122, over which the strip 36 is guided. Typically the driven buffer roll 122 is positioned at a height in the range of the lower end and upper end of the conveyor 43 of first conveyor system 42. From the buffer roll 122 the strip is guided to the first conveyor system 42 between the conveyor 43 and a freely rotatable guiding roll 124, e.g. mounted with springs to press the strip 36 on the conveying surface of the conveyor 43. An engaging arm 126 is mounted to the second cutting unit 46 at the upstream side thereof, in particular the movable cutting unit subframe 72 that is movable in the height direction. The engaging arm 126 is configured for engaging the strip 36 in front of the cutting elements of the second cutting unit 46 upon performing a cutting operation. The strip 36 and the engaging arm 126 are shown in solid lines during the buffering operation and in broken lines, when the second unit 46 is raised to the position where it does not in contact with the strip 36.

For performing the transverse cutting operation the first conveyor system 42 is temporarily paused, while the driven roll 122 continues to rotate dependent on the speed of the towing vehicle. Simultaneously upon lowering the second cutting unit 46 into contact with the strip 36, the part of the sedum strip 36 in front of the second cutting unit 46 is engaged by the engaging arm 126. During the transverse cutting operation the continuously harvested strip 36 is allowed to sag on both sides of the roll 122, that is to say in this embodiment at the upstream side thereof between the first cutting unit 30 and the roll 122, and at the downstream side between the roll 122 and the first conveyor system 42. Upon lifting the second cutting unit 46 the front end of the strip 36 is released from engagement by the engaging arm 126 and the first conveyor system is again actuated. The extra length of strip derived from sagging during the transverse cutting operation is straightened again by driving the first conveyor system at a slightly higher speed than the towing vehicle.

Claims

1. Slab harvester (10) for harvesting slabs (48) of a crop substrate, such as sedum substrate or sod, from the ground (18), comprising a first cutting unit (30) configured for cutting at least one longitudinal edge (24) of a strip (36) of crop substrate; a second cutting unit (46) configured for providing a transverse cut in the strip (36) of crop substrate, thereby establishing a cut slab (48) of crop substrate from the strip (36) of crop substrate; a separation head (41) configured for separating the strip (36) of crop substrate from the ground (18); a stacking unit (52) configured for stacking cut slabs (48) of crop substrate in a stack arrangement; a conveyor system (42, 44) configured for receiving and conveying the strip (36) of crop substrate and/or cut slabs (48) from the ground (18) to the stacking unit (52); wherein the stacking unit (52) comprises a stacking conveyor (54) configured for receiving a cut slab (48) of crop substrate from the conveyor system (42, 44) and conveying thereof, a collection carrier (105) positioned at a lateral side of the stacking conveyor (54), configured for receiving cut slabs (48) of crop substrate in a stack arrangement; a slab support (86) configured for supporting a slab (48) of crop substrate from below and configured for moving the slab (48) of crop substrate in a direction transverse to the movement direction of the stacking conveyor (54) from a loading position (L) to an unloading position (U), a gripper system (88,90) configured for gripping from above a cut slab (48) from the stacking conveyor (54) and transferring the cut slab (48) onto the slab support (86) in the loading position (L) and configured for transferring the cut slab (48) from the slab support (86) to a collection carrier (105) in an unloading position (U).

2. Slab harvester according to claim 1 , comprising a transfer frame (82) having transfer frame beams (84) extending from the stacking conveyor (54) in a direction transverse to the conveying direction of the stacking conveyor (54), a slab support plate (86) movably supported by the transfer frame beams (84) and configured for reciprocating movement in a direction transverse to conveying direction of the stacking conveyor (54) along the transfer frame beams (84) between the loading position wherein the gripper system (88, 90) slides a cut crop substrate slab (48) from the stacking conveyor (54) onto the slab support plate (86), and an unloading position, wherein the gripper system (88,90) slides the cut crop substrate slab (48) from the slab support plate (86) onto the collection carrier (105).

3. Slab harvester according to claim 1 or claim 2, wherein the gripper system comprises a first gripper (88), preferably mounted on the slab support plate (86), and configured for moving in a direction transverse to the conveying direction of the stacking conveyor (54), and for gripping from above a cut slab (48) from the stacking conveyor (54) and transferring it to the slab support plate (86), a second gripper (90), preferably mounted at a fixed position at the opposite end of the beams (84), configured for gripping from above a cut slab (48) from the slab support (86) and transferring it to the collection carrier (105).

4. Slab harvester according to claim 3, wherein the first gripper (88) comprises an engagement element (94) extending in the conveying direction of the stacking conveyor (54), configured to be movable between an engaging position for engaging the cut slab (48) of crop substrate on the stacking conveyor (54) and an open position.

5. Slab harvester according to claim 3, wherein the second gripper (90) comprises an engagement element (98) extending in the conveying direction of the stacking conveyor (54), configured to be movable between an engaging position for engaging the cut slab (48) of crop substrate on the slab support (86) and an open position.

6. Slab harvester according to any one of the preceding claims 4-5, wherein the face of an engaging element (94, 98) configured for engaging the cut slab (48) is provided with a plurality of projections (96, 100).

7. Slab harvester according to any one of the preceding claims 3-6, wherein the first gripper (88) comprises a first piston cylinder assembly (95) for moving the engagement element (94) between the gripping position and the open position.

8. Slab harvester according to any one of the preceding claims 3-7, wherein the second gripper (90) comprises a second piston cylinder assembly (99) for moving the engagement element (98) between the gripping position and the open position.

9. Slab harvester according to any one of the preceding claims, further comprising a reject conveyor (114) downstream of the stacking conveyor (54), configured for receiving a slab (48) of crop substrate from the stacking unit (52).

10. Slab harvester according to any one of the preceding claims, in particular for harvesting a slab of vulnerable crop substrate such as a sedum substrate, wherein the conveyor system comprises a first conveyor system (42) configured for receiving and conveying a strip (36) of crop substrate separated from the ground (18) by the separation head (41); wherein the second cutting unit (46) is arranged at the downstream end of the first conveyor system (42), a second conveyor system (44) arranged downstream of the second cutting unit (46) and configured for receiving the strip (36) of crop substrate and cut slabs (48) of crop substrate and conveying thereof; wherein the second cutting-unit (46) comprises a cutter frame (70, 72, 73) having a plurality of driven circular cutting elements (74) that are arranged transversely to the conveying direction of the strip (36) of crop substrate and adjacent to one another, and that are configured for movement in a first direction transverse to the conveying direction in cutting contact with the strip (36) of crop substrate, thereby cutting a slab (48) of crop substrate from the strip (36) of crop substrate in the width direction thereof and configured for movement in a second direction, opposite to the first direction, at a height above the first conveyor system (42) and the second conveyor system (44) without contacting the strip (36) of crop substrate.

11. Slab harvester according to claim 10, wherein the plurality of driven circular cutting elements (74) of the second cutting unit (46) are mounted on at least one movable cutting unit subframe (72, 73), that is movably mounted to a fixed cutting unit subframe (70).

12. Slab harvester according to claim 11 , wherein a first movable cutting unit subframe (72) is movably mounted to the fixed cutting unit subframe (70) by a first piston cylinder assembly (76) configured for moving the movable cutting unit subframe (72) in the height direction and a second movable cutting unit subframe (73) is movably mounted to the first subframe (72) by a second piston cylinder assembly (80) configured for moving the movable cutting unit subframe (73) in the first and second direction, wherein the cutting elements (74) are mounted on the second subframe (73).

13. Slab harvester according to any one of the preceding claims 10-12, wherein the circular cutting elements (74) are configured for co-rotation in the first direction.

14. Slab harvester according to any one of the preceding claims 10-13, wherein the driven circular cutting elements (74) are circular blades provided with a diamond cutting edge at the circumference of the blades.

15. Slab harvester according to any one of the preceding claims, further comprising a collector (60), configured for collecting used separation foil (40) from the ground (18).

16. Slab harvester according to claim 15, wherein the collector (6) comprises a rotatably arranged foil winding reel (62) having a rotary axis in the transverse direction with respect to driving direction of the harvester, configured for winding the separation foil (40) from the ground (18).

17. Slab harvester according to any one of the preceding claims, wherein the conveyor system (42; 44) comprises at least two subconveyors (44a, 44b) in series, configured for establishing a spacing between cut slabs (48) of crop substrate from the second cutting unit (46) to the stacking unit (52).

18. Slab harvester according to any one of the preceding claims, further comprising sensors (50), configured for detecting the presence of crop substrate at one or more positions on the first conveyor system (42), second conveyor system (44) and/or stacking conveyor (54).

19. Slab harvester according to claim 18, further comprising a controller (26), configured for controlling the operation of the actively operated harvester components, based on signals received from the sensors (50), preferably also depending on the movement speed of the crop slab harvester (10) over the ground (18).

20. Slab harvester according to claim 19, wherein the controller (26) is configured to drive the first conveyor system (42) at a speed equal to the forward speed of the crop slab harvester over the ground, and to perform a cycle of accelerating and decelerating the subconveyors (44a, 44b) of the second conveyor system (44) in order to create a spacing between cut slabs (48) on the second conveyor system (44).

21. Slab harvester according to claim 19, wherein the controller (26) is configured for determining a slab length from signals received from the sensors (80), and for driving the stacking conveyor (54) and reject conveyor (114), if the determined slab length is outside a predefined range.

22. Slab harvester according to any one of the preceding claims, further comprising a a buffer (120) positioned between the first cutting unit (30) and the second cutting unit (46), which buffer is configured for temporarily accumulating the strip of crop substrate (36) that is being conveyed from the first cutting unit (30) towards the second cutting unit (46).