The finishing department, covers the area from the discharge of the main drag belt (at the top), through the top fans, the leaf sorting belt, the mini-shakers, down the discharge chute and the tables.
All of these processes have related functions, not the least being the bottom fans, drag belt speed, and ground speed.
I have discussed the top fans before. Essentially they operate at a very delicate moment – that is when the fruit and juice is transferred to the leaf sorting belt – as it is being catapulted off the belt and free-falls onto the leaf sorting belt.
As it travels over this gap between these two processes, the top fan pressure determines exactly how much of the MOG is removed – including also how much juice and grape berry is removed. If this setting is not 80-90% of the top fans, or is simply just too high, the discharge duct from the fans will be awash with juice and MOG and will be making a considerable mess.
Once the matter is on the leaf sorting belt (in conveyor technology terms it is just a transfer belt), individual berries and juice drops through this belt onto the discharge tray, which drops it all through the rollers and into the bin. Bunches are transferred through a second set of shakers (much smaller and much faster), where the berries and juice drops through, while remaining MOG runs off the end of the belt onto the discharge tray.
All fruit, juice and MOG land on the tables (rollers) and drops through into the collection bins, where (hopefully) all MOG and petioles are run off the side of the sorting tables and drop onto the ground.
If you ever get a chance, get up on top of the harvester whilst it is working, and open the top hatch where the fruit is thrown off the drag belt and onto the leaf sorting belt. It comes off at such a speed that fruit can fly out above the hatch onto the top of the top fan casing. The drag belt is going through a 180-degree turn – it isn’t any wonder the driver can lose a lot of fruit at the bottom fans area, where the drag belt goes through a similar movement.
At this point, the fruit, juice and MOG is mid-air and with the covers closed, the fan can lift out more than just leaf, but juice as well. A dead giveaway for this is taking note of the amount of juice discharging from the exhaust ducts at the back. If they are excessively wet and running with juice, you know the fans are too high.
Fruit and juice then falls through the leaf sorting belt, runs down the discharge chute onto the sorting tables.
Fruit bunches and MOG is unable to fall through the leaf sorting belt, and so travels along the belt through a mini-shaker. This is a similar but much smaller shaker unit to the main shakers but one the operates at twice the rate, anywhere from 750c/min to 1200c/min. These shakers, or destemmers, sit very close to the top of the leaf sorting belt, and are much closer together so any bunches that are still present and shaken violently and the juice and fruit is removed, and drops through.
The mini-shaker frequency is determined by none other than watching the rear of the discharge tray for any fruit still attached to the rachis (some call it the wrack). The correct setting will result in a pile of empty rachis crossing the sorting table which is dumped on the ground, easily found when the harvester has stopped as the driver conducts his visual check of the vine in the first row. If the rachis is broken, then it is generally viewed that the setting is too high. Exact guidelines are 1-2 rachis with 3-4 berries remaining per bay (vine panel) is a good setting.
The sorting tables sit above the collection bins and are shaped appropriately to perform two roles. The first set of rollers the fruit and MOG comes in contact with allows for the passing of juice but their main role is to re-align MOG and trash such as petioles perpendicular to themselves. Once this is done, they tend to run off the side of the second set of rollers, whereas the fruit drops through and into the collection bins.
Generally speaking, the tables are run at the maximum speed possible, backed off slightly to ensure fruit is covering the rollers evenly, but 1 or 2 rollers back from the outside edge.
Whether the mini shakers cycle setting is set high enough or not, is determined by how much fruit is still on the rachis when they drop off the side. The best time to note this is when the machine has stopped whilst in it’s first setup row, or when it slows down once coming out of the row to turn around. Additionally, what you also do not want to see is wads of leaf and juice running off the side as well. This is the telltale sign of the fans set too low, and the mini shakers pack leaf and juice together in a pancake. One can also take a ride on the harvester, to view the discharge tray and note the quantity of trash collecting and running across the rollers.
Remember? Ground speed is practically related to everything that could be wrong.
The leaf sorting belt speed is proportional to the main drag belt speed, which is determined by ground speed. If you think something is wrong, first thing is to slow down which makes the whole process more manageable.
Other features include a magnetised discharge tray. The winemaker should demand this is present, as this removes all metal manner from entering the bins (nails, staples and so on). A bin level indicator is available on some models and as an add-on. This too should be demanded by the vineyard owner, to ensure driver forgetfulness does not allow fruit or juice to overflow the bin.