WO2006094831A1

WO2006094831A1 - Arrangement for drying leafy vegetables

Info

Publication number: WO2006094831A1
Application number: PCT/EP2006/002271
Authority: WO
Inventors: Wilgert Van Och
Original assignee: Sormac Bv
Priority date: 2005-03-10
Filing date: 2006-03-07
Publication date: 2006-09-14
Also published as: NL1028513C2

Abstract

An arrangement for drying washed leafy vegetables such as lettuce, comprising a perforated drum which can be rotationally driven, means for loading the drum with a defined quantity of leafy vegetable and a means for removing the dried leafy vegetable, in which the means for loading the drum comprise a conveyor belt and means for moving the conveyor track between two positions, a first position in which the conveyor belt reaches into the drum and extends over the virtually full length of the drum, and a second position in which the belt is situated fully outside the drum.

Description

ARRANGEMENT FOR DRYING LEAFY VEGETABLES

The present invention relates to an arrangement for drying washed leafy vegetables, such as lettuce, comprising a per- forated drum which can be rotatably driven, means for loading the drum with a certain quantity of a leafy vegetable and means for removing the dried leafy vegetable.

Such an arrangement is known, for instance, from European patent application 1 446 026.

In practice it has turned out that handling leafy vegetables calls great care, because they easily incur damage which leads to a decrease in quality, on one hand owing to the leafy vegetables decaying more rapidly, on the other hand owing to discolorations occurring more easily, causing their merchantability to decrease at a high pace. On the other hand, after washing, it is desired to obtain a given leafy vegetable as quick as feasible in the form of a dry product in order to be able to forward this in the eventual container to the end user as soon as possible. So, forced drying is necessary. In this drying process the leafy vegetables have to be transferred several times from one system to another system, and in practice this is a critical step. In particular, filling a rotary drying drum with leafy vegetables often appears to present problems . Among other things, these problems are caused by the (relative) difference in speed of the leafy vegetables being fed in and that of the drum, which, with a view to gaining time, is often not fully brought to a halt, but is kept rotating at a reduced speed.

The present invention has for its object to provide an arrangement of the type mentioned in the preamble which cir- cumvents the above drawbacks and problems.

This object is reached according to the invention in that the means for loading the drum comprise a conveyor belt and means for moving the conveyor track between two positions, a first position in which the conveyor belt reaches into the drum and extends over virtually the full drum length, and a second position in which the belt is situated fully outside the drum.

By distributing the supply of leafy vegetables over the full length it is achieved that the leafy vegetables have to be moved to a minimum extent when once they have been laid down in the drum so that the risk of being damaged is substantially reduced.

Other features and advantages of the invention will become clear from the following description with reference to the appended drawings. Herein is:

Fig. 1 a schematic side view of an arrangement for drying leafy vegetables or the like according to the invention,

Fig. 2 a top view of the arrangement according to Fig. 1,

Fig. 3 a perspective drawing of the supply section of the arrangement according to Fig. 1,

Figs. 4, 5 and 6 schematic side views corresponding with a part of Fig. 1, in which the feeding belt is depicted in the various positions.

As shown in Figs . 1 and 2 , the arrangement for drying leafy vegetables or the like according to the invention comprises a drying drum installation 1, a supply system 2 for non- dried leafy vegetables and a delivery system 3 for the dried leafy vegetables.

The drying drum installation 1 comprises a frame 10 on which a housing 11 is mounted and in which a drying drum 12 is rotatably supported by bearings. The drying drum 12 can also be suspended in a system of belts as described in European patent application 1 446 026, and can be rota- tionally driven by means of these belts, the driving speed being adjustable in dependence on the type of leafy vegetable to be dried and the stage of processing as will be described hereinafter. The drying drum in itself is known and it comprises a perforated cylindrical drum, the size and number of perforations being chosen in dependence on the nature of the products to be dried and the amount of moisture to be removed.

In the shown embodiment of the invention, the drum is fully open on either end and it is placed at an angle, i.e. the axis is at a small angle of e.g. 15° with the horizontal floor surface, but different [inclination] angles are also suitable and may be used, with the adopted driving method for the drum being adapted, if necessary.

The supply system 2 comprises two belt conveyors 20 and 21, with the belt conveyor 20, as seen from above (in top view) and the axis of drum 12 being in line, and the belt conveyor 21 being perpendicular to the belt conveyor 22, also as seen from above (in top view) . The belt conveyor 21 has an essentially horizontal course and is used for the transfer of the leafy vegetables coming from a washing installation (not described in further detail) , from a position 23 to a position 24 where the leafy vegetables fall on the belt conveyor 20. For this purpose, the position 24 of the belt conveyor 21 is located slightly above the belt conveyor 20.

The belt conveyor 20 is placed on a frame 25 which bears two guide members 26 and 27 through which the actual belt conveyor is supported. Each guide member 26, 27 comprises a first part 28, 29 as shown in Figs. 1 and 3, which extends from the higher part of the drying drum 12 and is virtually parallel to its axis. Via an intermediate part 30, 31, the guide parts 28, 29 are connected with guide parts 32,33 which also extend in a direction essentially parallel to the axis of the drum 12, but, as seen in the vertical plane, they are at an angle with the horizontal floor surface (inclination angle) in opposition to the angle between the axis of the drum and the horizontal floor surface. The ends of the guide members 26 and 27 are connected with the housing 11 so that the supporting part of the supply section 2 comprising the frame 25 and the guide members 26, 27 has a fixed position in relation to the drying drum. Furthermore, the guide members 26,27 are connected with the frame 25 in an appropriate manner.

The belt conveyor 20 in itself comprises an endless belt 35 put round two rollers 36 and 37 which are supported by bearings in two frame plates 38 and 39. The two frame plates are interconnected by^' means of a cross-connection

(not shown) which is inside the belt 35.

Furthermore, in each case, a bracket 40, 41 and a bracket 42, 43 are attached to each frame plate 38, 39. The brackets 40, 41 are mounted at nearly half the distance between the rollers 36, 37, preferably slightly further removed from the drying drum than from the mid-point, and triangular in shape, with near the free end, each time a small guide roller 44, 45 being freely rotatably bearing- supported, such that they can roll along the guide parts 28,29. Because of the position of the small guide rollers 44, 45 in relation to the rollers 36, 37, the belt 35 with the guide rollers 36, 37 will tend to move downward at the end that is situated nearest to the drum 12. To obtain a controlled motion, two brackets 50, 51 are provided on the frame plates 38, 39 near the roller 36, which brackets also are of an essentially triangular shape, with the free end of each bracket each time supporting two rollers 52, 53 in a freely rotatable manner. The two rollers 52, 53 on each bracket 50, 51, as seen in the direction perpendicular to the guide parts 32, 33, are spaced apart such that they grip on the upper respectively lower portion of the guide parts 32, 33. In addition, the rollers 52, 53 may be profiled such that they can not depart sideways from the guide parts 32, 33.

Between the roller 37 and the drum 12 as shown in Fig. 1 there is provided a conveyor belt 60 which is supported by two rollers (not furter indicated) and which is movable in a direction perpendicular to the direction of transport of the conveyor belt 20.

Below the actual belt conveyor 55, i.e. the assembly comprising the belt 35, rollers 36, 37 and the frame plates 38, 39 with additional brackets, a motor 65 connected with a winding arrangement through a clutch (not shown) is pro- vided. One end of a nut 66 is connected with this winding arrangement, which nut - through a freely rotatable guide wheel 67 which is bearing-supported on the connecting piece with the drying drum 1 - returns to a position close to the bracket 41 and is permanently connected. The operation of the feed belt 20 is as follows.

During the drying process of the leafy vegetables or the like, the belt 35 is continuously driven in such a direction that its upper part moves in the direction to the drum. Starting from the position shown in Fig. 1 or 4, leafy vegetable will continuously be carried onto the belt 35 by means of the belt conveyor 21. From this position, the clutch between the motor 65 and the winding arrangement will be engaged, causing the nut 66 to be wound up on the winding arrangement. This results in a movement of the actual belt conveyor 55 in the direction to the drum 12. Consequently, each time a different part of the belt 35 will be filled with vegetable, while at the same time the previously introduced leafy vegetable is transported in the direction to the belt 60. Owing to the motion of the actual belt conveyor, the belt 60 and the adjacent part of the actual belt conveyor 55 will move into the drum, at which time the driving mechanism of the belt 60 starts. The leafy vegetable meanwhile being transferred to it is then brought into the drum 12 at a point where the wall of the drum essentially moves vertically downwards. Owing to the falling motion of the leafy vegetables and the right choice of the drum speed, the leafy vegetable will make a smooth landing on the interior surface of the drum, so to speak.

In addition, the rotational speed of the drum has been chosen such that the leafy vegetable practically does not move in relation to the drum. This is the result of an appropriate gearing to the centrifugal force and the gravitational force, and should also be individually adjusted to each type of leafy vegetable. By means of the shape and direction of the guide parts 32,

33 , 28, 29, the actual belt conveyor 55 is moved further and further into the drum, with the plane of the upper part of the belt 35 coming gradually into a position more paral- IeI to the axis of the drum 12. During this continued motion, more and more leafy vegetable is fed to the drum until virtually all the interior surface of the drum is covered with leafy vegetable.

At that moment the actual belt conveyor has reached its final position within the drum and the engagement of the clutch between the motor 65 and the winding arrangement is interrupted. A second driving mechanism possibly connected with the motor 65 through a clutch is started, causing the actual belt conveyor to move in the reverse direction. During this return motion the belt is still being loaded, but, any leafy vegetable is no longer carried into the drum 12 , owing to an appropriate choice of the speed of the belt 35 and the speed of the return stroke.

Just after the start of the return stroke, the driving mechanism of the belt 60 is halted, so the belt is entirely empty, and the rotational speed of the drum 12 is increased to a level at which the liquid is separated from the leafy vegetables by means of centrifugal force and is discharged through the openings in the drum.

At the time that the return motion of the actual belt conveyor 55 has almost been ended, i.e. just before the posi- tion of Pig. 4 is reached again, the speed of the drum 12 is reduced to a level at which the leafy vegetable fall from the drum 22 to the belt conveyor 3 due to the gravitational force. The delivery of the leafy vegetable from the drum is practically ended at the moment that the actual belt conveyor 55 reaches the position shown in Fig. 4. At that time, the upper part of the belt 35 is largely filled with a layer of leafy vegetable and the return motion of the actual belt conveyor 55 is stopped and, reversely, changed into a feed motion as described above.

It is obvious that owing to an appropriate choice of the speeds of the belt 35, and the speeds of the alternate motion of the actual belt conveyor 55 and of the belt conveyor 21, too, a virtually uninterrupted process is obtained, notwithstanding the fact that actual drying is batch by batch.

The resemblance to a continuous process is still enhanced by the fact that the delivery system 3 comprises an endless conveyor belt which can be driven at two different speeds . When emptying the drum onto the belt of the delivery system 3, the belt is driven at a high speed in such a way that, when the drum 12 is completely empty, the upper part of the belt is practically completely filled with leafy vegetable. Subsequently, the belt of the delivery system 3 is driven at a low speed, in such a way that the belt gradually delivers the leafy vegetable to a further process station, for example, a packaging arrangement. Through a suitable setting of the various cycles of the supply section 2, the drying time in the drying arrangement 1 and the delivery section 3 it can be achieved that on one hand the leafy vegetable is practically continuously supplied and delivered, whereas in the drum 12 a batch process is running, entailing a much lower risk of damaging the leafy vegetables. By doing so, it is also reached that a preceding [and/] or following processing station can continuously operate in processing. It will be understood that the invention is not limited to the embodiment described and illustrated, but that within the scope of the claims numerous alterations can be made.

Claims

1. An arrangement for drying washed leafy vegetables such as lettuce, comprising a perforated drum which can be rotationally driven, means for loading the drum with a defined quantity of leafy vegetables and a means for delivering the dried leafy vegetables, characterized in that the means for loading the drum comprise a conveyor belt and means for moving the conveyor track between two positions, a first position where the conveyor belt reaches into the drum and extends over virtually the full drum length, and a second position where the belt is situated fully outside the drum.

2. The arrangement according to claim 1, characterized in that in front of the end of the conveyor belt which in the second position faces the drum there is provided a small cross-conveyor belt through which the leafy vegetable can be transported in a direction perpendicular to the direction of transport by the conveyor belt.

3. The arrangement according to claim 2, characterized in that the delivery end of the small cross-conveyor belt is situated at a level where the drum moves virtually vertically downwards.

4. A method for drying leafy vegetables such as lettuce, by which the leafy vegetable is dried in a perforated drum by means of centrifugal force, by which the leafy vegetable is supplied by means of a feed belt which is provided on one end of the drum and which as a whole can be moved into and from the drum, by which the leafy vegetable is loaded into the drum during the motion of the feed belt, characterized in that the drum during loading is driven at a first relatively low speed, the speed being sufficient to hold the leafy vegetables in position against the drum wall and in that, during drying, the drum is driven at a higher speed at which an effective separation of water and leafy vegetable takes place.

5. The method according to claim 4 by which the drum is positioned at an angle with the horizontal plane and the speeds are chosen accordingly.

6. The method according to claim 5, characterized in that the drum can be driven at a third speed by which the leafy vegetable falls from the drum.