WO1990000714A1

WO1990000714A1 - Quasi-continuous drying of small-sized, washed lettuce, vegetables and fruit

Info

Publication number: WO1990000714A1
Application number: PCT/CH1989/000049
Authority: WO
Inventors: Hans Kessler
Original assignee: Ultra Maschinenbau, H. Kessler & Co.
Priority date: 1988-07-13
Filing date: 1989-03-16
Publication date: 1990-01-25
Also published as: AU3204289A; CH675345A5; EP0380595A1

Abstract

Cut, mixed vegetables or lettuce in particular are dried in a device having a controllably driven centrifugal basket (20) with an inner envelope (72) shaped as a perforated plate (70) or sieve. The centrifugal basket (20) open at its two extremities works alternatively during a first period at a higher speed of rotation and during a second period at a lower speed of rotation. The washed, wet goods (48) are introduced at least during the second period into the centrifugal basket through its top opening (50), pass therethrough quasi-continuously and leave it as dried goods (56) through its bottom opening (54) during the second period. During the first period, the goods adhere under the influence of the centrifugal force to the inner envelope (72) of the centrifugal basket (20). During the second period, they loosen themselves from the upper part of the inner envelope (72) fall into its lower part where they are once again entrained and moved forward by a certain distance. The centrifugal basket (20) has completely open frontal faces (50, 54) at both its extremities. The bearing sections of the basket are designed in such a way that the perforated plate (70) or sieve is stiff enough and that it is possible to perfectly wash out the basket.

Description

Quasi-continuous drying of washed, small-sized salads, vegetables and fruits

The invention relates to a method for drying washed, small-sized vegetables, salads and fruits, in particular sliced mixed vegetables or mixed salads, in a controllably driven centrifugal drum inclined with respect to the horizontal with an inner jacket designed as a perforated plate or sieve. The invention further relates to a device for carrying out the method.

In packaging plants, for example for lettuce, several hundred kilograms of at least partially cut or grated goods are washed per hour and then packaged in portions in plastic bags. Partial cut ge mixed salad, for example, is packaged athylenbeutel g usually in the poly ^'to 250th

For reasons of quality, the goods must be dried after washing, for which the centrifugal centrifuge process is best suited for small-sized goods.

According to conventional methods, the washed goods are poured in portions of 5-8 kg into stainless cylindrical baskets, which can be made from a perforated plate. The baskets are then placed in a swing arm with a vertical axis of rotation and this is switched on. The speed or frequency is relatively high, it is usually around 900 to 1200 revolutions / minute. It usually takes 2 to 3 minutes until a basket with dried goods can be removed and replaced with a new one filled with moist goods. It can be found that this takes a long time with a high one The working process speeds the material remaining near the axis of rotation dried less well than the peripheral.

CH-A5 660 670 describes a device for the automatic spin-drying of washed, small-sized vegetables and salads, and a method for operating the device. This device essentially consists of at least one centrifuge with a strainer basket, a feed device to / from the centrifuge (s) and a discharge device. The axis of the centrifuge (s) is / are inclined so that the opening of the strainer basket is directed downward. The discharge end of the almost horizontal feed device can be pushed into the sieve basket.

In a periodic cycle, the lettuce is dropped into the rotating sieve basket in portions and swung out. At a low speed of the sieve basket, the dried lettuce is ejected through the opening of the sieve basket and reaches the packaging via the cross conveyor belt! age.

The inventor has set himself the task of creating a method for drying washed vegetables, salads and fruits of the type mentioned at the outset, as well as an apparatus for carrying out the method, which have the performance without impairing the gentle treatment and without production of increasing losses.

With regard to the method, the object is achieved according to the invention in that a centrifugal drum which is open on both sides operates alternately during a first period at a higher speed and during a second period at a lower speed, the washed, moist material at least during the second period of time is passed through the upper opening into the centrifugal drum, passes through it practically continuously and during the second period it emerges as a dry material from its lower opening, the material being affected during the first period The centrifugal force adheres to the inner casing of the centrifugal drum, but during the second periods in the approximately uppermost position it detaches from the inner casing, falls into its lower region and is carried there again with a certain feed.

The method according to the invention differs significantly from the known state of the art in that the work is quasi-continuous, which is only possible if the material to be dried does not emerge on the filling side of the centrifugal drum.

During the filling process, the washed, small-sized material falls from a feed device through the upper opening of the centrifugal drum onto its inner jacket. There, the material is gripped, accelerated and rotated by the rotating centrifugal drum.

During the first period with the centrifugal drum rotating at a higher speed, the centrifugal force in each position is greater than the gravitational force, the moist material rotates with the centrifugal drum and is dried. However, the speed must not be so high that the goods are damaged, in particular lettuce must not be squeezed.

During the second period with the centrifugal drum rotating at a lower speed, the centrifugal force becomes smaller; shortly before reaching the uppermost layer, the gravitational force acting on the material becomes greater than the centrifugal force acting counter to it here. In this area, the material detaches from the inner jacket of the centrifugal drum and falls down. There the goods are grasped again, accelerated, lifted, detached again in the uppermost position and fall again downwards. The newly filled, moist material also behaves in the same way. In practice, the first period is preferably two to six times as long as the second period. The higher speed used in the first period preferably reaches four to ten times the value of the lower speed. Thanks to the quasi-continuous process, the higher speed of the centrifugal drum during which the washing water is removed can be operated at a speed of preferably only 200-400 per minute, for example during 8 to 12 seconds. 40-50 revolutions / minute have proven to be expedient for the lower rotational speed, while the material in the approximately uppermost position can detach itself from the inner casing of the centrifugal drum. In practice, about 2 - 4 see are sufficient to use the lower frequency. However, these quantitative values are strongly dependent on the material to be dried, the size and shape of which depend. In the case of material not yet tested in centrifugal drums other than those previously produced, values other than those specified above can be advantageous.

The material can detach from the inner jacket of the centrifugal drum during two to three revolutions and fall downward. This results in a gradual feed in the longitudinal direction of the centrifugal drum, which is particularly dependent on the fall distance and the angle of inclination of the centrifugal drum with respect to the horizontal. Furthermore, during the flight phase of the second period, the good changes its position, it is shifted, leaves are turned.

Accelerating or braking the centrifugal drum preferably does not take longer than a second period at the lower speed, that is to say about 2-4 seconds. The transition from the higher to the lower speed and vice versa is smooth. The above-mentioned detachment of the material from the inner casing of the centrifugal drum takes place towards the end of the abrasion and continues during the beginning of the acceleration. During the passage through the centrifugal drum, the material is preferably accelerated to drying about five to ten times and then slowed down to a gradual advance, corresponding to 5-10 working cycles.

The washed, moist material can only be filled in at the lower rotational speed of the centrifugal drum during the second period, with the filling already starting at the end of braking and / or being able to be stopped only after acceleration has started. It is also possible to operate the feed device continuously, as a result of which continuously washed, moist material falls into the centrifugal drum. Goods distributed irregularly during the first periods are balanced out during the flight phase of the second period.

With regard to the device for carrying out the method, the object is achieved according to the invention in that the centrifugal drum has completely open ends on both sides, a feed device opens into the higher opening on the front side of the centrifugal drum, and a discharge device below the Another, lower-lying opening of the centrifugal drum is arranged, and the drive means of the centrifugal drum, the feed and the discharge device are connected to a central control system.

The centrifugal drum preferably has a shaft with support tubes cantilevering at regular intervals with respect to the longitudinal axis. These are each offset by a constant angle, for example 60 ', 72 ^* , 90 ^* or, which is particularly expedient, by 120 ". The offset angle can be easily observed in the axial direction of the centrifugal drum. Depending on the offset angle, six (60 '), five (72 ^* ), four (90 ^* ) or three (120 ^* ) longitudinal T-profiles connected to the relevant ends of the support tubes. The first support tube can be arranged indented on at least one end face of the centrifugal drum, the distance of this first support tube from the end face preferably being the same as that to the next inner support tube.

According to a variant, the centrifugal drum can also be agitated on the outside.

The invention offers the following advantages:

The quasi-continuous centrifugal drum, which is open on both sides, has a significantly higher performance than previously known devices. The throughput is so high that only one centrifugal drum has to be used per feeding device. As a result, there is no waste due to the switching of the feed device.

The washed items are treated more gently because the spin speed is lower. This is possible because the material is turned several times at lower speed in the flight phase of the second period.

The throughput and the performance of the centrifugal drum are essentially determined by the following factors:

Inclination of the centrifugal drum. The incremental feed is directly dependent on the angle of inclination. Inner diameter of the centrifugal drum. With a larger diameter, the fall distance and thus a feed stage is larger.

Higher speed range. The faster the centrifugal drum rotates, the faster the wash water is removed. However, careful treatment is important. - Lower speed range. The later the material detaches from the inner jacket of the centrifugal drum, the greater the fall distance and thus also the feed stage. Length of the centrifugal drum. The longer the centrifugal drum, the more working cycles are possible. First period. The longer the material is spun at high speed, the more wash water is removed per work cycle.

Second period. The longer the lower speed is used, the greater the feed per treatment cycle. - Surface condition of the inner jacket. This influences the distribution of the goods.

The various parameters can be optimally combined with one another, depending on the material to be dried. Some parameters cannot be changed in normal operation (length and inside diameter of the centrifugal drum, surface quality of the inner jacket), the inclination of the centrifugal drum - if it can be adjusted manually - can be changed with some effort, other parameters can be controlled automatically ( Speed, first and second period, machine-adjustable inclination).

The invention is explained in more detail with reference to the exemplary embodiments shown in the drawing. Schematic diagrams show:

1 is a partially cutaway view of a quasi-continuous device for drying washed, small-sized salads, vegetables and fruits, FIG. 2 is a side view of FIG. 1,

3 shows a view of a centrifugal drum in the axial direction, with the jacket removed, FIG. 4 shows a side view of FIG. 3, FIG. 5 shows a perforated plate for forming the jacket of the centrifugal drum, and

6 shows a detail B from FIG. 3. In a firmly anchored frame 10 with cross struts 12 and side struts 14, a support frame 18 for a centrifugal drum 20 is pivoted about an axis of rotation 16. The support frame 18 is fixed by means of screws, not shown, which are guided through slots 22 crossing at right angles. A total of three pairs of intersecting slots 22 are provided in corresponding plates 24. Before the screws are tightened, the angle of inclination 0t of the shaft 26 of the centrifugal drum mounted in the pivotable support frame 18 can be set by means of a spindle 28. In the present example, the angle 0 with respect to the horizontal is set between about 7.5 and 15 ^* Ibar.

The centrifugal drum 20 is covered by a hood 30 which can be easily lifted off. This is essential for cleaning the centrifugal drum 20. The hood 30 also covers the upper half of the end openings 50, 54 of the centrifugal drum 20. On the filler side, it can be lifted off or made transparent for control purposes.

An electric motor 32, arranged in a housing 34, serves to drive the centrifugal drum 20. The drive takes place via drive wheels 36, 38 by means of V-belts 40. The electric motor 32 flanged to the pivotable support frame 18 is displaceable vertically to the axis A of the centrifugal drum 20.

Instead of the electric motor 32, another controllable drive element can be used, for example a hydraulic or pneumatic drive motor with a control program.

The means for controlling the electric motor 32 are omitted for the sake of clarity. Common means are used in control and computer technology. The washed material 48 thrown into the centrifugal drum 20 in the direction of the arrow 44 by means of a feed device 46 designed as a conveyor belt comes into contact with the inner jacket 72 (FIGS. 5, 6) of the centrifugal drum in the region of the upper end face 50 taken along. In a quasi-continuous process, the washed, initially moist material 48 passes through the centrifugal drum 20 in the direction of arrow 52 and finally emerges from the lower opening 54 of the centrifugal drum as dried material 56. The dried material 56 falls onto the discharge device 58, which is also designed as a conveyor belt and runs in the transverse direction, and can be guided to downstream packaging units.

According to a variant (not shown), a direct drive of the centrifugal drum 20 is provided, in that the drive unit is mounted coaxially with the axis A. This embodiment, which is simplified at first glance, is somewhat bulky and cumbersome.

3 shows a centrifugal drum 20 which can be rotated about an axis A by means of its tubular shaft 26 in detail. On both sides of the shaft 26 shaft journals 60 are inserted into the tube, which are used for storage. The longer shaft journal 60 has a gradation on the face side, which ent the drive wheel 38 (FIGS. 1, 2) as drive shaft 62 di.

Radial support tubes 64 protrude from the shaft 26 at right angles, which are arranged offset in the longitudinal direction A at regular intervals by a regular angle, here by 120 ^* . On both ends of the centrifugal drum 20, the first support tube 64 is arranged inwardly. At the front ends of the support tubes 64 lying one behind the other in the direction of the longitudinal axis A, a longitudinally running profile 66 with a T-shaped cross section is attached, ie a total of three. The offset by 120 ^{* of} the support tubes 64 can be seen better in FIG. 4, likewise the shape of the three longitudinal T-profiles 66.

On the three T-profiles 66, three reinforcement rings 68 are attached, which are square tubes in the present case. These prevent the centrifugal drum 20 from deforming at high frequencies.

Perforated plates 70 (FIG. 5) are attached to the longitudinal T-profiles 66. These perforated plates 70, one each of which covers one third of the circumference of the centrifugal drum, form the inner casing 72 connected to one another in the longitudinal direction, connected to one another, with holes 74 for the washing water to escape from the centrifugal drum 20.

In each case in the extension line of a support tube 64, the perforated plate 70 opposite with respect to the longitudinal axis A is connected to the reinforcing ring 68 by means of a flat steel 76. As shown in FIG. 3, this flat steel 76 can be limited only to the area of the reinforcement ring. However, it can also extend over the entire length of the centrifugal drum 20, but this also results in mass to be accelerated and braked.

6 shows, in the viewing direction of the longitudinal axis A of the centrifugal drum 20 (FIG. 4), the fastening of perforated plates 70 and a reinforcing ring 68 to a support tube 64 via a longitudinal T-profile 66. This T-profile 66 is connected to the Support tube 64 welded. The perforated plates 70 are welded to the short legs of the T-profile 66, the reinforcement ring 68 to its long legs. The distance d of the perforated plate 70 from the reinforcing ring 68 allows continuous cleaning, which is very important for hygienic reasons. The centrifugal drum 20 shown as an exemplary embodiment in FIGS. 3 and 4 has a length of 150 cm and an inner diameter of 80 cm. All components of this centrifugal drum are preferably made of stainless steel, especially chrome steel.

The load-bearing profiles of the centrifugal drum are designed in such a way that there is sufficient rigidity and at the same time there is the possibility of rinsing the drum properly with simple means and little effort.

Claims

1. Method for drying washed, small-sized vegetables, salads and fruits, in particular cut ^' mixed vegetables or mixed salads, in a controllably driven centrifugal drum (20) inclined with respect to the horizontal with a perforated plate (70) or sieve-formed inner jacket (72),

characterized in that

a centrifugal drum (20), open on both sides, operates alternately during a first period at a higher speed and during a second period at a lower speed, the washed, moist material (48) at least during the second time periods through the upper opening (50) is guided into the centrifugal drum, passes through it virtually continuously and emerges as dry material (56) from its lower opening (54) during the second periods, the material during the first periods under the action of centrifugal force on the inner jacket (72 ) the centrifugal drum (20) adheres, but during the second periods, in the approximately uppermost position, it detaches from the inner jacket (72), in the lower region of which falls and is carried there again with a certain advance.

2. The method according to claim 1, characterized in that the first period with a higher rotational speed of the centrifugal drum (20) is 2-6 times as long as the second period with a lower rotational speed, and the higher rotational speed is preferably 4- Is 10 times greater than the lower speed.

3. The method according to claim 1 or 2, characterized gekennzeich¬ net that the centrifugal drum (20) during a first Period of B - 12 _ec runs at a speed of preferably 200 - 400 per minute and a second period lasts 2 - 4 seconds.

4. The method according to any one of claims 1-3, characterized ge indicates that the acceleration or braking of the centrifugal drum (20) lasts at most as long as a second period at the lower speed.

5. Apparatus for performing the method according to one of claims 1-4,

characterized in that

the centrifugal drum (20) has completely open end faces (50, 54) on both sides, a feed device (46) into which a higher front opening (50) of the centrifugal drum (20) opens, a discharge device (58) below the other, lower one the opening (54) of the centrifugal drum (20) is arranged, and the drive means of the centrifugal drum (20), the feed device (46) and the discharge device (58) are connected to a central control system.

6. The device according to claim 5, characterized in that the angle of inclination [~ L) of the centrifugal drum (20) with respect to the horizontal is about 7.5 - 15 ^* .

7. The device according to claim 5 or 6, characterized gekennzeich¬ net that the centrifugal drum (20) has a tubular shaft (26), of which in the axial direction (A) arranged at regular intervals, extending in the radial direction, each by one Cantilever regular support tubes (64) for holding the inner jacket (72), the offset preferably being 120 ^* .

8. The device according to claim 7, characterized in that the first support tube (64) on at least one end face of the centrifugal drum (20) is moved inwards.

9. The device according to claim 7 or 8, characterized gekennzeich¬ net that in the longitudinal direction (A) of the centrifugal drum (20) extending T-profiles (66) are connected to the corresponding Stütz¬ tubes (64), which T-profiles on the one hand Fastening of the wire or perforated plate segments (70) forming the inner jacket (72) and, on the other hand, serve for fastening reinforcing rings (68) surrounding the centrifugal drum (20) at a distance (d).

10. The device according to claim 5 or 6, characterized gekennzeich¬ net that the centrifugal drum (20) is agitated outside.