The present invention relates to a method and an apparatus for cleaning objects stacked in the manner of a stack, for example trays, more particularly trays for eggs or food products as fruit or vegetables, the apparatus comprising at least a cleaning unit with basin with cleaning liquid for cleaning the trays.

Methods and apparatus for cleaning trays of the type as mentioned above (for example nestable trays, for example egg trays), made of a suitable plastic, are generally known.

A recent example thereof is described in CN108067487. The successive steps, which include the separating of these trays, are mentioned in detail.

Another example is shown in US2013092187, in which an apparatus is shown for cleaning plastic boxes or small boxes, initially stacked into each other (nested), and then, one by one, taken off the stack from above, and thereafter, inverted, fed to an apparatus for cleaning them.

In SU902880, a stack of plates is cleaned after first having been placed, centered, on a central support in a rack with support edges for each plate separately, after which cleaning liquid is guided trough the interspace.

Of applicant, an apparatus is known, with designation CTW3250 and CTW6500 (see www.moba.net under tray washer), in which stacks of nested trays are supplied, whereupon the trays are singulated in the usual manner with denesters, then, in a washing tunnel, irrigated with cleaning liquid, and brushed.

The above-mentioned methods, however, are deficient in particular when high processing capacities are required, more specifically when series of stacks are to be processed.

To remedy this deficiency, the method according to the invention provides a method which comprises dropping a stack of objects to be cleaned (for example a stack of nested trays) into a cleaning liquid. According to an aspect of the invention, the stack is released above the cleaning liquid so as to make a (brief) falling motion.

During or under the influence of that falling motion (also: movement), the objects can briefly come loose from each other, and land in the cleaning liquid as a stack (to nest again directly). It is then additionally advantageous when the stack as a result of the fall is completely immersed in the cleaning liquid. After falling (and impact in the liquid), the stack can remain intact, for example when the stack of objects retains a nested condition.

In particular, the method comprises one or more of the following steps:

- providing a stack of objects, for example by placing objects stacked into each other (for example nested, nestable objects) on a support element,

- setting the stack (briefly) in (falling) motion, whereby the objects stacked into each other can accordingly (briefly) come loose from each other, and

- passing this stack through a cleaning liquid, in particular after said setting the stack in motion.

It has been found that as a result of the motion (preferably a falling motion), not only can the stacked objects come loose from each other but also dirt comes loose from these objects, which is a highly advantageous and quick result in this field of automation.

The stack may be discharged in an advantageous manner, by transporting the stack being in the liquid by means of a conveyor extending above the stack (set up above or in the basin). The stack may for instance under the influence of an upward force be pressed against a transport side of the conveyor facing the stack. This applies in particular if the objects concerned have a lower density than a density of the cleaning liquid.

Furthermore, the present invention provides an apparatus, comprising, - supply conveyor for feeding a stack of at least two trays to a device for bringing the trays into contact with a cleaning liquid,

- a cleaning unit with basin with cleaning liquid which the trays are brought into contact with,

- discharge conveyor for passing the trays out of the cleaning unit, wherein the cleaning unit furthermore comprises a drop tower for guiding the trays substantially vertically from the supply conveyor to and dropping the trays into the basin placed thereunder.

It has been found that by setting the stack or also a single tray briefly in motion, the trays come loose from each other and dirt residues come off. More particularly, this means for a stack that laborious destacking and loosening operations, to be carried out by corresponding complex mechanical systems, can be omitted. It has been found that with great advantage processing time has thereby been shortened considerably and also that in this way production costs can be saved on.

Apparatus for loosening dirt residues on objects by setting these objects briefly in motion is known, for example from:

DE2549551 in which it is described how a piston-hammer system, placed on an object to be cleaned, can loosen such residues by hammering, and

EP1442999 in which a particular piston system for a

piston-hammer system as just mentioned is shown.

The hammering that is used in these systems is not suitable for the type of objects such as trays which will get damaged upon such impulse transfer. Nor is the use of cleaning liquid mentioned.

More particularly, in the present invention it has been chosen to set in motion the objects themselves, namely the stack of trays here, more specifically, to have them move in a drop tower and fall along a well-defined trajectory whereafter the stack to be cleaned ends up in a basin. It is known from GB2156326 for trays to be brought from a lower end of a stack, one by one, through a circular downwardly running channel, into a vertical position and then to be dipped in a liquid, but this movement, not carried out until after coming loose, only serves the purpose of bringing such a tray in a suitable cleaning position.

Further, the invention provides a method and an apparatus for displacing objects which are to be cleaned through a basin with liquid, in particular cleaning liquid. To this end, the apparatus comprises a washing conveyor.

Further, extra advantageous elaborations of the invention are described in the subclaims.

Further features and details of the method and apparatus according to the present invention will be explained in detail hereinafter on the basis of a drawing, in which,

FIGURE 1 shows an exemplary embodiment of a drop tower, and

FIGURE 2 represents an example of a system in which the drop tower is applied.

FIGURES 1-2 show a non-limiting example of an apparatus for cleaning objects, for example trays T, more particularly trays for eggs or food products as fruits or vegetables.

The apparatus comprises a supply conveyor 2 for feeding stacks of objects (i.e., stacked objects) T. Such a supply conveyor 2 may be

implemented in different manners (for example, comprising a conveyor belt, roller conveyor, robotic gripper conveyor or the like).

Further, the apparatus comprises a cleaning unit 8 with basin 9 with cleaning liquid 10 (which the trays are brought into contact with during use).

Preferably, the apparatus comprises a discharge conveyor 11 for passing a stack of objects as mentioned (preferably in stacked condition) out of the cleaning unit. Means 1 are provided for dropping a stack of objects T supplied by the supply conveyor 2. These drop means comprise a drop tower 1. The present drop tower 1 extends from and/or above the basin 9. The present drop tower 1 is configured for dropping the objects substantially vertically, into the basin 9. Thus, each stack of objects can be briefly set in (falling) motion, to be caught in the cleaning liquid in the basin 9.

In FIGURE 1 there are shown, in particular, in isometric view:

- a drop tower 1 as mentioned, with a housing which in this FIGURE 1 comprises corner posts 5a, 5b, 5c, and furthermore side

plates 6a, 6b;

- a supply conveyor 2 (schematically shown) which is configured to supply a stack of trays 3 to the drop tower 1 in supply direction T, for instance such that the supplied stack 3 is positioned at the top within the housing of the drop tower 1 on at least two support edges 4a, 4b. These support edges 4a, 4b can be swung clear from a stack- supporting position, so as to have the stack 3 fall. In this example, this fall is guided by the represented plates 6a, 6b and posts 5a, 5b, 5c (of the drop tower). It will be clear that a stack 3 may also, without such supporting edges, be released directly, by the supply conveyor 2, into the drop tower 1 to make a falling motion as mentioned. It is preferred, however, to hold the stack 3 initially in stacked condition at the top above (in) the drop tower 1 and then to release the stack (as by means of the swing-clear support edges 4a, 4b) so that the stack accelerates downwards (falls) in a stacked condition.

The drop tower 1 further comprises support plates 7 which rest on the bottom of the basin 9 (see FIG. 2).

A direction of fall of the stack is schematically indicated with arrow C in FIGURE 2. As follows from the drawing, during use a liquid level in the basin 9 is preferably so high (and the basin is deep enough) that the stack 3 falling into the basin 9 can be completely immersed in the liquid (with immersion taking place in particular under the influence of gravity and the falling motion).

To a person skilled in the art it will be clear that as soon as the (falling) stack 3 reaches the liquid surface in the basin 9, a shock passes through this stack 3 whereby in general all trays placed into each other (in particular nested) come loose from each other for just a moment (then to nest again) and furthermore dirt residues on these trays, or at least parts of these dirt residues, come off the trays. Thus, a particularly efficient cleaning of the stacks 3 can be achieved.

Most clearly, in FIGURE 1 a non-limiting example of an

embodiment of the invention is shown. The drop tower may be implemented in different manners. Depending on preferences and requirements, corner posts and walls (of such a stack drop tower 1) can be changed and adapted, or also other guides may be employed for such a fall. In such a working environment, in general, machine parts that can be hosed down will be used, namely of suitable plastics or stainless steel. The conveyors used will conventionally be endless in most cases.

In FIGURE 2, in side view, there is shown schematically (cut-away) a cleaning unit 8 in which the drop tower 1 is used. Such a cleaning unit or system 8 is often referred to as washer.

Indicated on the left in this FIGURE 2, in the drop tower 1, is an arrow C (chute) for the direction in which, during use, the stack 3 moves down and falls, and thus ends up in a basin 9 with liquid 10. In the exemplary embodiment represented here, the liquid 10 has a density which is greater than that of the objects to be cleaned, for example the trays (of stack 3).

The exemplary embodiment comprises a washing conveyor 11. In this example, the washing conveyor is configured to engage a stack of objects being under it (in the washing liquid). The washing conveyor 11 may for instance be placed at least partly in the liquid 10. As the drawing shows, the washing conveyor 11 placed at least partly in the liquid 10 leads the stack 3, which is pushed against that conveyor 11 by the liquid 10, in a transport direction M through the liquid. This liquid 10 functions as cleaning liquid. The washing conveyor 11 may for instance comprise a drive mechanism for steering the washing conveyor 11.

A direction which the (preferably completely immersed) stack 3 can follow in the liquid 10 is schematically indicated with an arrow L which indicates that the stack 3 (as a result of the fall) for a moment shoots through in the liquid 10 and by the liquid 10 is pushed up again against the washing conveyor 11 (in particular against a part of that washing conveyor 11 facing down, through upward force). This washing conveyor 11 is configured to carry along the stack 3, pushed against it, in the direction S (through the basin, in a direction away from the drop tower 1). As the drawing shows, the stack 3 being in the liquid can remain intact, for example in a nested condition of the respective objects (as shown in

FIGURE 1). In other words: the stack 3 is preferably not singulated during the stack transport carried out by the washing conveyor 11.

At an end of the washing conveyor 11 (not represented), there is for instance provided a device, not shown, for taking up and further

transporting this stack 3. Depending on the purpose and the use, the trays treated as described above may each individually be cleaned once more, or also as a stack, duly cleaned, be discharged and stored.

Such a washing conveyor 11 may for instance be endless, and may be configured in different manners, which will be clear to a person skilled in the art.

Also, a part of the conveyor 11 may extend above the liquid 10 that is in the basin (as is shown in the drawing).

To a person skilled in the art, it will be clear that the method and the apparatus as described above may be considered as involving a pre-cleaning, or also a soaking treatment. Also, turbulences may be applied in the cleaning liquid, for example by gas input with a gas injecting unit, or with a paddle wheel, to further improve and shorten the method of cleaning.

In a further exemplary embodiment, a (stack engaging) transport part of the washing conveyor 11 extends (at a relatively short distance) above the surface of washing liquid 10 contained in the basin 9. In such an exemplary embodiment, a stack 3 of objects may, during use, also be led under the washing conveyor 11, so as to be pushed against the washing conveyor by upward force, and to be carried along by the washing conveyor 11 in the discharge direction S (the stack 3 may then still be substantially immersed in the liquid 10). This configuration has also been found to achieve the purpose of cleaning or also pre- soaking to a sufficient extent, while wear on the conveyor 11 is thereby reduced. This setup and method are also set forth in the appended claims.

In a yet further use of this invention, also objects having a density greater than that of the liquid being in the basin can be used, whereby in particular the objects are stackwise dumped (i.e. make a falling motion) into the liquid. In such a case, the objects can:

either end up on the bottom of the basin so that for transport with a washing conveyor 11 engaging from above, additional object guiding measures may be provided, for example comprising smooth basin bottom parts, and/or freely rotating carrying rollers for supporting the objects;

or the objects land on the washing conveyor (for example on an upwardly facing transport part of a washing conveyor ), with the washing conveyor situated in the liquid, for example on, in or near the bottom of the basin 9, to effect the displacement of the objects.

As already mentioned above, also a method and apparatus for cleaning having only a washing conveyor may be used (namely, without use of a drop device and/or the dropping of a stack of objects into the liquid). The associated conditions and circumstances are then comparable to those already mentioned hereinbefore.

To one skilled in the art, it will be clear that the invention is not limited to the above- described exemplary embodiments and that various alterations are possible within the scope of protection of the appended claims.