Title. Destacker

The present invention relates to a system for destacking a stack of trays, for instance trays loaded with eggs,

- having a supply device for supplying and positioning consecutive stacks, - having a pick up device for destacking, with pick up elements, each following, supplied stack, while with the pick up elements, successively, at least a single tray is picked up on at least two opposite sides of the stack, and is unstacked, and wherein the destacked tray is processed further, and

- having a control that guides and positions the supply device and, in accordance therewith, drives the pick up elements and has the at least single following tray of such a stack picked up at a well-defined height.

Such a system is known from, for instance, NL7107931. In this publication it is described how stacks of trays that are filled with eggs are positioned at well defined positions on a supply conveyor. For, each time, unstacking the upper tray of such a stack, the system carries out the following steps:

• halting the supply conveyor at a position where the stack takes up a correct position relative to a gripper system; at this position, or destacking location, the stack is destacked; • destacking, wherein the upper tray is unstacked by a lever having at its end a pair of grippers, while each gripper grips such a substantially rectangular tray at two opposite sides;

- having the lever follow, each time, the same movement, viz. from a fixed gripping height to a position where the tray is set down, viz. a placing location, and thence back again; this placing location is usually located on a discharge track for the destacked trays, for instance an endless conveyor belt;

- lifting the stack to the above-mentioned gripping height after the unstacking of the last tray; this lifting is mechanically controlled in that the lever is connected to a curve follower curve disc system;

- upon lifting, rotating the stack at a suitable moment through 90° for positioning the stack with the gripping sides in the correct direction; more particularly it is noted that for the described, often occurring situation, a stack of such asymmetrical trays is stacked such that each following tray is rotated

90° relative to the preceding one; and

• supplying a following stack after the preceding stack has been completely destacked, whereby all trays have been placed on the discharge track, and whereupon the cycle of destacking is repeated.

According to the structure according to NL7107931, with the above described lifting, the stack is always lifted to the same gripping height.

However, it should be noted that precisely where stacks of trays filled with eggs are concerned, the height of these stacks can vary strongly. As, in most cases, these eggs come directly from batteries, the variety of eggs is very wide.

This means that, due to the random placing of large and small egg in the trays, the trays can not only lean over, but also trays moist from leaking eggs or also from other contaminations should be taken into account, so that the often cardboard trays will by no means retain their original shape. Hence, placing and then destacking each time at a fixed height is a risky way of processing. In order to prevent the above-mentioned circumstances, the system according to the invention is characterized in that the system comprises a camera device placed near the supply device, wherein, when passing the camera device, an image is made of at least a part of the stack, with electromagnetic radiation, whereby image signals are obtained which are processed by the control, wherein the control generates signals, viz. at least

- stack pick up signals for driving the pick up elements for picking up, unstacking and placing the at least single following tray of such a stack, and

- guiding signals for guiding the supply device. It has appeared that stacks as described hereinabove, more particularly stacks that lean over, sag, or also damaged trays can be advantageously destacked without fail with the system according to the invention.

Exemplary embodiments can have the characteristic: that the supply device comprises a lifting device for a next stack to be destacked, wherein the control further generates stack control signals for driving the lifting device whereby, for each following tray, the stack is brought to an adjustable pick up height; that the pick up height is a height fixed for the system; that with the camera device, a contour of a stack is imaged; that the camera device comprises a gate through which the supply device is fed, while the gate comprises posts on opposite sides of the supply device, with, on one side a post with transmitters and on the other side a post with receivers for electromagnetic radiation; that the post with receivers comprises a row of photocells; and/or that the camera device comprises a scanner, while at least one of the sides of the stack is scanned.

In particular the exemplary embodiment with which the stack is fed through a gate is highly suitable because of its very limited size, in particular in an environment such as that of a packing station where accessibility and lack of space are often a problem.

Further, such an electronically and computer-controlled system is a very suitable replacement for the thus far substantially mechanical systems and failure free treatment and processing is ensured.

Detection systems intended for detecting numbers and types of products that are moved over a conveyor track are known from, for instance, the brochures from Banner®, more particularly the manual entitled Handbuch fur hochauflδsendes A-GAGE® MINI-ARRAY® System, 07/05/P/N121362. In that publication, it is described how a conveyor track with products such as boxes of different shape and different size are fed through a detection gate. Such a detection gate consists of two poets, one on each side of the conveyor track, while one post comprises a vertical row of light sources and the other post comprises a vertical row of detectors, for instance photocells. When passing the gate, in accordance with the height, the beam of light rays transversely to the conveying track will be interrupted, whereby the height of such a product can be determined.

For such a use of the described detection system, only a height determination is mentioned. This determination is insufficient for effecting a completely undisturbed processing of stacks of trays as mentioned hereinabove.

Further details of the system according to the invention will be explained in further detail in the following on the basis a drawing, wherein

Fig. 1 gives a schematic side view of a preferred embodiment of the system according to the invention;

Fig. 2 gives a schematic top plan view of the set up according to Fig. 1; and

Fig. 3 gives a three dimensional view of the system according to Figs. 1 and 2. In these Figures, the same parts have the same reference numerals.

In Fig. 1, it is indicated in a schematic manner how a stack 1 with trays 2a - 2f is supplied by a supply device 3 in a conveying direction T along a camera device 4. The drawn stack 1 is built up from trays 2a - 2f for which it is indicated that they can be stacked in a somewhat unordered fashion. This

stack 1 is to be further defined by the camera device 4 to then be destacked at a location intended thereto (not represented in the drawings).

The camera device 4 consists of a gate with two posts 41, 42, respectively, for transmitting and receiving electromagnetic radiation 5, for instance infrared radiation, generated by the LEDs in the form of ray-shaped beams, and captured by as many photocells. Such a device is marketed by, for instance, Banner®, as mentioned hereinabove. With the aid of the signals of these photocells, for instance sharp contours of the side view of such stacks 1 can be composed. Further, the signals coming from the photocells are processed in a control in a manner such that herewith, drive signals for further components of the system according to the invention can be controlled. These are, in particular, guiding signals for activating the supply device 3, viz giving the correct rate of feed in the correct direction, and hence for stopping to thereupon, accelerate again. These are, further, stack pick up signals that drive a pick up device. More particularly, these are signals that activate the lever, i.e. lifting arm of a pick up head with pick up elements, for instance a gripper head with grippers, and move it to the location of the stack to be destacked. Furthermore, signals will be generated that move the pick up elements to the correct height of an upper tray to thereupon pick this up. After this, the signals, or further derived signals will drive the pick up device such that the tray is delivered and set down in the correct place.

In a further embodiment, it is also possible with further derived signals, such as stack control signals, to set the height of the stack. Depending on the distances to be travelled or, also, the type of supply device, combinations of movements of the stack and of the pick up elements can be selected. Further, in many cases, a stacking movement will be selected with which, each time, the stack is rotated through 90° because the trays generally used are stacked in a manner with which each following tray is rotated through 90° relative to the preceding one. Thus, it is possible to use fixed or

also variable pick up heights. It will be clear that with the possibility of deriving signals, several combinations of control of the system according to the invention are possible in a suitable and advantageous manner.

No Figure has been added wherein the manner of picking up, taking up, unstacking, moving, delivering and setting down trays is represented. To that end, in this field of technology, many possibilities and uses are known. While, in the above, reference has already been made to destackers, there are nowadays also uses with which robots with gripper heads are deployed.

In addition to the exemplary embodiment described hereinabove, camera devices can be used. As nowadays, many types of cameras with built-in processing units are known, a system according to the invention can also be composed therewith. It will be clear to the skilled person that, depending on speeds, precision and requirements, such a solution can be opted for. Further, systems are known with which the sides can be imaged in a different manner than mentioned hereinabove, more particularly by scanning at least one of these sides.

It will be clear to any skilled person that minor modifications to the described elaborations or variants thereon are also understood to fall within the scope of protection of the appended claims.