- a frame, having on the one hand a connecting piece connectable to an arm or mast, and having on the other hand connecting units for rotating and translating at least two oppositely arranged gripper plates pivotable about parallel axes in a longitudinal direction which comprise at their lower ends engagement edges which make an inward angle φ with a plane

perpendicular to the longitudinal direction, and

- a control for rotating the gripper plates about the axes and for translating the gripper plates, towards or away from each other, in a direction perpendicular to the axes. Such a gripper is known from, for example, EP 1285870. In this patent document, in detail, a gripper is described for picking up small boxes, for instance, egg cartons, and it is mentioned that the gripper plates embrace the cartons. As in US5463847 acknowledged in the introduction of

EP 1285870, both gripper blades have end edges on the blades which are directed slightly inwards in order to properly embrace such egg cartons. Mentioned furthermore in EP 1285870 is a push-on plate to keep the cover closed upon release and placement of the cartons.

Such grippers, at first sight, seem to be suitable also for picking up stacks of layers of such egg cartons. The above grippers, however, are not suitable, because either the room to move for the processing of such packaging units is typically limited or the hand-shaped gripper plate encompasses only a limited clamping volume.

In order to improve and broaden the use of such grippers, the gripper according to one aspect of the present invention is characterized in that with the gripper plates a stack of height H of at least two layers of the patterns can be processed, the gripper plates comprising a bend line for the engagement edges, the engagement edges having a width B, with 0.5 H < B and preferably B < 0.8 H. Further, an aspect of the invention offers a gripper for which it holds that the engagement edge width B is greater than a height of a packaging unit itself.

It has been found that in a highly suitable manner such a simple

modification of the gripper plates in known grippers presently does allow stacks of such units (in particular hard-to-handle egg cartons) to be picked up and processed in a reliable manner.

Further, it will be clear to one skilled in the art that by processing stacks the processing capacity is advantageously increased.

Furthermore, the gripper of the present invention preferably has one or more of the following features:

that the inward angle φ has a value where 0° < φ < 20°, preferably

0° < φ < 10°;

that the engagement edges make a gradually curving inward angle having a curvature with a curvature radius R (in meters) with R > 0.2 m;

that furthermore a clamping unit is included which at least during placement of the stack keeps the patterns and the layers in place; and that the clamping unit comprises at least a single push-on plate. In addition, the present invention provides a method including

- at a pickup location, embracing and grasping with gripper plates a stack of at least two layers of the packaging units,

- transporting the stack to a placement location,

- placing the stack in the placement location,

- releasing the stack with the gripper plates, and

- removing the gripper.

With great advantage, layers of such hard-to-handle egg cartons are now processed in one and the same operation. Not only is the capacity thereby increased but also the burden of such difficult manual handling is ehminated.

According to further elaborations, the method according to the present invention has one or more of the following features:

that the pickup location is a box with the stack provided therein, wherein the gripper plates, prior to embracing and grasping, are moved sliding closely along the packaging units;

that the placement location is a box in which the stack is placed, wherein the gripper plates, upon release and removal, are moved away shding closely along the packaging units; and

that the pickup location comprises a stack formation location, for example a surface of a belt conveyor or of a conveyor table for forming a stack of at least two layers of the units; and

that the method is carried out with a gripper according to this invention.

Another aspect of the present invention relates to

a robot with gripper according to this invention; and

a robot for carrying out the method according to this invention. In a highly suitable manner, with such robots hard manual work can be replaced.

In the following, the present invention is elucidated in detail with reference to a drawing, showing in FIGURE 1 a schematic side view of an exemplary embodiment of the gripper according to the present invention; and in FIGURE 2 a robot provided with the gripper.

FIGURE 1 shows a non-limitative exemplary embodiment of a system including a gripper 1 and packaging units P. The gripper is, in particular, a gripper 1 for picking up, transporting, and placing patterns of a number of layers of substantially identical, block-shaped, rectangular packaging units P, for example, egg cartons. The gripper 1 is provided with a frame 2, having on the one hand a connecting piece 3, connectable to an arm or mast of, for example, a robot 500 (see FIGURE 2).

Furthermore, the gripper 1 comprises connecting units 4a, 4b for (combined) rotation and translation of two oppositely arranged gripper plates 5a, 5b, pivotable about parallel axes in a longitudinal direction. The connecting units may be implemented in different manners, with actuators, hinges, translation mechanisms, a suitable control, which will be clear to one skilled in the art. The control may for instance be, wholly or partly, part of the connecting units 4a, 4b, may be integrated in a possible robot control of the robot 500, or cooperate therewith, or the like.

Distal parts of the gripper plates 5a, 5b, namely, distal engagement parts or engagement edges 6a, 6b, each include an inward angle φ with a plane perpendicular to the longitudinal direction, at least, with respect to proximal parts of the gripper plates 5a, 5b (as indicated in the drawing). The control (which may, for instance, be part of the connecting units 4a, 4b) is provided in particular for rotating the gripper plates about the axes mentioned and for translating the gripper plates, towards or away from each other, in a direction perpendicular to the axes mentioned.

With great advantage, the configuration is such that with the gripper plates a stack of height H of at least two layers of the patterns mentioned can be processed. The gripper plates comprise a bend line for the engagement edges 6a, 6b (namely, a bend line which extends between a proximal and a distal plate part of each plate, at least, defines a separation between these arts). The engagement edges 6a, 6b have, for example, a width B, where

0.5 H < B < 0.8 H. The width B and height H are indicated with arrows in FIGURE 1.

The plate width B is, in particular, the width of the distal plate part 6a, 6b, measured from the (normally horizontal) bend line to a lower end of the plate. The stack height H is, in particular, equal to the number of layers of packaging units times the (normally vertical) height of a respective packaging unit P in the case where those units each have the same height. As follows from the example, the plate width B is, in particular, greater than a height of a single packaging unit P to be stacked. With this, good results can be obtained, for example, a stable and well controlled stack engagement. In FIGURE 1 gripper 1 comprises a frame 2 with a connecting piece 3 which can be connected, for example, to a robot arm (see FIGURE 2).

With this gripper 1 a stack of layers of packaging units P is clamped, grasped, transported, and put down again. These packaging units P are, for example, egg cartons of the known type of 2 x 3, or 2 x 4, 2 x 6, etc., type which have been filled with eggs in special egg handling machines and where the covers are properly closed. Such packaging units are thereupon arranged in patterns, such that these patterns can be placed, for example, in boxes, also called overpack or outer boxes, or can also be combined to form larger wholes on pallets. Such packaging units are to be regarded as being substantially block-shaped, with a bottom half and a cover half generally beveled slightly because they form an assembly of product nests, i.e., egg nests in the case of eggs. These patterns, because of the shape of the units, will be generally rectangular and thus be picked up at two opposite sides. In the case where stacks are processed, these stacks will likewise possess a shape corresponding to that already composed per layer, so that in that case too, a stack will be picked up at two opposite sides, carried, and put down again. In the present FIGURE 1 a side view is shown of the long side of such packaging units P, with gripper plates 5a, 5b clamping the units of the stack (of two layers, in this case) on their short sides. This may involve, for example, patterns of two layers of four cartons each. To those skilled in the art, it will be clear that other patterns are possible.

More particularly, the gripper 1 comprises two oppositely arranged, substantially straight gripper plates 5a, 5b, which can be controlled with a schematically indicated control and respective connecting units 4a, 4b. This control and these connecting units provide for the rotation of the plates 5a, 5b, in and out, respectively, to embrace or release a stack of packaging units P, and to displace the plates 5a, 5b towards or away from each other, or to embrace and grasp or to release the stack, for instance with rotation about axes at the location of the connecting units 4a, 4b, substantially

perpendicularly to the plane of the paper of FIGURE 1. Unlike in the case of grippers known and widely used in this field of technology, the gripper plates 5a, 5b comprise ends or gripper edges 6a, 6b of a considerable width B, precisely to be able to pick up stacks of height H of several layers. It has been found that a width B between 0.5 H and 0.8 H is very suitable for such stacks, in other words, a width B that is greater than a height h of a stack-packaging unit P. In the example, the width B is less than 1.6 h.

Furthermore, to accommodate the typically limited room to move for these grippers 1, for example in tight-fitting boxes or crates, the present invention provides a transition between the straight part and the edge with a gentle curve or a small kink 7a, 7b.

In the case of a kink, the edge basically runs on and a small angle φ is provided having values where 0° < φ < 20°, preferably 0° < φ < 10°.

In the case of a gentle curve in the transition of the straight art to the edge, the curvature has a curvature radius R (in meters) with R > 0.2 m. With the properties as elucidated hereinabove, the gripper plates 5a, 5b, especially upon removal thereof after placement in a placement location, i.e., in a tight -fitting box or crate, and release of a stack, whereby the gripper plates 5a, 5b are simultaneously moved up and turned inwards, in short, with simultaneous translation and rotation, can be taken away without damaging the packaging units or the box or crate.

Similarly, layers can be picked up from such a box or crate, referred to as a pickup location, whereby the gripper plates 5a, 5b, in order not to damage the box, in the same way as above for the purpose of the retraction

movement, but now for the purpose of embracing and picking up, must be translated and rotated whilst carefully sliding between the walls of the box and the packages.

It is precisely the slight bend 7a, 7b to the edges 6a, 6b that makes such a careful operation possible.

In an exemplary embodiment not further shown in the drawing, a clamping unit or push-on plate is provided in the manner as described in EP 1285870, allowing both the covers of such egg cartons to remain clamped and the shape of the stack to be retained in a simple manner.

In yet another exemplary embodiment, a holder strip 8 is included as represented in FIGURE 1 in broken lines. Such a strip rests on and pushes against these cartons P, whereby on the one hand a substantially horizontal confinement of the stack is obtained, and whereby on the other hand the covers are thus kept closed and the stack is held in the pattern thereof. Such a strip is, for example, of stainless steel, and comprises, in one piece, an upper part 8a and a lower part 8b with a bend 8c therebetween. The lower part 8b in this side view buckles "forward" and thus has the bend resting at a particular angle on the side of a cover of such an egg carton P. The upper part 8b is operably mounted in frame 2, and can for instance be moved vertically down and up, and/or be rotated slightly about a horizontal axis, in these drawings perpendicular to the axes as mentioned hereinabove.

It will be clear that in the depicted example there is such a strip 8 on each of the two sides of such a layer of packaging units P.

A robot as mentioned may in itself be implemented in different manners, which will be clear to one skilled in the art. FIGURE 2 shows an example of the robot 500, in this case a robot with at least four axes, for example a 4-axis robot, known per se, with multiple mutually movable robot parts 501, 502, 503, 504, in particular parts that are rotatable or pivotable relative to each other about axes XI, X2, X3, X4. In the example, the robot 500 comprises a base 501 on which a carrier 501a of a first arm 502 is arranged rotatably about a vertical axis XI. The first arm is pivotable, by a bottom end, about a horizontal pivotal axis X2 relative to the carrier 501a. A second arm 503 is coupled by a first end to a top end of the first robot arm 502 in a manner pivotable about a horizontal pivotal axis X3. A robot head or operating arm 504 (which, in this example, holds the gripper unit 1) is coupled to a second end of the second arm 503 in a manner rotatable about a vertical axis X4. The head/operating arm 504 in this case is in itself rotatable about a horizontal axis relative to the end of the second arm 503. Obviously, the robot may also be configured in a different manner. In particular, the robot (together with a gripper 1 coupled thereto) can be utilized for carrying out a method according to the invention. It will be clear to one skilled in the art that various modifications in the gripper, the system and in the method as described above are possible within the scope of protection of the appended claims. For instance, the choice of materials in a particular application, such as well-selected plastics instead of stainless steel, can be of influence on a type of curve or kink. Further, no specific manner of drive has been mentioned, but, for example, pneumatics, hydraulics, or servo motors can be considered.