The present invention relates to a gripper for picking up, transporting and depositing trays, for example trays for eggs.

Further, the present invention relates to a method for placing trays in boxes with a gripper.

A gripper of this type is known in this field of technology by the name of FLEXGRIPPER as newest development of the MR12 series, and is marketed by MOBA, see also www.rrioba.ni .

Further, in EP1832534 a gripper is elucidated with the history preceding it. In the FIGURES of the patent document it can be seen immediately what the improvements in the processing of trays were at that time, namely, on the one hand the reliable supporting at picking up and displacing, and on the other hand the reliable and gradual depositing on a supporting surface. Further, it is noted that such a tray is slightly compressed, thereby sags down a little, and thus improves the gradual placing of such a tray loaded with eggs. The egg breakage previously caused by more jolted deposition is thereby counteracted still more. In these FIGURES, however, it can also be seen that the gripper plates which support the tray with an edge part at the underside also move slightly outwards at deposition and at withdrawal. This last has become more and more of a problem over the last years, specifically where volumes for packing, stacking, and bulk transport are being optimized.

Especially in the export trade, use is made of sizes of boxes that fit only barely around trays loaded with eggs. It has been found that increasingly, proportionally compact trays are manufactured and used for the export trade mentioned. Usually, such export trays have smaller outside dimensions and they are less flexible. In particular for the placing of these trays loaded with eggs, corresponding requirements are to be met by the grippers processing such trays. It has been established that existing grippers as mentioned above cannot offer this manner of processing.

For such situations, the present invention provides a gripper that is characterized by the features of claim 1. According to an aspect of the invention, the gripper edges at their ends comprise recesses with at least an upper edge which are guided over the plate ends mentioned and which at least upon passing thereof cause the gripper edge to move against the corresponding tray edge. In a highly suitable manner, with such a gripper, for instance, egg-loaded trays can be placed in a tight outer box without risking further damages to the box, to the tray, or to eggs.

For the above-mentioned situation, the present invention furthermore provides a method for picking up with a gripper a substantially rectangular tray, the tray comprising nests for example loaded with eggs, for placing the tray in a close-fitting box, either on the bottom thereof or on a previously placed tray, and for retracting the gripper after placing of the tray,

wherein the gripper comprises, two by two opposite each other,

on the one hand two gripper blades which on two sides of the tray, at pickup, clamp and support the tray, with at their upper end corresponding parallel shafts for rotating and engaging, and

on the other hand two clamping plates for clamping of the respective other sides along the length thereof and functioning as spacers for the gripper plates at least in supporting and engaging the trays,

wherein the method furthermore comprises,

after placing of the tray, retracting the gripper plates, off of the tray, wherein over a first part thereof the gripper plates are moved inwards by means of the shafts and are thereby guided by the clamping plates, and wherein over a second part thereof the gripper plates are moved at least partly via tray parts inwards and upwards. With the gripper and method according to the present invention, an egg-loaded tray is picked up and clamped such,

that the trays at pickup are not clamped unduly, thereby compressed unduly, and consequently would cause more egg breakage,

that, upon moving down in the box, the outside dimensions of the whole of gripper with tray substantially correspond to the inside dimensions of the so-called outer boxes, and that in the gripper, after placing of a tray in such an outer box, upon the gripper plates being pulled in, these move with the upper edges mentioned over the ends of the clamping plates, thereby moving inwards, and thereupon move against the relevant tray parts, namely, for example, the edges or the half pillars.

The gripper edges of the gripper plates will then stand apart approximately at a width of the length distance between the ends of the clamping plates and can then be pulled up so. Upon this further pull-up and movement of the gripper, and in particular of the gripper plates, the gripper plates can come against the half pillars of a tray and thus, within the length distance mentioned, leave such a tray behind at the placement location.

In the circumstances described here, the gripper plates can be suitably pulled up between on the one hand the walls of outer boxes and on the other hand the edges or further parts of the tray without damaging the outer boxes by pushing outwards and/or clampingly moving-along the trays by their tray edges back up to some extent.

Further advantageous elaborations of the invention are described in the depending claims. Hereinafter, further details of the present invention are explained with reference to drawing figures, in which

FIGURE 1 shows an isometric view of an example of a tray as used for taking up and transporting eggs,

FIGURES 2 and 3 respectively show an isometric view and a side view of a tray in the situation of the tray being picked up,

FIGURES 4 and 5 respectively show an isometric view and a side view of a tray right after its placement for example in a close-fitting box, with the gripper plates in a first step of retracted position, and

FIGURES 6 and 7 respectively show an isometric view and a side view of the tray, likewise after its placement for example in a close-fitting box, with the gripper plates in a step of the retracted position further than that according to FIGURES 4 and 5.

In the various FIGURES, the same reference signs in each case refer to the same parts. In FIGURE 1 there is shown an isometric view of an example of a rectangular tray 1 as used for taking up and transporting eggs.

As usual, such a tray can accommodate 30 eggs E, arranged in rows and columns at right angles, with five eggs in a single direction shown here. Two opposite tray edges parallel to these five eggs (i.e., a first pair of parallel side edges of the tray) are called the odd edges 11a, lib, the two other edges (i.e., the remaining second pair of parallel side edges) are called the even edges 10a, 10b. To one skilled in the art it will be clear that such a tray can also be provided with a different number of places (nests) for eggs, with more or fewer columns and rows than the number shown in the drawing. The eggs E are placed in nests 2. The nests 2 support the eggs E over the surface parts at the pointed or rounded end while further support is provided by four upstanding edge portions arranged in a square. Hereinafter, these upstanding edge portions will be called pillars 12 and half pillars 121a, 121b, which half pillars 121a, 121b can be seen at the odd edges 11a, lib. As is well known, such trays 1 are made of pulp, cardboard, or a plastic. The material properties of such trays 1 may diverge widely depending on the material used and especially on the quality of the material used. The dimensions can also vary strongly. Precisely these two properties are decisive for the transport of the trays 1 in boxes with dimensions that fit on a pallet better, and hence are of economic benefit. For such boxes, also called outer boxes, hereinafter called 'tight', the gripper according to the present invention forms a suitable application. 'Tight' or 'close-fitting' will herein be understood to mean that the length of a relevant tray edge is approximately as long as the distance between the relevant inner walls of such an outer box.

In FIGURES 2-7, there are shown pairs of associated views of three successive situations of application of a gripper 20 according to an example of this invention, each pair comprising an isometric view from a viewpoint obliquely in front of and slightly above the tray 1 and a side view, with a view towards and against an even edge 10a.

The gripper 20 comprises a frame 21,

- having on the one hand a connecting piece to an arm or mast (known per se and not represented in the drawing), and having on the other hand an operating unit (likewise generally known and not represented) for - during use - rotating and translating at least two (opposite) gripper plates 22a, 22b arranged opposite each other, rotatable about shafts substantially parallel to two sides of such tray 1, for the above-mentioned engaging.

Each gripper plate 22a, 22b is provided with a gripper edge (or gripper end part) 24a, 24b, extending downwards from a respective joint or also seam 23a, 23b and directed inwards. The seams 23a, 23b and gripper edges 24a, 24b are parallel to the shafts mentioned. The two gripper edges 24a, 24b support the tray 1 at pick-up and displacement, at corresponding tray sides (facing away from each other). The gripper further comprises two clamping plates 25a, 25b to clamp the tray at the other two tray sides (facing away from each other). Each clamping plate 25a, 25b is provided with a respective clamping edge 26a, 26b, whose length at least along a part of the edge is equal to the length of the corresponding tray side (of a tray 1 to be engaged). As follows from the drawing, each clamping plate 25a, 25b is provided with two respective plate ends 27a, 27b (facing away from each other). The configuration is such that, during use, the plate ends 27a, 27b of the clamping plates guide the gripper plates 22a, 22b, at any rate at least at release of the tray 1. As follows from the drawing, plates and clamping edges are substantially parallel to the tray sides to be engaged by them, during use.

At pick-up of the tray 1, the clamping plates 25a, 25b are placed on a respective pair of edges of the tray 1 and enclose the tray 1 clampingly. At release, the gripper plates 22a, 22b are pulled inwards by the ends over the plate ends 27a, 27b of the clamping plates 25a, 25b.

As appears from what follows below (and the drawing), a particularly advantageous aspect of the present gripper is that the gripper edges 24a, 24b at their (lateral) ends comprise recesses (notches) 30a, 30aa, 30b, 30bb with respective upper edges 31a, 31aa, 31b, 31bb, the configuration being such that these upper edges 31a, 31aa, 31b, 31bb during use are guided over (i.e. along) the plate ends 27a, 27b and which at least upon the passing thereof cause the gripper edges 24a, 24b to move against the corresponding tray edges. In FIGURES 2 and 3, respectively showing the isometric view and the side view mentioned, a tray 1 is held clamped with a gripper 20, in the situation of pick-up of a tray 1,

with, on the one hand, two gripper plates 22a, 22b which support the tray 1 with gripper edges 24a, 24b against and over the odd edges 11a, lib, and with, on the other hand, at the two even edges 10a, 10b, two clamping plates 25a, 25b whereby two adjoining clamping edges 26a, 26b press on upper surface parts of the even edges 10a, 10b and whereby vertical plate parts of the clamping plates 25a, 25b press against sidewall parts of pillars 12.

In this manner, a tray 1 is firmly retained and clamped at all four rectangle sides. Clearly, the gripper plates 22a, 22b and clamping plates 25a, 25b form substantially a rectangle and they are mutually parallel two by two.

Where the vertical parts of the gripper plates 22a, 22b pass into the gripper edges 24a, 24b there are corresponding seams 23a, 23b, likewise mutually parallel.

In the vertical position of the gripper plates 22a, 22b as drawn, the tray 1 is clamped at pick-up and can then, for example, be transported to a position where the tray 1 is to be deposited.

With the gripper 20 according to the present invention, it is possible to clamp a tray 1 such that the gripper 20 with the tray 1 clamped therein can be precisely placed in a close-fitting outer box and the tray can then be left behind without damaging the tray and possibly breaking eggs, and also without damaging this close-fitting box or outer box.

The manner in which the gripper 20 is pulled off the tray 1 will be explained more in detail with reference to FIGURES 4-7.

Further indicated are plate ends 27a, 27b on each of the two clamping plates 25a, 25b. The distance between the outer edges of these ends 27a, 27b corresponds to the length of the edges 10a, 10b on that side of the tray 1 to be engaged. What is achieved in this manner is that the tray 1 is clamped and retained precisely along the length of these even edges 10a, 10b and damage can be substantially obviated. More particularly, the gripper plates 22a, 22b are pulled against the plate ends 27a, 27b. In the case of gripper plates 22a, 22b of metal, the plate ends 27a, 27b form, upon movement of the gripper plates 22a, 22b, a metal-on-metal guide with the ends 27a, 27b as point of rotation.

Indicated furthermore are the above-mentioned recesses 30a, 30aa, 30b, 30bb, arranged at the corners of the gripper plates 22a, 22b in the respective gripper edges 24a, 24b. In the exemplary embodiment shown, the recesses 30a, 30aa, 30b, 30bb have an upper edge which coincides with the earlier-mentioned seams 23a, 23b.

To one skilled in the art it will be clear that the recesses can have shapes deviating slightly from a rectangle, that the seams can be a curvature with associated radii of curvature, that the plates will be made of suitably chosen material, namely, for example, plastic or steel types of suitable strength, having a suitable cleaning profile, and having suitable dimensions and thicknesses. Indicated furthermore is a frame 21 which is understood to mean that in this part of the gripper 20 the drive (not shown as such) for this gripper 20 is arranged. Such a drive is formed in a well known manner by, for example, servomotors, other types of electric motors, or also by pneumatics. In the situation represented in FIGURES 2 and 3, the gripper plates 22a, 22b are pulled against the ends 27a, 27b of the clamping plates 25a, 25b. In this position of the gripper plates 22a, 22b, the tray 1 is placed in an outer box. For clarity, neither in these FIGURES 2 and 3 nor in the others is an outer box represented. To those skilled in the art it will be clear that in the case where the gripper 20 places a tray 1 in a close-fitting outer box in this manner, these gripper plates 22a, 22b are wholly pressed against the walls of such an outer box. As follows from the drawing, in particular, the edges 24a, 24b of the gripper plates 22a, 22b, in this tray-engaging position, extend at a vertical level below the opposite ends 27a, 27b of the clamping plates 25a, 25b. In the next FIGURES 4 and 5, the beginning of retraction of the gripper plates 22a, 22b is shown and elucidated. The views in these FIGURES are the same as those in FIGURES 2 and 3. After a tray 1 has been placed either, as a first step of packaging, on the bottom of a close-fitting outer box or, as a next step in packaging, on a tray 1 already placed in such an outer box, the gripper 20 can be retracted. More particularly, the grip and clamping of the tray 1 itself can be discontinued and also the gripper 20 can be retracted out of the outer box, mostly vertically upwards.

Pulling away of the gripper plates 22a, 22b is carried out by at least a single drive (not represented) in the frame 21. The gripper plates 22a, 22b are then both pulled inwards into the frame 21 (i.e., the plates are pulled towards each other) whereby the gripper plates 22a, 22b are guided over the ends 27a, 27b of the clamping plates and will thereby take up an oblique position with respect to an earlier-mentioned vertical position. This oblique position is represented in FIGURES 4 and 5.

More in detail, the gripper plates 22a, 22b will on the one hand, as just mentioned, be pulled over the ends 27a, 27b of the clamping plates 25a, 25b, for example with a bracket at a shaft, which shaft is parallel to the respective tray edges 11a, lib and the seams 23a, 23b (not represented in the FIGURES), and thereby provide for the gripper plates 22a, 22b a translation movement, and on the other hand at their upper end by means of the above-mentioned shaft, rotate.

In particular, this rotating has as a consequence that in the FLEXGRIPPER as mentioned in the introduction, upon further pulling in of the gripper plates, gripper edges are going to move outwards and thereby damage the outer box as well as hinder the further inward movement of the gripper plates.

For this reason, the present invention provides, in particular, recesses 30a, 30aa, 30b, 30bb at the corner points of the gripper edges 24a, 24b where the gripper plates 22a, 22b are normally pulled over. Because of these recesses 30a, 30aa, 30b, 30bb, the gripper plates 22a, 22b, upon passing of an associated upper edge 31a, 31aa, 31b, 31bb of the recesses 30a, 30aa, 30b, 30bb, move inwards. In FIGURES 4 and 5 precisely the moment of passing of these upper edges 31a, 31aa, 31b, 31bb is represented.

Depending in particular on the type of tray 1, at least after this passing, the gripper edges 24a, 24b will come against corresponding tray parts, that is, for example, the edges or the half pillars, of the tray 1. In the exemplary embodiment shown here, these are the tray parts at the odd edges 11a, lib.

In FIGURES 6 and 7, a further situation is represented. The gripper blades 22a, 22b are pulled in and rotated in the same manner as shown in FIGURES 4 and 5 and moreover the gripper blades 22a, 22b have now also moved up somewhat while the clamping plates 25a, 25b have been held in place. The ends of the gripper plates, that is, the edges 24a, 24b, will remain within the above-mentioned length distances of these clamping plates 25a, 25b, and hence within the respective sidewalls of the outer box, and therefore not damage these. More particularly, it can be seen that the lower edges of edges 24a, 24b are just being guided over the odd side edges 11a, lib and thus rest against the half pillars 121a, 121b, or can do so, which depends on the specific dimensioning of such a tray 1. Further, it follows from the drawing that the edges 24a, 24b of the gripper plates 22a, 22b, in this position, extend partly between opposite sides (corners) 27a, 27b of the two clamping plates 25a, 25b.

It will be clear from the above that in the manner as described above the gripper 20 can be used in placing such a tray 1 in a tight outer box without thereby damaging the outer box, as well as without thereby unduly clamping the tray 1 loaded with eggs E, as a result of which damages to the tray 1 and also the breaking of the eggs E are avoided. To those skilled in the art it will be clear that the invention is not limited to the exemplary embodiments described and that various modifications are possible within the scope of the invention as set forth in the appended claims. For example, the angle which the gripper edges 24a, 24b make with a main blade of a gripper plate may be specifically chosen for the type of tray to be handled. Generally, this angle will be in the range of 0° to 75°.

Further, the recesses together can extend over an appreciable part of the total width of the gripper edges, for example over a half thereof.

KEY TO REFERENCE NUMERALS

1 tray 20 gripper 25a, 25b clamping plates 10a, 10b even side edge 21 frame 26a, 26b clamping edges 11a, lib odd side edge 22a, 22b gripper plates/blades 27a, 27b plate ends

2 nest 23a, 23b seams

12 pillars 24a, 24b gripper edges

121a, 121b half pillars 30a,30aa,30b,30bb recesses

31a,31aa,31b,31bb upper edges