Such a pivotal top wall is known from the publication WO 00/30945. In this case, the top wall is provided with two symmetrically disposed guide rods intended for guiding the top wall during its pivoting between the first and second positions. However, it has proven that it is relatively strenuous and difficult work to open and close this known top wall. Furthermore, the underside of the top wall and especially the outer edge of the top side of the first side wall are worn at opening and closing of the top wall. If the container is made of galvanized iron, the wear faces of the container are subjected gradually to corrosive attacks as the zinc is liable to be worn off.

In one aspect according to the invention, a top wall of the kind mentioned in the opening paragraph is provided that can be opened and closed without great effort and difficulty.

In a second aspect according to the invention, a top wall of the kind mentioned in the opening paragraph is provided that is arranged in such a way that the wear caused on the wear

faces between top wall and container at opening and closing of the top wall is minimized.

The novel and unique features according to the invention, whereby this is achieved, is the fact that the first pivot connection of the first guide rod is located at a shorter distance from the back of the top wall than the first pivot connection of the second guide rod.

The two guide rods cooperatively guide the pivoting motion of the top wall and as their pivot connections are located with a mutual spacing, seen in the pivoting direction, the pivoting top wall is affected by a reactive moment reducing the operator's efforts in opening and closing the top wall.

In first position, the top wall is resting on the top sides of the side walls with its full weight. Thereby, a considerable friction between said parts is created, whereby the operator is strained severely when the top wall at beginning of opening or final closing must be pulled or pushed across said top sides.

If the spacing between the first pivot connection of the first guide rod and the front of the top wall is greater than the horizontal spacing between the second pivot connection of the guide rod and said front in the first position of the top wall, it is advantageously obtained that the first guide rod will keep the front of the top wall lifted free of the top side of the side wall in this pivoting phase whereas the back will continue to rest on the top sides of the side walls. Thereby, the friction between the top wall and the outer edge on the top side of the first side wall is reduced to a considerable extent. At the same time, the wear on the outer edge of the front of the first side wall is advantageously reduced to a minimum.

At further pivoting of the top wall, the reactive moment from the two guide walls will also lift the back of the top wall free of the top sides of the side walls, whereby the above friction will disappear completely at least within a large pivoting angle.

During a later pivoting phase, the top wall can again slide on the outer edge of the top side of the first side wall. But then the top wall will be at such a large angular distance from its closing position that the top wall will now slide on said outer edge under the influence of only a smaller weight component. Therefore, no appreciable wear on the wear faces of the container will be able to be caused in this phase either.

The top wall is lifted safely free of the top sides of the side wall if the first guide rod is shorter than the second guide rod, whereby the first pivot connection of the first guide rod will describe a more curved path than the first pivot connection of the second guide rod, and the first pivot connection of the first guide rod is therefore preliminarily lifted more than the first pivot connection of the second guide rod.

If the first and second pivot connections, respectively, of the two guide rods are disposed in such a way that the two rods never will converge mutually in the direction extending from their second to the first pivot connection during the pivoting of the top wall back and forth between its first and second positions, it is obtained that the guide rods are not able to lock the top wall in any of its pivoting positions.

Such an arrangement of the guide rods is advantageously obtained if the spacing between the two first pivot connections is greater than the spacing between the two second pivot connections.

For locking the top wall in its first position, a projecting dowel can be located on either side of the top wall and upwardly extending lock fittings for each dowel and having a mainly horizontal slot can be located on either side of the top wall for receiving the corresponding dowel when the top wall is in its first position.

In one embodiment, the first pivot connection of the guide rods can be designed as pins pivotally journaled in each their bearing but in an advantageous second embodiment, the pins can, however, be both pivotally and displaceably journaled in each their slot. Thereby, it is obtained that the projecting dowels of the top wall at the beginning can be pulled horizontally free of the corresponding slots in the upwardly extending lock fittings on the top sides of the underlying side walls, and that the first guide rod preliminarily can lift the front part of the top wall whereas the pin of the second guide rod will slide in its associate slot.

By disposing both a first and a second guide rod at either side of the upright sides of the first side wall, an especially reliable guiding of the pivot motions of the top wall is obtained.

The top wall can furthermore be guided sideways in relation to the side walls by means of guide fittings extending upwardly on either side of the first side wall. On either side of the back of the top wall, a catch can furthermore be disposed on either side of the back of the top wall for locking engaging the corresponding guide fittings when the top wall is in second position.

The invention will be explained in greater details below, describing only exemplary embodiments with reference to the drawing, in which

Fig. 1 is a perspective view of a container having a pivotal top wall according to the invention, Fig. 2 is an end view of the container in fig. 1 having the top wall in a first position in which the container is completely closed, Fig. 3 is a fractional view of the container in fig. 2 in a first pivoting phase, Fig. 4 is a fractional view of the container in fig. 2 in a second pivoting phase, Fig. 5 is a fractional view of the container in fig. 2 in a third pivoting phase, Fig. 6 is a fractional view of the container in fig. 2 in a fourth pivoting phase, Fig. 7 is a fractional view of the container in fig. 2 in a fifth pivoting phase, Fig. 8 is a fractional view of the container in fig. 2 in a second position in which the container is completely open, and Fig. 9 is a fractional end view of how the guide rods and their pivot connections are located in both the first-and second positions of the top wall.

In the following, the invention is described on the merely exemplary assumption that the container is a collapsible container that, as the partly open container in fig. 1, has four side walls 1,2, 3,4 pivotally mounted on a base frame 5 and also a top wall 6 made in one piece for closing the container at the top, and that is of the kind that can be collapsed in empty state (not shown) so that the side walls

and the top wall will lie in a stack on top of the base frame.

In this collapsed state, the container occupies relatively little space whereby a considerable reduction in the costs for transporting the empty container is obtained.

However, it should be noted that the invention just as well can be applied to any other container having side walls, a base, and also a top wall which is made in one piece and can be brought down along the side of the container from a closed - to an open position. Thus, the container can also be of the kind that is not designed to be collapsed.

In this case, the base frame 5 is designed as a pallet having legs 7 allowing insertion of the fork arms of a fork-lift truck (not shown) under the base frame so that the fork-lift truck can lift the container.

In the shown case, the side walls 1,2 3 and 4 are each constructed around a rectangular bar frame 8 with obliquely placed reinforcing bars 9 and plate-shaped panels 10.

The collapsible container can be of any kind known per se and will therefore not be described in detail here.

The top wall 6 is constructed around a bar frame 11 with a plate-shaped panel 12 and is pivotally connected to the side wall 1 via first-and second guide rods 13 and 14, of which only the first pair is shown in fig. 1.

Figs. 2-8 are more detailed end views of some phases during the pivoting of the top wall 6 from the closed, first position in fig. 2 to the open, second position in fig. 8.

The top wall has a front 15 and a back 16. In the first position in fig. 2, in which the top wall 6 is closing the container, the top wall is resting on the top sides of the

side walls with the front 15 on the top side 17 of the first side wall 1 and the back 16 on the top side 18 of the second side wall 2.

In the closed, first position of the top wall, the top wall 6 is kept locked to the underlying side walls 3,4 by means of lock fittings 19 extending upwards on either side and a dowel 20 engaging a slot 21 tapering in direction towards the back 16 of the top wall 6 in the case shown.

At the top, guide fittings 22 are furthermore disposed extending upwards on either side of the first side wall 1, these fittings are for keeping the top wall 6 in place in a guided manner in relation to the first side wall 1 during the pivoting back and forth between the first and second positions.

A catch 23 is furthermore located at either side at the back 16 of the top wall 6. In fig. 8, said catch is engaging the guide fittings 22 when the top wall 6 is in its second position in which the container is completely open. The top wall is thereby fixed securely to the first side wall and thereby the container when the top wall is brought down to its second position.

The first guide rod 13 is pivotally connected to the top wall 6 via a first pivot connection 24 and to the side wall 1 via a second pivot connection 25.

The second guide rod 14 is pivotally connected to the top wall 6 via a first pivot connection 26 and to the side wall 1 via a second pivot connection 27.

The first pivot connections 24 and 26 of the two guide rods are designed with swivel pins, 28 and 29 respectively,

pivotally and displaceably journaled in each their slot, 30 and 31 respectively.

As shown in fig. 2, the first pivot connection 24 of the first guide rod 13 is located at a shorter distance from the back 16 of the top wall 6 than the first pivot connection 26 of the second guide rod 14. Furthermore, the first guide rod 13 forms an acute angle of e. g. 30° with the first side wall 1.

When the top wall 6 is to be brought down from the closed, first position in fig. 2 to the open, second position in fig.

8, an operator (not shown) will at first pull at the top wall so that it is displaced translationally along the top sides of the side wall in the direction of the arrow in fig. 3.

Thereby, the dowels 20 of the top wall are pulled out of their engagement with the slots 21 of the lock fittings 19 so that the top wall now also is allowed to pivot. At the same time, the swivel pins 28 of the first guide rod 13 are pushed to the top in the associated slots 30. During this and the subsequent pivoting motion, the top wall is guided in cross direction in relation to the first side wall by means of the guide fittings 22.

When the operator now continues to pull at the top wall in the direction of the arrow in figs. 3 and 4, the swivel pin 28 of the first guide rod 13 are pivoted about the second pivot connection 25 of the guide rod from the angular position inclining inwards in fig. 3 to the angular position inclining outwards in fig. 4, during which the first guide rod will lift the front 15 of the top wall free of the top side 17 of the first side wall 1 whereas the back 16 of the top wall will continue to rest on the top sides of the side walls 3,4.

In this phase, the first guide rod is thus carrying half the weight of the top wall. Thereby, the operator's job of

handling the pivoting top wall is facilitated, and the wear on the working wear faces between the top wall and the top sides of the side walls is reduced.

In fig. 4, the swivel pins 29 of the second guide rod 14 are pulled home in their associated slots 31, and as it appears, the first guide rod 13 is now functioning as push rod and the second 14 as pull rod. Thereby, the top wall is affected by a reactive moment from the two guide rods.

At continued pivoting of the top wall in the direction of the arrow in fig. 5, this reactive moment will lift the wall completely free of the side walls 1,2, 3,4 of the container.

Without contacting, the top wall is now moving at a distance past the upper, outer edge 32 of the first side wall, which would be subjected to a damaging wear if the top wall instead was pulled across the edge with most of its weight. The operator will have no difficulty in handling the top wall in this pivoting phase.

In fig. 6, the top wall 6 has pivoted a further angle whereby it is made to rest against the upper, outer edge 32 of the first side wall with its rear half, but as a result of the now heavily inclined position of the top wall, still with so small a weight that it will not cause much wear on said outer edge.

In fig. 7, the top wall is now in such a heavily inclined position that the first guide rod 13 now has assumed the part of pull rod and the second guide rod 14 the part of push rod, the swivel pins 28 of the first guide rod being pulled home in their associated slots 30 and the swivel pins 29 of the second guide rod pushed at the top in their associated slots 31.

In fig. 8, the top wall 6 is now pivoted in place in its second position in which the container is completely open. The top wall is now hanging down along the first side wall 1 with

the front 15 facing downwards and the back 16 facing upwards.

As shown, the catches 23 of the top wall are engaging the upwardly extending guide fittings 22 on the side wall 1 in this position, whereby the top wall is effectively fixed to this wall and thereby the container.

If the top wall is pivoted from the second to the first position to close the container again, the above pivoting motion takes place in reverse order.

To avoid the guide rods at any time during the pivoting motion locking the top wall to the container, the pivot connections of the two guide rods are disposed in such a way that the guide rods will never diverge in the direction extending from their second to their first pivot connection whether the top wall is pivoting in one direction or the other.

The first and second positions of the top wall are defined by the geometry of the respective container. The length of the guide rods and the placing of their pivot connections must therefore be able to fit both positions.

Fig. 9 is a fractional view of the placing of the guide rods and their pivot connections in both the closed, first position of the top wall and in the open, second position of the top wall in one and same view.

In fig. 9 L is the vertical spacing between the first pivot connection of the respective guide rod in the first position and second positions of the top wall, 1 is the length of the guide rod concerned or the spacing between its first and second pivot connections,

a is the horizontal spacing between the first and second pivot connections of the guide rod in the first position of the top wall, b is the horizontal spacing between the first and second pivot connections of the guide rod in the second position of the top wall, 11 is the length of the first guide rod, 12 is the length of the second guide rod, c is the vertical spacing between the first pivot connections of the two guide rods, and d is the vertical spacing between the second pivot connections of the two guide rods.

The above condition is met if the following formula applies to each guide rod (1) L = V 12 _ a2 + V 12-b2 and to the mutual relation of the guide rods (2) c - d = 11 - 12 An advantageous relation is obtained if the first guide rod 13 is shorter than the second guide rod 14, and the first pivot connection 24 of the first guide rod is located at a higher level than the first pivot connection 26 of the second guide rod.