The present invention relates to a device comprising (a) at least a first and a second element hinging connected to each other through a rotation axis and (b) a balancing device for balancing at least one of the first and second element upon rotation of at least one of the first and second element with respect to the other.

From EP-A-007.680 a balancing device is known, which is particularly suitable for balancing a platform hinging connected along a rotation axis to the frame of a truck or trailer.

In the known balancing device, the lever arm of the balancing device is connected with one end to the door to be balanced. A spring mounted to the frame is connected to the other end of the lever arm. The other end of the lever arm is engaged by and pivotally connected to a pull member, the pull member being mounted such that a pulling force exerted to the lever arm, in all positions of the arm, extends through a point on the frame, which at least during the hinge movement is fixed. In the position where the gravity centre of the member to be balanced is positioned above the rotation axis, the length along which the spring is biased is equal to the distance between the fixed point on the frame and the application point of the pull member on the lever arm in that position. Thereby, the pulling force extends in longitudinal direction of the lever arm, the spring being used in its region where it has linear characteristics.

There is however not only a need to balance a single door mounted to a frame. With the increasing number of applications there is a need to a balancing system with which a plurality of elements hinging connected through a rotation axis may be balanced, the elements not necessarily being mounted to a frame.

The present invention therefore solves the problem of providing an assembly for balancing a device comprising at least two parts, which are hinging connected to each other along a rotation axis.

This is achieved by the present invention with the technical features of the characterising part of the first claim.

Thereto the device of this invention is characterised by a balancing device comprising a lever part which is pivotally connected to a first and a second pull member. The first pull member is connected to a first spring at a first connection point and is mounted such that a pulling force exerted to the lever part in all positions of the first element extends through the first pull member and the connection point. The connection point is fixed with respect to the rotation axis at least in the course of a hinging action.

The second pull member is connected to a second spring at a second connection point and is mounted such that when a pulling force is exerted to the lever part, this pulling force in all positions of the second element extends through the second pull member and through the second connection point. The second connection is fixed with respect to the rotation axis at least in the course of the hinging action.

The first and second spring have a linear characteristic. The length 11 over which the first spring is biased being is to the distance between the first fixed connection point and the application point of the first pull member on the lever part. The length 12 over which the second spring is biased is equal to the distance between the second fixed connection point and the application point of the second pull member on the lever part. Thereby 11 may be the same as or different from 12.

In the device of this invention, two hinging mounted elements are connected by a common lever part. When rotating the first element with respect to the rotation axis, a pulling force is exerted to the first element, in particular to the first pull member. Due to the connection of the first pull member to the lever part, since the application point of the first pull member to the first spring is fixed in the course of the rotation, and because of the absence of a connection between the lever part and the spring on the one hand and any possible frame carrying the first and second element on the other hand, this pulling force causes a displacement of the lever part, which takes along the second element connected to it along the second pull member. The displacement of the lever part is possible because of the pivotable connection between the first and second pull member and the lever part. In fact, due to the presence of a common lever part, the first

and second spring and the first and second pull member co-operate to control the displacement of the first and second element.

The spring is used in the region where it has linear characteristics. Preferably use is made of a compression spring as such a spring exerts a pulling force in the closed as well as the fully open state of the cover, i. e. the position in which the first element is a continuation of the second element as well as the position in which the bottom sides of the first and second element face each other.

It is preferred that the first and second pull element have an application point which coincides with respectively the first and second fixed point.

To allow adapting the balancing needs to the dimensions and weight of the elements that need be balanced, and to the spring characteristics, the lever part comprises means for adjusting the connection of at least one of the first and second pull member to the lever part. For the same reason also preferably the spring constant of at least one of the first and second spring is adjustable.

According to a preferred embodiment at least one of the first or second element is hinging connected to at least one further element.

In that way when displacing the first and second element, the at least one further element is taken along and may be positioned in one single action together with the first and second element.

To improve force transfer between the first and second element, the lever part and rotation axis are pivotally connected to each other.

According to a preferred embodiment on an end part of at least one of the first and second element facing away from a part connected to the rotation axis, displacement means are provided. In that way displacement and rotation of at least one of the first and second element with respect to the other may be guided, controlled and/or facilitated.

The device of the present application is suitable for use in a wide variety of applications where two rotationally connected elements are to be balanced with respect to each other.

Further preferred embodiments of the invention are elucidated in the appending figures and description of the figures.

Figure 1 shows a cross section of a device of the present invention, the first element being a continuation of the second element.

Figure 2 shows a cross section of a device of the present invention, where the two elements are rotated with respect to each other.

Figure 3 shows a cross section of a device of the present invention, the two elements laying against each other.

Figure 4 shows a lifting device using the device of this invention.

As is shown in the preferred embodiment of figure 1, the device of the present invention comprises a first 1 and a second element 2 which are to be balanced when displaced with respect to each other. If so desired, in addition to the first and second element 1,2, additional elements may be hinging connected to one or both of the first and second element 1,2 as is shown in figure 4.

The first and second element 1,2 are hinging connected to each other at a first end 39,40 and are rotatable with respect to each other around a rotation axis 3. The first and second element 1,2 may however be hinging connected on any other position on the elements. The hinging connection allows rotating the two elements with respect to each other to a larger or lesser extent. The first and second element 1,2 each comprise a top face and a bottom face 19,29. In case additional elements are added to the first and/or second element 1,2, the additional elements may but must not be balanced by a corresponding balancing device. In general a single balancing device 35 will be sufficient to balance the device shown in figure 4.

The first and second element 1,2 may take different forms and may for example take the form of a plate, a profile, a bar etc. The first and second element 1,2 may have the same or different dimensions or length and may have the same or a different weight.

The basic principle of a balancing device is disclosed in EP-A-0.007.680, which is hereby incorporated by reference.

If so desired, to facilitate rotation of the first and second element with respect to each other, to facilitate changing the position of

the first and second element 1,2 where the first element is a continuation of the second element to a position where the first and second element are located under an angle, of for example 90 or 180°, or back appropriate means may be provided on either only the first or second element 1,2 or both. A suitable example includes a grip mounted to a side face of one or both of the first and second element 1,2 which extends perpendicular to the rotation axis 3.

Rotation of the first element 1 with respect to the second element 2 will mostly takes place in such a way that the bottom faces 19, 29 of the elements are displaced towards and from each other. Simultaneously with the hinging movement of the first and second element 1,2 the rotation axis 3 is displaced. In principle rotation in the other direction where the top faces 32,33 of the elements 1,2 face each other should also be possible.

The device of this invention comprises a lever part 10 which is pivotally connected to a first and a second pull member 13,23. The connection of the first and second pull member 13,23 to the lever part may take place through a common connection point, or as is shown in figure 1-3 through separate connection points 12,22 spaced from each other. The common connection point is of use when element 1 lays behind element 2. The spaced positioning has the advantage that it is easier to have the rotation axis 3, the point 12 and 15 on one line to achieve an optimum balancing effect. The same holds for the points 3,22,25. This is illustrated in figure 1. The first and second pull member 13,23 may have the same or a different length.

The lever part 10 is a separate part which is connected to the first and second pull element 13,23. However, the lever part 10 is not attached to a framework bearing the first and second element 1,2. The loose mounting of the lever part allows the hinging movement of the first and second element with respect to each other and the displacement of the bottom or top faces of the first and second element to and from each other. The lever part 10 may take different shapes. In a possible example the top 30 of the lever part 10 has a smaller length as compared to its base 30. The top and base may however also have the same length. The lever part 10 may also be build up of a plurality of parts. The lever part 10 may be pivotally connected to the rotation axis 3. This connection is however not necessary. In the shown embodiment, the lever part 10 contains a hole for receiving the rotation axis 3 there through.

The position of the connection points 12,22 of the first and second pull member 13,23 to the lever part 10 is preferably adjustable, but must not be so and may be calculated and fixed in advance. In an adjustable mounting, a plurality of connecting points 12,22 are provided on the lever part 10.

This is done to allow for an in situ adapting of the balancing device to the properties of the device, i. e. weight and dimensions of the elements and the spring characteristics.

The first pull member 13 is connected at a first end 12 to the lever part 10 as described above. At a second position the first pull member is connect to a first spring 14, through a first connection point 15. The position of the first connection point 15 is fixed with respect to the first element 1, at least in the course of the rotation movement. This is important as it provides for the possibility of balancing the whole. A first end 22 of the second pull member 23 is connected to the lever part 10. At another position or end the second pull member 23 is connected to a second spring 24, through a second connection point 25. The position of the second connection point 25 with respect to the second element 2 is fixed, at least in the course of the rotation movement as is described for the first pull member 13.

The first pull member 13 is mounted such that when exerting a pulling force to the lever part 10, the pulling force in all positions of the lever part 10 extends through a fixed point 15 on the first element 1, the point 15 being fixed at least in the course of the rotation. The second pull member 23 is mounted such that when exerting a pulling force to the lever part 10, the pulling force in all positions of the lever part 10 extends through a fixed point 25 on the second element 2, the point 25 being fixed at least in the course of the rotation.

The first and second pull member 13,23 may take any suitable form known to the man skilled in the art and may for example comprise a pull rod or a pulling cable, which is guided over a guiding at the position of respectively the first and second fixed point 15,25. The first and second pull member 13,23 may have the same or a different length.

When displacing the elements 1,2, i. e. when rotating the first element 1 with respect to the second element 2, the points 15,25 are displaced over at least part of a circular path having the connecting points 12,22 as a middle point.

In the shown embodiment, the first 14 and second spring 24 are each mounted in a corresponding housing 18,28. This is however not necessary. The first and/or second spring 1,2 may, but must not be attached to respectively the first 1 and second element 2. When mounted thereto, the first and/or second spring 1,2 may be mounted to the top side 32,33, the bottom face 19,29 or any other face or side of the first and/or second element. The first and second spring 1,2 may be of the same or a different type. They may have the same or different spring characteristics.

The first and/or second spring 14,24 may extend parallel to respectively the first and second element 1,2. This is however not necessary and the first and second spring may in fact take any orientation adapted to the need of the device in which they are contained.

Within the scope of this invention, the wording spring is meant to include all types of elastic elements having spring characteristics, for example a gas spring, a compression spring or a pull spring or any other spring known to the man skilled in the art.

On a side facing away from the lever part 10, the first and second pull member 13,23 are preferably fitted with an adjustable nut and spring cup against which the spring 14,24 rests. At a side facing towards the pull member 13,23, the spring 14,24 preferably rests against a second spring cup.

The first and second spring housing 18,28 are pivotally mounted with respect to the lever part at the points 15,25.

Within one and the same device the distance a between the rotation axis 3 and the connection point 12 of the first pull member to the lever part 10 is constant. Similarly the distance between the rotation axis 3 and the connection point 22 of the second pull member to the lever part 10 is constant.

Both distances may however be the same or different. The distance b between the rotation axis 3 and the first fixed point 15 is constant. Similarly, the distance between the rotation axis 3 and the second fixed point 25 is constant. Both distances may however be the same or different. Distance a may be the same to or different from distance b. In the course of rotation of the first and second element however, the distance c between the application point 12,22 of the pull member and the fixed point 15,25 may vary depending on the extent to which the spring member gets compressed or expanded.

On one or more sides of an element 1,2 a grip may be provided to facilitate displacing the elements with respect to each other.

When displacing the first element 1 from the position shown in figure 3 to the position shown in figure 2, a pulling force is exerted by the pull member 13 and the pulling force is transferred by the spring 14 into a force causing a displacement of the first element in a direction pointing away from the initial position of figure 3. Simultaneously the pull member 13 is shortened by a pulling action of the spring 14, which in this case is a compression spring. The shortening effect is caused in case a cable is used as a pull member 13 and the cable is displaced over the fixed point guiding 15 towards the spring. This displacement force has its application point in the rotation axis 3. As a consequence of the displacement force, a pulling force is exerted to the second element 2 through the second pull member 23 and further to the second spring 14.

The second spring is expanded or compressed until a balanced position is achieved in case the element is left loose.

It is however also possible to use the device of this invention to achieve a displacement of a first and second element with respect to each other, by simply exerting a pulling force to one of both elements, the displacement being stopped at a certain point.

The length over which the spring, having a linear characteristic, is biased is equal to the distance between the first/second fixed point 15,25 and the application point 12,22 of respectively the first and second pull member 13,23 on the lever part 10 in that position of the first and second element.

The above described device is suitable for use in a wide variety of applications. In a first example the device may be executed in the form of a container cover, the first and second element 1,2 forming a first and second cover part. Therefore, the present invention also relates to a container comprising a top, bottom and at least one side face enclosing a central storage space, at least one of the top or side faces being covered by the above described assembly of a cover comprising at least a first and a second element, and a balancing device for balancing at least one of the first and second element. The elements are displaceably mounted on a circumferential edge of the container, which may either be a top edge in case the container comprises an open top, or a

side edge for a container containing an open side face. To facilitate displacement of the elements along the edge and facilitate opening of the container the displacement means comprise a plurality of wheels provided at the edges of the cover, the wheels being received in a corresponding rail provided along the top rim of the container. The cover is provided to cover an open face of a container, for example a top face or a side face of the container.

The device of this invention is also suitable for use as a lifting device. In that case a plurality of bar shaped elements 4, 5 are hinging connected to each other, each time in a central part 3 of the element. At the point where a first element is connected to a second element, a balancing device 10 as described above is provided. In some cases it will be sufficient to provide a single balancing device, in other cases the use of a plurality of balancing devices, each time one balancing device being mounted at a cross point, may be required. The first element may at one or both ends 6,7 be connected to a further element 8.

The second element 2 may at one or both ends be connected to a further element 9. The further element may be mounted cross wise with respect to each other as is shown in figure 4. In that case pulling apart of two opposite connection points 40, 41 or 40', 41'will suffice to erect the device of figure 4. This lifting device has the advantage that it may be erected without necessitating the use of a hydraulic device for forcing the elements apart.

The device shown in figure 4 may be rotated over 90° to obtain for example a foldable and unfoldable roof.