The present invention relates to a load bearing structure as defined in the preamble of claim 1.

The load bearing structure according to the invention is extremely well suited for use as a load bearing and distributing base under the legs of cranes, such as mobile cranes and tower cranes, and also under the support legs of various excavators, and under the support legs of heavy machinery and equipment provided with support legs . Likewise, the load bearing structure according to the invention is extremely well suited for use also as a load distributing base below, beside or on top of air cushions or liquid cushions used for hoisting tasks or corresponding tasks. The structure according to the invention is also suited as a door structure and hatch structure and also as a wall structure and base structure, e.g. for use as the base and/or floor structure of an elevator car.

According to what is known in the art, solid wooden, solid plastic or solid metal, e.g. aluminium, bases as are used as load bearing bases. Wooden bases of sufficient thickness and sufficient size are extremely heavy and awkward to use, and nevertheless are not able to distribute the load evenly enough, in which case the bases do not last long in use but instead wear unevenly, particularly in those locations that are subjected to the largest loads. Solid plastic bases are more durable than wooden ones, but are even heavier and, for this reason, more awkward to use. Furthermore, they do not withstand sub-zero temperatures, but instead break easily in cold weather when stressed. Correspondingly, aluminium bases made of solid material are also very heavy and, for that reason, awkward to use. Owing the aforementioned problems, it has been a general aim to develop solutions for lighter and more durable load bearing bases. One such solution is disclosed in German patent specification no. DE102009003087A1. This discloses a load bearing base having a surface plate and a base plate and between them a support structure, in which in the center of the base is one longitudinal I-beam and two transverse I-beams and also honeycomb parts as a filler, the honeycomb parts filling all the free space between the surface plate and the base plate. In addition, the base has end beams and side plates, with which the base is enclosed into a sealed structure. A problem in this structure is that although the base is light to handle it does not withstand large loads, but instead can fail locally under load at the point of the honeycomb structure, because the heavier-duty load bearing profiled beams are only in the center of the base in the longitudinal and transverse direction. Furthermore, the transverse beam is not a single piece, but instead is composed of two halves, which detracts from the durability of the structure.

The German patent specification no. DE4021937C1 discloses another load bearing base according to prior art. This base has vertical support battens in the longitudinal direction between the surface plate and the base plate, the support battens in turn being supported by diagonal battens. This structure certainly withstands local buckling, caused e.g. by compression, in the longitudinal of the support battens, but not so well in their transverse direction, so the structure is not sufficiently durable. For example, the structure according to Figs. 1 and 2 can fall sideways to the left under a large load and, correspondingly, the structure according to Fig. 3 can collapse completely. The object of this invention is to eliminate the aforementioned drawbacks and to provide a lightweight, easy-to-handle structure with good load-bearing capability, provided with a plurality of support battens essentially the length of the whole structure in its longitudinal and transverse directions, the support battens being fitted precisely to each other at their intersection points in such a way that the longitudinal support battens support the transverse support battens and vice versa. The load bearing structure according to the invention is characterized by what is disclosed in the characterization part of claim 1. Other embodiments of the invention are characterized by what is disclosed in the other claims. One great advantage of the solution according to the invention when using the structure as a base is, inter alia, the extremely good endurance to load-induced compression enabled by the internal cellular structure combined with its lightweight construction and handling ease. The base is thus easy to transport to a worksite and it is easy for one man to install it e.g. under the support leg of a mobile crane. Another advantage is good wear resistance and weather resistance. In addition, one advantage of the structure according to the invention is good rigidity, in which case the structure can be used, when suitably modified, for many different purposes, e.g. as a wall structure, base structure, floor structure, door structure, cover structure and hatchway structure, and also as a ramp structure.

In the following, the invention will be described in greater detail by the aid of some embodiments and by referring to the attached simplified drawings, wherein Fig. 1 presents an oblique view from above of one structure according to the invention as a load bearing base,

Fig. 2 presents an oblique and simplified view from above of a load bearing base according to Fig. 1, without one edge and without the surface plate,

Fig. 3 presents a part of one longitudinal core inside the base as viewed from the side and two transverse cores as viewed from the end, Fig. 4 presents a top view of the intersection point of the one longitudinal core and two transverse cores according to Fig. 3 in such a way that one of the transverse cores is removed,

Fig. 5 presents a plurality of different core profiles, as viewed from the end, that are suitable for use in the solution according to the invention, and

Fig. 6 presents one additional support solution for use in the base according to the invention, as viewed from above without the surface plate.

Figs. 1 and 2 present an oblique top view one load bearing base according to the invention, in which the load bearing structure according to the invention is used. The base is a structure resembling a straight slab, the structure being mainly hollow inside, metallic, e.g. fabricated from steel, and essentially rectangular. The base comprises e.g. a surface plate 1, a first and a second side wall 2, a first and a second end wall 3 and a base plate 4, which elements are fastened to each other, e.g. by welding, to form an enclosed hollow box-type structure. There is preferably roughening la or some other corresponding surface patterning on the top surface of the surface plate 1, which patterning improves the grip of the surface plate 1 and simultaneously improves the ability of a crane foundation, or corresponding structure, to stay on top of the base. For stiffening the structure of the base and for ensuring the load resistance of the structure, inside the aforementioned box-type structure is a plurality of first, i.e. longitudinal, profiled battens 5 functioning as support elements receiving a compressive load at a set distance from each other, and a plurality of second, i.e. transverse, profiled battens 6 functioning as support elements receiving a compressive load at a set distance from each other. The first profiled battens 5 are essentially the length of the whole base and the second profiled battens 6 are essentially the width of the whole base. The profiled battens 5, 6 are essentially single- piece profiled battens having cuttings suited to the purpose at their intersection points.

In this application the term profiled batten refers to a shaped member that has some certain cross-sectional profile differing from a straight slab profile, e.g. a U-profile, I-profile, X-profile, modified X-profile, Z-profile or some other cross-sectional profile suited to the purpose.

Preferably the profiled battens 5, 6, i.e. the cores, are fabricated from metal, e.g. from steel. The longitudinal profiled battens 5 are at a right angle to the transverse profiled battens 6, in which case the profiled battens 5, 6 disposed in a crisscross manner form a cellular support structure inside the base, the support structure supporting in the lateral direction and having good load bearing capability. All the profiled battens 5, 6 are provided with a flange essentially in the direction of the plane of the surface plate 1 and the base plate 4, the flange extending essentially in the sideways direction, as do the top flange 5a, 6a and bottom flange 5b, 6b presented later in Figs. 3- 5, which flanges facilitate assembling the base by welding, because the welding is performed through the surface plate 1 and the base plate 4, in which case a concealed wide flange is easier to target than the narrow edge of a thin plate would be if a thin slab-shaped plate were the support batten.

The flanges 5a, 5b, 6a, 6b facilitate assembly of the base also in other ways than by welding. Thanks to the flanges 5a, 5b, 6a, 6b, the base can also be easily assembled e.g. by stapling, by gluing, with screw joints or in some other suitable manner, because the flanges 5a, 6a and the surface plate 1 as well as the flanges 5b, 6b and the base plate 4 have a lot of surface touching each other. Owing to the flanges 5a, 5b, 6a, 6b extending in the sideways direction, however, these type of profiled battens are not disposed in a crisscross manner with each other for their full lengths in solutions according to what is known in the art, but instead it has been necessary to truncate the profiled battens oriented in one of the directions, as is presented, inter alia, in the aforementioned German patent specification no. DE102009003087A1. Truncation of the profiled battens, however, degrades the durability of the base.

Preferably all the profiled battens 5, 6 are similar to each other at least in height, width and profile shape, even though they can also be different to each other. However, the length of the longitudinal profiled battens 5 can be of a different magnitude, e.g. longer than the length of the transverse profiled battens 6. Between the intersecting longitudinal and transverse profiled battens 5, 6 are rectangular hollow spaces 7, which can be filled with insert material. Figs. 3 and 4 present a part of one longitudinal core 5 inside the base as viewed from the side and of two transverse cores 6 at their intersection points with each other. To aid illustration, however, Fig. 4 presents one of the intersection points without the transverse core 6.

The longitudinal profiled batten 5, i.e. the longitudinal core 5, is e.g. essentially Z-shaped in its cross-sectional profile, or a mirror image of a Z-shape, in which profiled batten 5 is an essentially vertical web 5c and on the top end of the web 5c is an essentially horizontal top flange 5a extending in one direction and on the bottom end of the web 5c is an essentially horizontal bottom flange 5b extending in a second direction. The transverse profiled batten 6 is essentially similar to the longitudinal profiled batten 5 in its profile and cross-sectional size, also comprising a web 6c and on the top end of the web 6c an essentially horizontal top flange 6a extending in one direction and on the bottom end of the web 6c an essentially horizontal bottom flange 6b extending in a second direction.

At the intersection point of the longitudinal profiled batten 5 and the transverse profiled batten 6 is a cutting 8 in the top edge of the longitudinal profiled batten 5, in which cutting 8 is both an aperture 8a for the top flange 6a of the transverse profiled batten 6 and also an aperture 8b for part of the web 6c of the transverse profiled batten 6. The aperture 8a is in the top flange 5a of the longitudinal profiled batten 5 and the aperture 8b is in the top part of the web 5c of the longitudinal profiled batten 5, extending essentially to half the height of the web 5c. A corresponding cutting 8 is also in the bottom edge of the transverse profiled batten 6 for the longitudinal profiled batten 5. In this case the aperture corresponding to the aperture 8a is in the bottom flange 6b of the transverse profiled batten 6 and the aperture corresponding to the aperture 8b is in the bottom part of the web 6c of the transverse profiled batten 6, extending essentially to half the height of the web 6c.

Thanks to the cuttings 8, the longitudinal cores 5 and transverse cores 6 can be situated in a crisscross manner with each other in such a way that, despite the horizontal flanges 5a, 5b, 6a, 6b of the cores, the height of the lattice structure formed by the cores 5, 6 is the same as the height of an individual core 5 and 6. Also thanks to the cuttings 8, the longitudinal cores 5 and transverse cores 6 support each other at their intersection points, so that the risk of local buckling of the cores is reduced and compression endurance improves.

The cores 5 and 6 and also the cuttings 8 are made in such a way that one edge of the transverse cores 6, i.e. for example the top edge formed by the top flange 6a, is intact for the whole length of the core 6 despite the intersection points, and also one edge of the longitudinal cores 5, e.g. the bottom edge formed by the bottom flange 5b, is likewise intact for the whole length of the core 5 despite the intersection points. Also the inverse edges can in the same manner be intact, i.e. the bottom edge formed by the bottom flange 6b of the transverse core 6, in which case the other intact edge is the top edge formed by the top flange 5a of the longitudinal core 5. Likewise the webs 5c and 6c of the cores are intact from half the height of the web for the whole length of the cores 5, 6.

The overall height of the core structure of the cores disposed in a crisscross manner in their position in the base is the same as the height of an individual core 5 and 6. Essentially as much material is preferably cut away as the material of the intersecting core at the intersection point . Fig. 5 presents an end view of a plurality of different core profiles 5 and 6, i.e. profiled battens, suitable for use in the solution according to the invention. What all the profiled battens, i.e. the cross-sectional profiles of the shaped members, have in common is a top flange on the top end of the profile, which flange is marked with the reference a, and a bottom flange on the bottom end, which flange is marked with the reference b, as well as a web c between the top flange a and the bottom flange b. Fig. 5a presents an I-profile as a core 5, 6, which is assembled e.g. by welding two U-profiles placed with their webs c face-to-face. Correspondingly Fig. 5b presents an I- profile, having an essentially thick web c in addition to a top flange and bottom flange. Fig. 5c presents a conventional U-profile, in which the web c is in a vertical attitude and both the top flange a and bottom flange b are in a horizontal attitude, and Fig. 5d presents the inverted Z-profile seen in earlier figures, in which the web c is also in a vertical attitude and both the top flange a and bottom flange b are in a horizontal attitude.

Fig. 5e presents a variant of the profile according to Fig. 5a. The profile resembles a modified letter X and is composed of two profiles of U-profile type placed with their webs c face-to-face, but now the profile is reinforced with regard to durability against local buckling in such a way that the web c of both part profiles has been bent, on the top part and bottom part of the web c, into an angle outwards from the contact line of the webs c of the part profiles. The bent part d is at an angle of e.g. 20-45 degrees with respect to the vertical line and extends from the top flange a and from the bottom flange b a distance towards the center line of the height of the web c of the profile, the distance corresponding to 1/8-1/2 of the height of the profile. At its largest, therefore, the bent part d is one-half of the height of the profile, in which case the profile is a pure X-shape and there is no vertical web c at all . Fig. 6 presents one base according to the invention, as viewed from above and without a surface plate 1, which base is reinforced for resistance to compression by disposing load bearing support pieces 9 in the rectangular hollow spaces 7 between the cores 5 and 6. In the solution according to the embodiment the support pieces 9 are disposed in four spaces 7 near the center part of the base, but there could just as well be fewer support pieces 7, i.e. one, two or three, or more than four. The support pieces 7 can be e.g. of wood that withstands compression well, of metal or plastic, e.g. material made from recycled plastic, or of some suitable composite material.

It is obvious to the person skilled in the art that different embodiments of the invention are not limited to the example described above, but that they may be varied within the scope of the claims presented below. What is essential is that the structure is lightweight and withstands compression and wear well. In this case when used e.g. as a base, the base is lightweight and easy to handle. A preferred structure is therefore an essentially hollow steel structure, inside which are metal profiled battens disposed in a crisscross manner, the battens receiving compressive load well and functioning as a cellular support structure. It is obvious to the person skilled in the art that the load bearing and lightweight, but durable and rigid, structure according to the invention can be used for other purposes than just as a detached load bearing base. The structure according to the invention can be used when suitably modified e.g. as a wall structure, base structure, floor structure, door structure, cover structure and hatchway structure, and also as a ramp structure and as various platforms, transport bases and stiffeners. The structure according to the invention is also suitable for various gate structures and e.g. as a pressure-resistant protective structure. In this case the applications can be for example: wall/base of a pallet, base of a balcony, wall/base of a container, wall/base/floor of an elevator car, hatch/door (more particularly a pressure- proof/explosion-proof hatch/door), transportation base, crane foundation, stiffener for a vehicle door/wall, working platform, driving ramp.