JOIST

Abstract: A joist is adapted to be used as a top joist in a sporting floor in which a plurality of floor boards (1) or panels rest on a plurality of parallel top joists (3). The top joists (3) are spaced apart and rest on a plurality of parallel, spaced-apart bottom joists (4) extending substantially perpendicular to the top joists (3) and supported on a base (5) by means of blocks (6). The joist has a narrow, upper flat surface (7) extending long the joist and adapted to engage the lower side of the floor boards or panels, and a narrow, lower flat surface (8) which extends along the joist and which is positioned directly opposite the upper flat surface and adapted to engage the upper side of the bottom joists (4). The joist has a thickness decreasing laterally outwards from these two flat surfaces (7, 8).

Description: JOIST The present invention relates to a joist adapted to be used as a top joist in a sporting floor in which a plurality of floor boards or panels rest on a plurality of parallel top joists which are spaced apart and rest on a plurality of parallel, spaced-apart bottom joists extend¬ ing substantially perpendicular to the top joists and supported on a base by means of blocks. In a prior art sporting floor of the type described above, rubber inserts are arranged between the top and bottom joists. These rubber inserts give the sporting floor the required qualities of deformation or resilience, which renders it possible to make the bottom joists more rigid and, thus, so strong that sufficient strength is imparted to the sporting floor. One problem of this prior art sporting floor is the aging of the rubber material of the inserts, which thus can become rigid or brittle, thereby losing its elastic properties.. An object of the present invention therefore is to provide a joist adapted to be used as a top joist in a sporting floor of the type described above and designed in such a manner that the sporting floor can be given both the required qualities of deformation or resilience and the required strength properties, without necessitating the use of rubber inserts. This object is achieved by a joist which is of the type described by way of introduction and, according to the present invention, is characterised in that it has a narrow, upper flat surface extending along the joist and • adapted to engage the lower side of the floor boards or panels, and a narrow, lower flat surface which extends along the joist and which is positioned directly opposite the upper flat surface and adapted to engage the upper side of the bottom joists, and that it further has a thickness which decreases laterally outwards from these two flat surfaces. In a preferred embodiment, the joist is flat-bevelled on both sides of the upper and/or lower flat surface. The ratio of joist thickness to width preferably is 1:4-1:5. The invention will now be described in more detail with reference to the accompanying drawings. Fig. 1 is a top plan view and illustrates a sporting floor in which the joist according to the present inven¬ tion is used as a top joist, and Fig. 2 is a sectional view along the line II-II in Fig. 1. The floor illustrated in Fig. 1 comprises a plurality of parallel floor boards 1, such as parquet boards, form¬ ing the floor surface 2. The floor boards 1 rest on a plurality of parallel top joists 3 equidistantly spaced from each other and extending perpendicular to the floor boards 1. The floor boards 1 are attached to the top joists 3 by means of glue or nails. The top joists 3 rest on a plurality of parallel bottom joists 4 which are equidistantly spaced from each other and extend perpendicular to the top joists 3, i.e. in parallel with the floor boards 1. The top joists 3 are nailed to the bottom joists 4. The bottom joists 4 are supported on a base 5, such as a concrete floor, by means of blocks 6 which are equi- distantly spaced from each other. The centre distance bet¬ ween the blocks 6 along the bottom joists 4 is the same as the centre distance between the top joists 3, and the blocks 6 are positioned midway between neighbouring top joists 3. In the embodiment shown in Fig. 1, each top joist 3 is composed of a plurality of joist elements 3a of the same length which are arranged successively and whose length is equal to the centre distance between neighbour¬ ing bottom joists 4. Each joist element 3a extends between and rests on two successive bottom joists 4, as illustrat¬ ed in Fig. 1. In the embodiment shown in Fig. 1, also the bottom joist 4 is composed of a plurality of joist ele- ments 4a of the same length which are arranged succes¬ sively and whose length is equal to the centre distance between the blocks 6. Each joist element 4a extends bet¬ ween and rests on two successive blocks 6, as illustrated in Fig. 1. In a preferred embodiment, the centre distance bet¬ ween neighbouring bottom joists 4 and, consequently, also the length of the joist elements 3a is 500 mm, the width of the joist elements 3a is 95 mm and their height or thickness 22 mm. Moreover, in this preferred embodiment the centre distance between the blocks 6 and, consequent¬ ly, also the length of the joist elements 4a is 420 mm, the width of the joist elements 4a is 95 mm and their height or thickness 14 mm. The joist elements 4a are rectangular in cross-section. According to the present invention, the top joist 3 has a narrow, upper flat surface 7 which extends along the joist and with which the floor boards 1 engage, and a narrow, lower flat surface 8 which extends along the joist and which engages the flat upper surface of the bottom joists 4. The two horisontal flat surfaces 7 and 8 are positioned directly opposite each other in the central portion of the top joist 3. The top joist 3 has a height or thickness which slightly decreases laterally outwards from the central portion by being flat-bevelled on both sides of the central portion both on the upper side and on the lower side. In the embodiment illustrated in the draw¬ ings, the flat surfaces 7 and 8 have a width of 30 mm and, thus, each of the bevelled lateral portions has a width of 32.5 mm. In the illustrated embodiment, the bevelling angle is about 1°. Since the top joists 3 have the cross-sectional shape described above, a narrow, strip-shaped contact surface is obtained between the top joists 3 and the bottom joists 4, whereby the force transferred from the floor boards 1 via the top joists 3 to the bottom joists 4 is centred to the centre of the joist elements 4a, which, in turn, implies that the bottom joists 4 can be given a height or thick¬ ness that is sufficient for the desired strength and yet produce the desired qualities of deformation and resil¬ ience. Since the top joists 3 have the cross-sectional shape described above, the free distance between the top joists 3 can be kept small, thereby reducing the risk of treading through, at the same time as the distance between the narrow, strip-shaped contact surfaces can be kept rela- tively great. In the illustrated embodiment, each block 6 consists of an upper, wedge-shaped wooden part 6a and a lower, wedge- shaped wooden part 6b. The upper part 6a is formed with a longitudinal groove 9, and the lower part 6b has a longi- tudinal ridge 10 engaging the groove 9. The two wedge-shaped parts 6a and 6b are displaceable relative to one another in their longitudinal direction for the purpose of adjusting the height of the block 6. As a result, the blocks 6 may be given different heights so as to compensate for any irregu- larities in the base 5. A number of joists according to the present invention are included preferably as top joists in a module which is intended for the production of sporting floors and composed of top joists 3, bottom joists 4 and blocks 6 or, alterna- tively, block upper parts 6a. The size of the module, i.e. the number of top joists, bottom joists and blocks included therein, can of course be varied as desired, but in a pre¬ ferred embodiment, the size of the module corresponds to a conventional loading pallet.

Claims: CLAIMS 1. Joist adapted to be used as a top joist in a sporting floor in which a plurality of floor boards (1) or panels rest on a plurality of parallel, spaced-apart top joists (3) resting on a plurality of parallel, spaced- apart bottom joists (4) extending substantially perpen¬ dicular to the top joists and supported on a base (5) by means of blocks (6), c h a r a c t e r i s e d in that it has a narrow, upper flat surface (7) extending along the joist and adapted to engage the lower side of the floor boards (1) or panels, and a narrow, lower flat surface (8) which extends along the joist and which is positioned directly opposite the upper flat surface and adapted to engage the upper side of the bottom joists (4), and that it further has a thickness decreasing laterally outwards from said two flat surfaces (7, 8). 2. Joist as claimed in claim 1, c h a r a c - t e r i s e d in that it is flat-bevelled on both sides of the upper and/or lower flat surface (7, 8). 3. Joist as claimed in claim 1 or 2, c h a r a c ¬ t e r i s e d in that the ratio of its thickness to its width is 1:4-1:5.

Inventors: ANDREASSON GUNNAR, GLEMBERG RONNY, ANDREASSON, GUNNAR, GLEMBERG, RONNY
Applicants: TARKETT AB
Application year: 1992
Main classification: E04F15
IPC codes: E04F15