Pretensioned mechanical locking device for building panels

A set of building panels, wherein each building panel comprises a decorative surface and a mechanical locking device for horizontal and vertical locking of similar or essentially identical building panels in an assembled position by means of a folding and/or vertical displacement, wherein an upper edge portion of a side edge of a first building panel and an upper edge portion of a side edge of a second building panel are, in the assembled position, juxtaposed to form a joint seal, said mechanical locking device comprising:

• a locking surface at the upper edge portion of the side edge of the first building panel configured to cooperate with a locking surface at the upper edge portion of the side edge of the second building panel, wherein the two locking surfaces are configured to lock the side edge of the first building panel and the side edge of the second building panel in a direction parallel to the extension of the decorative surface,
• a locking strip, projecting outwardly from a lower edge portion of the side edge of the first building panel, comprising a locking element configured to be received in a locking groove of the side edge of the second building panel by means of said folding and/or vertical displacement,
• a locking surface on the locking element configured to cooperate with a locking surface in the locking groove, wherein the locking surface on the locking element and the locking surface in the locking groove are configured to prevent a displacement between the first and second building panels,
• an intermediate edge portion of the side edge of the second building panel comprising a surface configured to cooperate with a surface on the locking strip in the assembled position,
• wherein the locking strip is configured to be angularly displaced during the folding and/or vertical displacement, thereby undergoing an angular displacement,
• wherein the angular displacement together with the cooperation between the locking surface on the locking element and the locking surface in the locking groove are configured to create a pretension between the locking surface at the upper edge portion of the side edge of the first building panel and the locking surface at the upper edge portion of the side edge of the second building panel in the assembled position, and
• wherein a difference between an angle, relative to the extension of the decorative surface, of the surface on the locking strip and an angle, relative to the extension of the decorative surface, of the surface on the intermediate edge portion of the side edge of the second building panel decreases during the folding and/or vertical displacement,
• wherein the pretension between the locking surface at the upper edge portion of a first side edge of a first building panel and the opposite locking surface at the upper edge portion of the third side edge of a second building panel, in the assembled position, is greater than the pretension between the locking surface at the upper edge portion of a second side edge of the first building panel and the opposite locking surface at the upper edge portion of the fourth side edge of a third building panel, in the assembled position.

A set of building panels, wherein each building panel comprises a decorative surface and a mechanical locking device for horizontal and vertical locking of similar or essentially identical building panels in an assembled position by means of a folding and/or vertical displacement, wherein an upper edge portion of a side edge of a first building panel and an upper edge portion of a side edge of a second building panel are, in the assembled position, juxtaposed to form a joint seal, said mechanical locking device comprising:

• a locking strip, projecting outwardly from a lower edge portion of the side edge of the first building panel, comprising a locking element configured to be received in a locking groove arranged in a lower edge portion of the side edge of the second building panel by means of said folding and/or vertical displacement,
• a locking surface at the upper edge portion of the side edge of the first building panel configured to cooperate with a locking surface at the upper edge portion of the side edge of the second building panel, wherein the two locking surfaces are configured to lock the side edge of the first building panel and the side edge of the second building panel in a direction parallel to the extension of the decorative surface,
• a locking surface on the locking element configured to cooperate with a locking surface in the locking groove, wherein the locking surface on the locking element and the locking surface in the locking groove are configured to prevent a displacement between the first and second building panels,
• wherein a first dimension, measured between a point on the locking surface at the upper edge portion of the side edge of the first building panel and a point on the locking surface on the locking element, in an unassembled position, is smaller than a second dimension, measured between the point on the locking surface at the upper edge portion of the side edge of the first building panel and the point on the locking surface of the locking element, in the assembled position.