0001 The present invention relates to a fastener being pressable into a metal sheet in a way safe against rotation and pressing out, having a head or ring the side of which after insertion facing the metal sheet is having radially positioned ridges, which, when setting the fastener, are pressed into the metal sheet, wherein a cylindrical thread-carrier is positioned in the centre of said ridges projecting through the metal sheet beyond the other side of the metal sheet and which in the vicinity of the side of the head or ring facing the metal sheet in the set state is having an annular recess into which the material of the metal sheet displaced during the setting can be pressed. 0002 Such fasteners can be performed as bolts (having a shaft with an exterior thread) as well as nuts (having a through bore with an interior thread). A corresponding fastener for example is known from WO 94/01688. 0003 Similar constructions for example are known from the DE 44 10 475 A1, DE 195 35 537 A1 and WO 98/51934. 0004 In all these known fasteners, the problem is existing that these cannot anymore be used with a thickness of the metal sheet about or below 1 mm or only can be used with a decreased function since the corresponding safety against rotation and pressing out is not given anymore. 0005 Followingly, it is the task to be solved by the present invention to improve such a fastener in such a way that the fastener can be used with metal sheets having a thickness about and even below 1 mm and still achieving the sufficient safety against rotation and pressing out without a special preparation of the opening into which the fastener should be set being necessary. In solutions as e.g. according to DE 44 10 475 A1 or WO 94/01688 around the opening for setting a so-called collar of metal sheet has to be formed to achieve a sufficient safety against rotation and pressing out with thinner metal sheets. This necessitates in a disadvantageous way a further procedural step to form the corresponding collar. 0006 According to the state of art until now one has assumed that an optimal safety of the fastener against rotation and pressing out is achieved if in the vicinity of the thread-carrier as much space as possible is provided to receive the metal sheet material. With thinner metal sheets however not sufficient material of the metal sheet is present to fill such spaces. According to the prior art therefore auxiliary constructions have been used as for example the collar from the WO 94/01688. 0007 Contrary to the above, the present invention starts out from the fact that for achieving an optimal safety against rotation and pressing out with thinner metal sheets not too much space for the displaced material of the metal sheet should be provided but only the volume, which by a deliberate deformation (flowing) of the metal sheet can be filled in an optimal way. This shaping into the annular recess is achieved by a flow shaping of the metal sheet material caused by the special shape of the ridges. 0008 According to the invention, the above task is solved by the features that the ridges over a majority of their radial extension are having a constant height and width and are in the vicinity of the thread-carrier smoothly merging with the same with an increasing width. 0009 By such a construction even with very thin metal sheets, a sufficient safety against rotation and pressing out of the fastener is achieved. 0010 For a further improvement of the safety against rotation according to the invention it is preferred that the ridges are having a basically rectangular cross-section and their side walls are perpendicular to the side of the head facing the metal sheet. By this, the grip of the ridges in the metal sheet material is further improved. 0011 To achieve a close contact of the head on the metal sheet and thereby to avoid the formation of gaps it is useful if the ridges in the radial exterior area are tapering off in a flat manner. 0012 For this purpose, it is of advantage, too, if the ridges in the radial exterior area are tapering off sidewardly in a rounded manner.

0013 In the following, the invention is more detailedly explained on the basis of two exemplary embodiments shown in the drawings. In the drawings show: 0014 FIG. 1 a side view of a fastener as a bolt according to the invention; 0015 FIG. 2 the fastener according to FIG. 1 in a bottom view, wherein the shaft is cut-off in the plane of the annular recess; 0016 FIG. 3 a detailed view of the annular recess and the ridges of the fastener according to FIG. 1; 0017 FIG. 4 a cross-sectional view of one ridge of the fastener according to FIG. 1, wherein the cross-section is across the longitudinal extension of the ridge; 0018 FIG. 5 the fastener according to FIG. 1 shortly before being set in the metal sheet; 0019 FIG. 6 the fastener according to FIG. 1 after setting in the metal sheet; 0020 FIG. 7 a further embodiment according to the invention being performed as a nut, i.e. having an interior thread; 0021 FIG. 8 the fastener according to FIG. 7 in a bottom view (i.e. seen from the side of the metal sheet), and 0022 FIG. 9 the fastener according to FIG. 7 partly in section in the state set in a metal sheet.

0023 FIG. 1 is showing the fastener according to the invention in the form of a bolt, i.e. having a shaft with an exterior thread. The fastener 10 according to the invention is having a head 12 and a shaft 14 carrying an exterior thread. Between the thread and the head 12 in the following order there are provided a calibration collar 16, an annular projection 18 and an annular groove 20 having a generally semi-circular cross-section. On the bottom side of the head 12, which is facing the metal sheet during the setting of the fastener, there are provided radially extending ridges 22, which in their radial extension generally having a constant height and which are tapering off in a flat manner merely in their radial exterior area 21. 0024 The head 12 is shown partly in cross-section, wherein, on the right side, the corresponding ridge 22, too, is shown in cross-section while the corresponding ridge 22 on the left side is shown in front view. 0025 FIG. 2 is showing the head 12 of the fastener of FIG. 1 in a bottom view, wherein the shaft is cut-off in the plane of the annular groove 20. In FIG. 2, the shape of the ridges 22 is especially well shown. The ridges 22 extend in a radial direction with a generally constant width and merely in the radial exterior area 21 near the exterior edge of the screw head 12 are tapering off in their height in a flat manner and are rounded in their width. In the direction of the shaft 14, the ridges 22 in a rounded manner are merging with the annular groove 20. 0026 FIG. 3 is showing a detailed representation of the merger area between the head 12 and the thread-carrier 14. In FIG. 3, the tapering off of the ridge 22 in the exterior area 21 is especially detailedly shown. 0027 FIG. 4 is showing a detail, namely, the cross-section of a ridge 22, the section being across the radial direction of the head 12. In this view, it is extremely well shown how the ridges 22 are shaped in their cross-section. The ridges 22 generally are having a flat rectangular cross-section and are limited by sidewalls 24 generally perpendicular to the level of the head 12. Apart from that the surface of the ridges 22 facing the metal sheet during the setting generally are even and parallel to the plane of the head 12. 0028 FIG. 5 is showing the fastener according to FIG. 1 shortly before the insertion into a metal sheet 100 having a corresponding opening 102. The diameter of the opening 102 is chosen such that the fastener can be inserted with the annular projection 18 just without contact. 0029 In FIG. 6 clearly the indentations 30 are shown caused by the counter tool during the setting. In the same clear way it is shown how the annular groove 20 in the area of a ridge 22 has been filled completely with the displaced material of the metal sheet (right side in FIG. 6) while on the left side in FIG. 6 it is shown that in the area where there is no ridge 22 the annular recess 20 almost completely has been filled with the displaced material of the metal sheet. 0030 The indentations 30 because of the embodiment of the ridges 22 according to the invention and because of the geometry of the annular recess can be performed in such a flat manner that no substantial decrease of the stiffness of the metal sheet even with metal sheets having a very small thickness is occurring. 0031 FIG. 7 is showing a further emobdiment of the invention, wherein in this case the invention has been performed with a fastener serving as a nut, i.e. a fastener having an interior thread. 0032 This further fastener 110 according to the invention is serving as a pressable nut and basically is having a cylindrical shape. In the centre, the fastener is having a broad surrounding ring 112. In a centre of the cylindrical fastener 110 there is a through-bore which at least over a part of the height of the fastener 110 is forming a thread-carrier 114 with an interior thread. Below the surrounding ring 112, the central bore is increased in diameter, which means that in this area only a relatively thin annular surrounding ridge 118 is present. 0033 The fastener 110 according to the invention is meant to be inserted with the ridge 118 first into a hole in a metal sheet 110. On the side of the surrounding ring 112 facing the metal sheet 100 in the set state, i.e. on the underside thereof here, too, there are provided ridges 122 the shape of which being the same as the shape or the ridges 22 in the embodiment according to FIG. 1. 0034 The shape and the position of the ridges 122 can be more clearly described with reference to FIG. 8. This is showing the fastener of FIG. 7 from below. Here, too, the radially extending ridges 122 in their radial direction are having a basically constant width. Merely in the radially exterior area 122 they are rounded in their width and are tapering off in their height. Apart from that the same representation of the cross-section is valid for the ridges 122 as shown for the ridges 22 in FIG. 4. They therefore are having a basically flat surface directed downwardly and being parallel to the level of the ring 112 and sidewalls basically perpendicular thereto. Merely in the direction of the ring 118, i.e. to the interior the ridges 122 in a rounded manner are merging with said ring, which means that they are having a rounded increase of their width in the radially interior area. 0035 The bottom side of the ring 112 in the direction to the interior can be slightly recessed such that in this area the bottom side of the ring 112 not is horizontal but slightly concave. 0036 FIG. 9 is showing the fastener of FIG. 7 in the set state. The fastener 110 is pressed into a hole in the metal sheet 100 having a corresponding diameter. In this connection, the hole in the metal sheet 100 should have a diameter, which makes it possible to insert the fastener 110 with the surrounding ridge 118 just without contact in the hole 102. During the setting, the surrounding ridge 118 by a suitable counter tool is pressed to the exterior whereby the metal sheet is displaced into the edge between the surrounding ridge 118 and the ring 112 and between the corresponding ridges 122. Thereby here, too, a corresponding safety against rotation and pressing out is achieved. In this case, too, the shape of the ridges 122 is of fundamental importance to achieve a complete filling of the space between the surrounding ridge 118 and the ring 112 even when setting the fastener according to the invention in a very thin metal sheet 100.