A female fastening element of this kind is known, for example, from WO 93/15328. This known female fastening element has a housing with a hexagonal outer side and a cylindrical cavity, in which four radially movable segments are disposed around the axial bore for accommodating a male fastening element. Each segment is in the form of a quarter of a cylindrical sleeve provided with an internal screw thread. An elastic ring which holds the four segments pressed under preloading towards the centre of the axial bore lies around the four segments.

The known female fastening element is relatively complex to produce and its cost price is therefore undesirably high, even if, in the case of the known female fastening element, the rotatable cap with which the segments can be pressed outwards in order to disconnect the segments from the male fastening element were to be omitted.

The object of the present invention is to provide a female fastening element which is easy to produce as a mass-produced product at low cost.

The present invention provides a female fastening element according to the preamble of claim 1 which is characterized in that the female fastening element comprises a metal shell body with a shell wall which lies around the axial bore, each segment being integral with the metal shell body and being delimited by an incision in the shell wall of the shell body and being bent towards the centre of the axial bore. A metal shell body of this nature is easy to produce as a mass-produced product.

Further advantageous embodiments of the female fastening element according to the invention are described in the subclaims and in the following description given with reference to the drawing, in which: Fig. 1 shows a preferred embodiment of the female fastening element according to the invention, partially cut

away and in an exploded view, Fig. 2 shows a second exemplary embodiment of the female fastening element according to the invention, Figs. 3a-3d show illustrations of the shell element of a preferred embodiment of the invention, and Figs. 4a-4c show illustrations of the housing of a preferred embodiment of the invention.

Figure 1 shows a female fastening element 10 which is suitable to be pushed onto a male fastening element (not shown) which is provided with an external screw thread without the female fastening element 10 having to rotate with respect to the male fastening element. A male fastening element of this kind usually has a metric screw thread, but the female fastening element according to the invention can also be used with other forms of screw thread or if a thread-like ribbed profile is present on the male fastening element.

The female fastening element 10 is composed of two parts, namely a housing 11 and a shell body 12. In this case, the housing 11 is made of metal and has a circumferential wall 13 which extends from an end wall 14 and, at the edge which is remote from the end wall 14, is provided with a fastening flange 15. The circumferential wall 13 delimits a cavity 16 in the housing 11, which cavity 16 is intended to accommodate the shell body 12.

Preferably, the metal housing 11 is produced by deep- drawing suitable sheet metal, in which case the housing 11 has a less angular shape than that shown in Figure 1. In a variant which is not shown, the housing 11 may be made from a suitable plastic material, for example fibre-reinforced plastic material.

The fastening flange 15, which may also be formed by a plurality of separate lips, projects outwards with respect to the circumferential wall 13, as shown in Figure 1. The metal of which the housing 11 is made is preferably of a readily weldable grade, so that the fastening flange 15 of the housing 11 can be attached to another object via a (spot-) welding operation. In the end wall 14, the housing 11 has an opening 17 which is sufficiently large for a male

fastening element to fit through the opening 17 but not large enough for the shell body 12 which is present in the cavity 16 to leave the cavity 16 via the opening 17. In a variant, the shell body 12 may be locked in position with respect to the housing 11 in some other way. Furthermore, the housing 11 may be provided with openings in the circumferential wall 13.

The circumferential wall 13 forms, on the outer side, a generally known hexagon nut with parallel spanner faces. Since in this case the housing 11 is made from sheet metal, the cavity 16 also has a hexagonal shape.

The shell body 12 has a shell wall which is made from a flat strip of metal, preferably spring steel, which is bent into the hexagonal shell body 12, which shell body encloses an axial bore 18 and fits into the hexagonal cavity 16 in the housing 11, and can no longer move out of the said cavity when the housing 11 has been attached to an object (not described in more detail) by means of its fastening flange 15.

In order to obtain the hexagonal shell wall, the strip of spring steel has six sections, in the drawing numbered 20-25, which, in the circumferential direction of the shell body 12 to be formed, each adjoin an adjacent section in each case via a bend line. A segment 30-35, respectively, which is delimited by a substantially U- shaped incision is formed in each of the sections 20-25, each segment, via a foot which lies on the side of the end wall 14, adjoining the shell wall and being bent inwards about a bend line which lies in the region of the foot.

That free end of each segment 30-35 which is remote from the foot forms an internal screw-thread part, the segments 30-35 being designed and disposed in such a way that together they form two threads of an internal screw thread which is matched to the external screw thread of the male fastening element. To form two threads, the segments 30-35 are alternately arranged at a great and a short distance from that edge of the shell 12 which adjoins the end wall 14 of the housing 11.

In particular, the internal screw-thread part of

each segment 30-35 is formed by that part of the incision which lies opposite to the foot, which part defines a part of an arc of a circle which points towards the foot.

In the installed position, the shell body 12 is enclosed inside the housing 11 and is also locked against rotation with respect to the housing 11 as a result of the complementary shape of the shell body 12 and the inner side of the housing 11.

The segments 30-35 can each move between a radially outer position, in which the male fastening element can be inserted through the opening in the end wall 14 in the female fastening element 10 without a screwing movement of the female fastening element 10 with respect to the male fastening element, and a radially inner position, in which the screw-thread parts are in engagement with the external screw thread on the male fastening element. Obviously, it is also possible to position the shell body 12 the other way round in the housing 11, so that the male fastening element can be inserted into the female fastening element from the side which lies opposite to the end wall 14.

Each segment 30-35 is elastically deformable and, as a result, can move towards the radially outer position as a result of the male fastening element being inserted into the female fastening element 10. The segments 30-35 are designed in such a way that they remain in engagement with the male fastening element of their own accord under a load which seeks to move the male fastening element out of the female fastening element, and in particular the female fastening element 10 is sufficiently robust to withstand the usual safe loading.

Once the female fastening element 10 has been attached to a male fastening element, it can only be unscrewed from the male fastening element by being rotated with respect to the male fastening element. For this reason, the housing 11 forms at least two parallel spanner faces.

In a variant (not shown) to the fastening element 10 which is shown in Figure 1, the flange rim 15 is bent inwards and used to accommodate the shell body 12 in the

housing 11. A fastening element of this nature can be used as a standard nut.

Figure 2 shows a simple female fastening element 40 according to the invention which is suitable to be pushed onto a male fastening element (not shown) which is provided with an external screw thread without the female fastening element 40 having to rotate with respect to the male fastening element.

The female fastening element 40 is formed by a single part and comprises a single metal shell body with a hexagonal shell wall 41. At one end, the axial bore, which is enclosed by the shell wall 41, of the female fastening element 40 is delimited by an end wall 42 in which there is a central opening 43 for the male fastening element (not shown) to project into the axial bore.

The shell body is produced by deep-drawing or the like of sheet metal. If appropriate, an outwardly pro- jecting, encircling fastening flange or separate fastening lips may be provided on the edge which is remote from the end wall 42.

A segment 50-55, respectively, which is delimited by a substantially U-shaped incision is formed in each of the substantially flat sides of the hexagonal shell wall, each segment, via a foot which lies on the side of the end wall 42, adjoining the shell wall and being bent inwards about a bend line which lies in the region of the foot.

That free end of each segment 50-55 which is remote from the foot forms an internal screw-thread part, the segments 50-55 being designed and disposed in such a way that together they form two threads of an internal screw thread which is matched to the external screw thread of the male fastening element. To form two threads, the segments 50-55 are alternately arranged at a great and a short distance from that edge of the shell which adjoins the end wall 42.

The segments 50-55 can each move between a radially outer position, in which the male fastening element can be inserted into the female fastening element 40 through the opening in the end wall 42 without a screwing movement of

the female fastening element 40 with respect to the male fastening element, and a radially inner position, in which the screw-thread parts are in engagement with the external screw thread on the male fastening element.

Once the female fastening element 40 has been pushed onto a male fastening element, it can only be unscrewed from the male fastening element by being rotated with respect to the male fastening element.

It will be clear that the hexagonal shape of the housing which is shown here is advantageous, but not necessary, in order to realize the inventive idea, and that therefore other shapes, for example a cylindrical shape, therefore also fall within the scope of the present invention.

Figures 3a-3d show shell body 60 of a preferred embodiment of the female fastening element according to the invention and Figures 4a-4c show a preferred embodiment of the associated housing 81.

The shell body 60, which is shown in side view in Figure 3b and in plan view in Figure 3c, is made from a flat strip of spring steel which is shown in Figure 3a.

In order to obtain the hexagonal shell wall, the strip of spring steel has six sections, in the drawing numbered 61-66, which, in the circumferential direction of the shell body 60 to be formed, adjoin an adjacent section in each case via a bend line. A segment 67-72, respectively, which is delimited by a substantially U- shaped incision is formed in each of the sections 61-66, each segment, via a foot, adjoining the shell wall and being bent inwards about a bend line which lies in the region of the foot.

That free end of each segment 67-72 which is remote from the foot forms an internal screw-thread part, the segments 67-72 being designed and disposed in such a way that together they form a single thread of an internal screw thread which is matched to the external screw thread of the male fastening element. To form the single thread, the segments 67-72 are arranged at a distance which increases in steps from the bottom free edge of the shell.

The internal screw-thread part of each segment 67- 72 is formed by that part of the incision which lies opposite to the foot and defines part of an arc of a circle which points towards the foot.

The shell body 60 fits into the housing 81, which is yet to be described, and the complementary shape means that it is locked against rotation with respect to the housing 81.

The segments 67-72 are designed in such a way that they remain in engagement with the male fastening element of their own accord and under a load which seeks to move the male fastening element out of the female fastening element, and in particular the female fastening element is sufficiently robust to withstand the usual safe loading.

In order to achieve successful engagement, there is preferably provision for the segments 67-72 to be bent towards the centre of the shell body 60 in the region of their free end, as can be seen in Figure 3d. As a result, it is possible for the free ends of the segments 67-72 to come to bear against the base of the screw thread on the male element.

As a result of the elastic deformability of the segments 67-72, the male element can tilt and move sideways in the female element relatively easily. In order to limit this freedom of movement, there is provision for a second substantially U-shaped incision to be arranged in each section of the shell body 60, so that lips 74-79 are formed. By pressing these lips 74-79 inwards, the space available to the male element is limited without disrupting the action of the segments 67-72. In this case, it is preferable for that part adjoining the foot of each lip 74-79 to be directed inwards substantially at a right angle and for the adjoining part, which runs towards the free end of the lip, to be directed substantially parallel to the shell wall, and advantageously these parts, from the foot, point slightly towards the shell wall, as can be seen in Figure 3d.

Preferably, the feet of the segments 74-79 lie away from the feet of the segments 67-72.

Once the female fastening element has been attached to

a male fastening element, the lips 74-79 limit the freedom of movement, so that tilting and displacement of the elements with respect to one another is counteracted.

In a variant which is not shown, the shell body may comprise two strips, as shown in Figure 3a, which are mirror- inverted with respect to one another. A shell element of this nature, surrounded by a suitable housing, can be used to attach two threaded rods or the like to one another end-to-end.

Figure 4a shows a plan view of the housing 81 when the housing 81 is held in the position shown in Figure 4b. Figure 4c shows a longitudinal section through the housing 81. The housing is of single-part design and is produced by deep- drawing from sheet metal. The housing 81 has a hexagonal circumferential wall 83 which extends from an end wall 84 and is provided, at the edge which is remote from the end wall 84, with two fastening flanges 85 which lie diametrically opposite one another. The flanges 85 can be bent over and attached to another object, for example by welding. The circumferential wall 83 delimits a cavity 86 in the housing 81, which cavity 86 is intended to accommodate the shell body 60.

In the end wall 84, the housing 81 has an opening 87 which is delimited by a circumferential rim 88 which is flanged inwards. This circumferential rim 88 provides the housing 81 with a considerable rigidity and the edge of the shell body 60 fits into the groove between this circumferential rim 88 and the circumferential wall 83.