METALLIC HOLDING ELEMENT FOR INTRODUCING A TORQUE INTO A PLASTIC HOUSING

Abstract

A metallic holding element for absorbing or introducing a torque in a plastic housing is presented, wherein the holding element in the holding area features a profile with three, four, or five main corners, which are connected to each other via straight or convex edges, preferably the edges are generally curved in a convex manner respectively through one or more obtuse-angled intermediate corners.

Claims

1. A metallic holding element for pressing into an opening of a plastic housing and absorbing or introducing a torque in the plastic housing, wherein the holding element includes a holding area free from concave incisions, indentations, or undercuts, and in its profile form includes three, four, or five main corners, which are connected to each other via straight or convex edges, wherein the holding element further includes: a) a cylindrical bore hole with a specified lower dimension for holding a self-tapping screw, b) an inner thread, or c) a tap with an outer thread connected to the holding element.

2. The metallic holding element according to claim 1, wherein the holding element includes in its profile form three main corners, wherein the edges are respectively curved in a concave manner through one or more obtuse-angled intermediate corners.

3. The metallic holding element according to claim 1, wherein the holding element is produced from a lead-free, metallic material and using cold-formed mass forming.

4. The metallic holding element according to any one of the preceding claims, characterized in that the main corners are rounded off, wherein preferably the rounded off area of the main corner is maximum 25% of the length of the edge between the main corners.

5. The metallic holding element according to claim 1, wherein in the direction of a middle axis, the holding element includes on one side an insertion area with an outer circumference which tapers inwards towards the middle axis.

6. The metallic holding element according to claim 1, wherein the direction of the middle axis, the holding element includes on one side an edge area with an edge running outwards from the middle axis, the outer circumference of which is larger than in the holding area.

7. A holding assembly comprising: a plastic housing defining an opening; a metallic holding element for pressing into the opening of the plastic housing and absorbing or introducing a torque in the plastic housing, wherein the metallic holding element includes a holding area free from concave incisions, indentations, or undercuts, and in its profile form includes three, four, or five main corners, which are connected to each other via straight or convex edges, wherein the metallic holding element further includes: a) a cylindrical bore hole with a specified lower dimension for holding a self-tapping screw, b) an inner thread, or c) a tap with an outer thread connected to the holding area.

8. The holding assembly according to claim 7 wherein the opening of the plastic housing is cylindrical before the pressing-in of the holding element.

9. The holding assembly according to claim 7, wherein the opening of the plastic housing includes a surface profile size near the holding area of the metallic holding element after the pressing-in of the metallic holding element which is maximum 7% larger than the surface profile size of the press-in opening before the pressing-in of the metallic holding element.

10. The holding assembly according to claim 9, wherein the opening of the plastic housing includes a surface profile size near the holding area of the metallic holding element after the pressing-in of the metallic holding element which is maximum 3.5% larger than the surface profile size of the press-in opening before the pressing-in of the metallic holding element.

11. The holding assembly according to claim 7, wherein the opening of the plastic housing is arranged as a plastic dome.

12. The holding assembly according to claim 11, wherein the surface profile size of the opening of the plastic housing defines a surface profile size before pressing-in which corresponds to between 25 and 60% of the surface profile size of the plastic dome.

13. The holding assembly according to claim 7, wherein the holding area features a length in the direction of a middle axis which is less than a corresponding length of the provided opening in the plastic housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other advantages of the disclosed subject matter will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

[0035] FIGS. 1a and 1b show profile views through a holding element according to one exemplary embodiment;

[0036] FIG. 2a shows a plastic housing before installation of the holding element according to one exemplary embodiment;

[0037] FIG. 2b shows the plastic housing with the holding element installed according to one exemplary embodiment;

[0038] FIG. 2c shows the plastic housing with the holding element removed according to one exemplary embodiment;

[0039] FIG. 3 shows the holding element and the plastic housing with three main corners according to one exemplary embodiment;

[0040] FIG. 4 shows the holding element and plastic housing with four main corners according to one exemplary embodiment;

[0041] FIG. 5 shows a holding element and plastic housing with five main corners according to one exemplary embodiment;

[0042] FIGS. 6a-6c show different edge forms and the sizes that may occur;

[0043] FIG. 7 shows a profile through a mounting area of the plastic housing with installed holding element according to one exemplary embodiment; and

[0044] FIG. 8 shows a holding element with a molded-on bolt according to one exemplary embodiment.

DETAILED DESCRIPTION

[0045] FIG. 1a shows an exemplary embodiment of the holding element with a longitudinal section along a middle axis X. The holding element 1 includes a holding area 111. In this exemplary embodiment, an edge area 116 with a circumferential edge 16 connected to the holding area 111, on what is here the upper side.

[0046] This circumferential edge 16 can, on the one hand, serve as a stop when the holding element is pressed into a corresponding opening of a plastic housing. On the other hand, this edge 16 can serve to lay on an enlarged support surface, for example, a circuit board 4 or a base plate 5 as shown in FIG. 7, for affixing a housing part over an accordingly large area. The size and form of the edge 16 is generally freely selectable and can, for example, be kept as a circle, and does not need to feature the main corners 11 of the holding area 111 as will be discussed in greater detail further below.

[0047] On the lower side shown in FIG. 1a, in the direction of the middle axis X, the holding element 1 includes an insertion area 115 with a tapering outer circumference inclining inwards towards the middle axis X with a recognisable slope 15. This insertion area 115 on the press-in side serves to provide simple insertion into the press-in opening of the plastic housing. In contrast to the outer circumference form of the holding element 1 in the holding area 111 discussed in greater detail below, the insertion area 115 can taper through to a circular outer circumference.

[0048] FIG. 1b shows the profile already indicated in FIG. 1a through the holding area 111, on which here precisely three main corners 11 are provided which are connected to each other via edges 12.

[0049] FIG. 1b sketches an exemplary embodiment of the edges 12, namely with two obtuse-angled intermediate corners 14, so that the overall form of the edges curves slightly outwards, i.e. in a convex manner. However, it should expressly be noted that in general, straight edges or other convex edge forms, or for example only one obtuse-angled intermediate corner 14, are possible. Due to the disadvantages of production technology, in this holding area 111, however, precisely no incisions or even undercuts are provided in the direction of the middle axis X. The special shape of the edges is discussed in greater detail below in connection with FIG. 6.

[0050] The possible alternative number of main corners 11 is also discussed in greater detail below with reference to FIGS. 3, 4, and 5.

[0051] Another exemplary embodiment of the plastic housing 2 will be explained with reference to FIGS. 2a to 2c. FIG. 2a shows a top view onto a so-called plastic dome, i.e., a hollow cylindrical body essentially protruding from the plastic housing, which is shown, for example, in FIG. 7 in profile.

[0052] This plastic form 22 defines an opening 21 which includes a circular form and at least, in a corresponding area in the holding area 11 of the holding element 1, a diameter D21. On the lower end of the plastic dome 22, in relation to FIG. 7, the opening can also be formed for a narrow and additional edge 25, which lies so deep in the insertion direction, however, that the holding element 1 can be fully inserted with its holding area 111.

[0053] The plastic dome 22 includes an outer diameter D22 and, accordingly, the wall thickness of the dome is (D22−D21)/2. The inner diameter D21 of the dome 22 is here smaller than the corner size 112 sketched in FIG. 1b between the main corner 11 and the respective opposite edge 12 by a specified amount, so that a press-fit of the holding element 1 occurs, wherein the plastic material on the edge of the opening 21 is pressed not only in the press-in direction, but also in the wall areas of the opening 21, located on the side of the main corners 11. As a result, the stress of the plastic dome 22 is, on the one hand, less than when a round bolt is pressed in with a diameter that corresponds to the corner size 112, while on the other hand, however, as a result of this plastic material which engages behind the main corners 22, improved firmness is provided precisely with regard to torque stresses.

[0054] The press-in opening 21 features a surface profile size in the holding area after the holding element is pressed in which is a maximum 7% larger than the surface profile size of the press-in opening 21 before pressing in, and preferably less than 3.5% larger. Thus, it is possible that the surface profile size of the press-in opening 21 corresponds before pressing in to between 25 and 60% of the surface profile size of the plastic dome 2, i.e., a relatively large holding element can be used in relation to the surface profile size of the plastic dome, without the risk occurring that the walls of the plastic dome might crack.

[0055] FIG. 2b shows a section through the plastic dome 22 with the pressed-in holding element 1. In order to better clarify the effect of the holding element 1 during pressing in and the deformation of the opening 21, in FIG. 2c, a superficial insight is shown into the opening 21, in which the holding element 1 has again been removed. Here, those areas 221 can clearly be seen in which the main corners 11 have cut themselves into the wall of the opening 21, as well as the areas 222 in which material that has accordingly been displaced has also built up, so that there the lower edge 25 can even be partially covered over.

[0056] FIG. 3 now again shows the embodiment already described in FIGS. 1 and 2, with three main corners 11 and the intermediate corners.

[0057] By contrast, FIG. 4 shows a further exemplary embodiment with in this case four main corners 11, which are also rounded off, but which are otherwise connected with straight edges 12.

[0058] FIG. 5 also superficially shows a further exemplary embodiment, here with 5 main corners, which are arranged offset from each other by 72° respectively in the form of a regular pentagon, and which are in turn rounded off, wherein here, too, the edges 12 which lie opposite the main corners 11 respectively are respectively also straight.

[0059] In all cases, the main corners 11 respectively ensure a corresponding incision in the edge area of the opening 21 in the plastic housing, and a corresponding displacement of material into the adjacent wall areas. If, however, one were to further increase the number of main corners 11 to above five, the outer circumference form that is created becomes increasingly circular and the form of the main corners 11 in the accessible wall areas become even smaller, so that the key inventive effect is still only insufficient, and thus a number of main corners greater than five appears to be unsuitable.

[0060] FIGS. 6a to 6c now, with references to examples with three main corners respectively, sketch the particular influence of the design of the edges for the respective critical minimum thicknesses of the holding element on the one hand, while on the other also for the plastic housing, in particular the plastic dome.

[0061] Assuming a uniform inner diameter D13 for all three examples, and a uniform theoretical circular diameter over the main corners D33, a significantly lower minimum wall thickness of the holding element D123 results. In order to achieve sufficient rigidity of the holding element, a minimum wall thickness must be provided.

[0062] If one considers that the opening 13 creates a bore hole for holding a self-tapping screw 3 or is equipped with an inner thread and serves to screw in a screw 3, it becomes clear that a corresponding mechanical stress lies on this wall thickness D123. The diameter results from the given inner diameter D13 and minimum wall thickness D123. With variant A, this must be considerably larger than with B and C. As a result, the plastic dome must also be correspondingly larger.

[0063] In FIG. 6b, three main corners 11 are connected via edges 12, which respectively feature two obtuse-angled intermediate corners 14 and straight intermediate sections 124, so that the overall forms of the edges 12 are curved in a convex manner in each case. The intermediate corners 14 are here preferably arranged at a respectively identical distance from the main corners 11, wherein instead of the two intermediate corners 14 shown here in FIG. 6b, an embodiment with just one intermediate corner or even three intermediate corners would be feasible, wherein the intermediate corners 14 are respectively more obtuse-angled than the main corners 11.

[0064] By contrast, FIG. 6c shows an edge 122 that curves continuously outwards in a convex manner, which also enables a larger minimum wall thickness D123c>D123a than the straight edge 121 in FIG. 6a.

[0065] FIG. 7 illustrates a cross-section through the affixing area of a housing of an electronic assembly, including a plastic housing part 2 with a plastic dome 22, in which a metallic holding element 1 according to the invention has been pressed in. The housing is closed on the opposite side by the second housing part 5, wherein said housing part can for example also be metallic. These two housing parts 2 and 5 are connected to each other via a screw 3, which is screwed into the holding element 1. Between the second housing part 5 and the first housing part 2 or the edge 16 of the holding element 1, a circuit board 4 with electronic components is also provided, and also affixed there. As an alternative to this embodiment with a screw 3, affixation via rivets is also feasible. The holding element 1 is free of undercuts in the holding area 111 and has a length in the axis direction X which is shorter than the length of the opening in the plastic dome 22.

[0066] FIG. 8, by contrast, sketches a further embodiment with a tap 17 connected to the holding element 1 with an outer thread, wherein the affixing area 111 of the holding element 1 in turn features a profile form as described in greater detail above. This embodiment, too, is suitable for providing that the holding element 1 is produced from a lead-free, metallic material and using cold-formed mass forming.

[0067] The present invention has been described herein in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims.