FR3041395A1 - PLASTIC SLEEVE WITH IMPROVED MECHANICAL STRENGTH - Google Patents

Abstract

A sleeve comprises a body (1) of parallelepipedal section for engaging in a hole with an upper part forming a head (2) for bearing on the hole which is wider than the hole, an intermediate part (4) presenting planar outer surfaces and a lower portion (3) of smaller section than the intermediate portion (4), wherein a cavity (5) is axially formed in the body (5) for receiving a fastener. Slots (6) are arranged on each edge of the body (1) and extend diagonally from the body (1) to the cavity (5), the slots (6) extend from the upper part (2) of the body (1), including transversely on the peripheral edge of the head (1), to at least the mid-section of the intermediate portion (4) of the body (1) forming flexible tabs which widen the cavity (5). ) in a direction perpendicular to the axial direction of the cavity (5) during the axial insertion of the fastener, and at least one retaining catch (7) is arranged on the flat surface between two slit ridges.

Description

TECHNICAL FIELD The invention relates to a sleeve comprising a body of parallelepipedal section intended to engage in a hole with an upper part forming a bearing head on the hole which is wider than the hole, an intermediate part having outer surfaces. planes and a lower portion of smaller section than the intermediate portion, wherein a cavity is formed axially in the body for receiving a fastener.

Prior art

In the automotive industry, to assemble an element to a support, it is known to use an anchor which fits into an opening of a support, then inserting a screw into the perforated element to be fixed on the support. When it comes to a plastic dowel, the tapping is formed by itself during the installation of the screw.

US5593262 discloses a sleeve comprising a body for insertion into an opening of the support and a bearing head on the opening, a part of the body having planar outer surfaces, wherein a cavity is formed in the body for receiving a screw. This sleeve has slots on two opposite flat surfaces, extending axially from the head and over a portion of the body. These slots divide the upper body into two flexible portions that can move elastically toward each other during insertion of the sleeve into the opening. In addition, to hold the sleeve in the holder, retaining notches are present on the other two opposite planar surfaces. Nevertheless, with this arrangement, the slots and the notches being offset by 90 °, the holding of the sleeve in the support during screwing is not optimum.

EP1380758 discloses a sleeve as cited above in which an axially extending slot is provided on each flat outer surface and retaining notches are positioned on two opposite edges of the sleeve. With this arrangement, the sleeve is divided into four portions by the slots which increases the flexibility of the sleeve and the number of points of contact between the head and the flange. The presence of the two retaining notches on two edges of this sleeve makes it possible to increase the resistance of the sleeve in the hole when a tightening torque is applied to the screw. Nevertheless, manufacturers are looking to develop new sleeves to attach an element to a support.

Presentation of the invention

The object of the invention is to provide a sleeve having a better mechanical strength during screwing while being compatible with the constraints of the automotive industry.

More particularly, the subject of the invention is a sleeve comprising a body of parallelepipedal section intended to engage in a hole with an upper part forming a bearing head on the hole which is wider than the hole, an intermediate part having planar outer surfaces and a lower portion of smaller section than the intermediate portion, wherein a cavity is axially formed in the body for receiving a fixation member, characterized in that slots are arranged on each edge of the body and extend diagonally from the body to the cavity, the slits extend from the upper part of the body, including transversely to the peripheral edge of the head, to at least the mid-section of the intermediate part of the body forming flexible tabs which widen the cavity in a direction perpendicular to the axial direction of the cavity during the axial insertion of the fastener, and in e that at least one retaining catch is arranged on the flat surface between two split edges.

The sleeve according to the invention may also have the following features: the retaining catch is an L-shaped abutment projecting from the flat outer surface with a slope oriented towards the lower part of the body; - Two retaining notches are arranged vis-à-vis on opposite outer plane surfaces; - two retaining notches are arranged vis-à-vis at a first height on opposite outer plane surfaces and two retaining notches are arranged vis-a-vis at a second height on the other opposite planar outer surfaces; the cavity which extends in the lower part of the body has a smaller opening than in the rest of the body; -the sleeve is plastic.

With the sleeve according to the invention, it is possible to improve the mechanical strength of a sleeve in a support for assembling an element to a support with a fastening element such as a screw. Indeed, the slots positioned on the edges of the body, arranged diagonally of the head and passing through the head over its entire periphery define four independent flexible tabs, each having an intermediate body portion having a flat outer surface and a head portion of triangular shape at the periphery and circular shape at the sleeve cavity to interfere with threads of the screw. With this arrangement, there are four parts of the heads of the four flexible tabs which block the sleeve on the edge of the hole of the support.

In addition, with this arrangement, each flat outer surface comprises a retaining catch. Thus, maintaining each flexible tab in the hole is improved by the cooperation between the head portion and the retaining catch.

In addition, the retaining notches protruding from the flat outer surface may be positioned at different heights to improve the mechanical strength of the flexible lugs of the sleeve in the hole.

With this arrangement according to the invention, with positioning at different heights of the retaining notches it is also possible to fix the sleeve on supports of different thickness.

Finally, the screw engages with the lower part of the plastic sleeve in which the tapping is formed by itself during the introduction of the screw.

Brief presentation of the drawings

The present invention will be better understood and other advantages will become apparent on reading the description which follows and the appended drawings in which: FIG. 1 is a perspective view of the peg according to the invention; Figure 2 is a top view of the peg according to the invention; Figure 3 is a bottom view of the pin according to the invention.

Description of an embodiment

Figures 1 to 3 illustrate a sleeve according to the invention, for assembling together two elements, or an element to a support, with the aid of a fastener. By way of non-limiting example, in the production of motor vehicle dashboards, holes are formed in panels for receiving sleeves designed for fastening screws, while the sleeves have a cavity for receiving the screws.

The sleeve comprises a body 1 with parallelepipedal section and extends along an axis AA. Here, the body 1 is square section and is made of plastic.

The body 1 comprises an upper part forming a head 2 bearing on the rim of the hole (not shown), a lower part 3 for inserting the sleeve into the hole and an intermediate part 4 with four flat sides, or flat outer surfaces. .

To ensure support, the head 2 is generally flat and extends in a plane perpendicular to the axis AA of the sleeve. The head 2 is wider than the hole.

The lower part 3 has a smaller section than the intermediate part 4.

A cavity 5 is formed axially in the body 1 of the sleeve to receive a fastener. The cavity 5 narrows in the lower part 3 of the body 1.

The body 1 comprises slots 6 which are arranged on each edge of the body 1 and which cross diagonally radially the body 1 to the cavity 5. The slots 6 extend from the upper part of the body 1, including transversely on the peripheral edge of the head 2, to at least the mid-section of the intermediate portion 4 of the body 1. The slots 6 do not extend into the lower part 3 of the body 1.

FIG. 2 illustrates four cross-shaped slots 6 positioned diagonally of the head 2.

The slots 6 thus cut a part of the body into several portions forming here four flexible tabs. As can be seen in FIG. 2, the upper portion has triangular-shaped head portions 2 at the periphery of the body 1 and of circular shape at the cavity 5 of the sleeve. As shown in the figures, the head portions 2 radially project from the flat surfaces of the sleeve body 1.

As shown in Figs. 1 and 3, the planar outer surfaces have a retainer retainer 7 protruding from planar surfaces, the retainer 7 being on the planar surface between two slit ridges. The retaining catch 7 is here an L-shaped abutment projecting from the flat surface with a slope oriented towards the lower part 3 of the body 1.

There may be several retaining notches 7 on the sleeve. Thus, the retaining notches 7 can be positioned at different heights of the flat surface of the intermediate portion 4 of the body 4 as illustrated in FIG.

There may be two retaining notches 7 at the same height facing opposite flat surfaces.

Two retaining notches 7 may be vis-à-vis at a first height on opposite flat surfaces while two retaining notches 7 may be vis-à-vis at a second height on the other opposite flat surfaces.

According to the invention the introduction of the sleeve in the hole is done by the axial engagement of the sleeve in the hole by the lower part 3 of the body 1 and that until the head 2 is supported on the edge of the hole. At the passage of the retaining notches 7 at the orifice of the hole, the flexible tabs approach. Then comes to place an element to be fixed on the hole, the element to fix itself having a hole through which we will pass a screw to engage in the cavity 5 of the body 1. The passage of the screw at the level of the head 2 is facilitated by the central circular shape which interferes with threads of the screw. At the passage of the screw in the intermediate portion 4, the flexible tabs formed by the slots 6 move apart, widening the cavity 5 in a direction perpendicular to the axial direction of the cavity 5.

When screwing the screw, the sleeve is firmly held in the hole by the cooperation of the retaining notches 7 on the flat surfaces of the flexible tabs and the four head portions 2 in contact with the rim of the hole.

When the screw arrives at the lower part 3 of the plastic sleeve, the plastic cavity 5 being narrower, a tapping is formed by itself during the rotation of the screw and thus the screw is engaged in the body 1 sleeve.

Thus, according to the invention, the mechanical strength of the sleeve has been improved in the hole.

The sleeve can be made completely by plastic molding or injection of plastic material to be manufactured at low cost and used to assemble two panels of automotive dashboard for example.

The sleeve could also be made by adding material in a 3D printer if for example it was a small series production.

Claims (5)

Sleeve comprising a body (1) of parallelepipedal section for engaging in a hole with an upper part (2) forming a head (2) for bearing on the hole which is wider than the hole, an intermediate part (4) having flat outer surfaces and a lower portion (3) of smaller section than the intermediate portion (4), wherein a cavity (5) is axially formed in the body (1) for receiving a fastener, characterized in that slits (6) are arranged on each edge of the body (1) and extend diagonally from the body (1) to the cavity (5), the slits (6) extend from the upper part (2) of the body (1), including transversely on the peripheral edge of the head (2), to at least the mid-section of the intermediate portion (4) of the body (1) forming flexible legs which widen the cavity (5) in a direction perpendicular to the axial direction of the cavity (5) during the axial insertion of the fixing element, and in that at least one retaining catch (7) is arranged on the plane surface between two split edges. 2. Sleeve according to claim 1, characterized in that the retaining notch (7) is an L-shaped stop protruding from the flat outer surface with a slope facing the lower part (3) of the body (1). 3. Sleeve according to one of the preceding claims, characterized in that two retaining notches (7) are arranged vis-a-vis on opposite outer plane surfaces. 4. Sleeve according to one of the preceding claims, characterized in that two retaining notches (7) are arranged vis-a-vis at a first height (H1) on opposite outer plane surfaces and two retaining notches (7). ) are arranged opposite one another at a second height (H2) on the other opposite outer planar surfaces 5. Sleeve according to one of the preceding claims, characterized in that the cavity (5) which extends in the lower part (3) of the body (1) has a smaller opening than in the rest of the body (1). .