FR2628799A1 - Insert device screwed into composite materials - threads are at variable angles according to type of composite and slot prevents too high stresses forming - Google Patents

Abstract

The device consists of a cylindrical body (1) with two parallel threads (3, 4) ending in a bevelled edge (9), a slot (7) and a grooved guiding end (10). The angles at the top of the threads (3, 4) vary according to the type of composite material, but are always supplementary angles. The opposite end to the slot can receive a round or a hexagonal collaret (5). As the device is inserted into the composite, the bevelled edge (9) cuts through glass fibres and the material is compressed. The stresses caused by insertion of the device are reduced by the slot (7). USE/ADVANTAGE - Insert screwed into composite materials. The insert, used after moulding, offers comparable performance to existing techniques, plus improved productivity, quality and profitability.

Description

 The present invention relates to steel, brass, zamia or plastic inserts intended to be put in place in supports made of composite materials, to give for example threads, + i 1 stages, axes, spacers; it creates, in particular an insert which is designed to be put in place using a screwing device.

 The present invention develops an insert which, after molding, has performances close to those of the overmolded insert. It thus allows to increase the productivity (no stopping of the press to put the inserts), the profitability (faster amortization). and quality (automatic insertion of inserts).

 In the accompanying drawing, the insert comprises a main cylindrical body carrying two parallel threads ending in a bevel and a slot. The end opposite to the slot can receive a round or hexagonal flange depending on the type of drive. The other can have a grooved pilot end, and can carry in its center either a tapped or smooth hole or a smooth or threaded pin.

 The invention is shown, by way of nonlimiting example +, in the accompanying drawing.

 Fig.1 is a view, partly in elevation, partly in section of the insert opposite its boss.

 In the accompanying drawing, fig.1, the insert comprises a generally cylindrical body designated by (1) having a threaded axial bore (5) and and around its periphery of parallel threads whose angle at the top of one is obtu ( z) and the other acute (4). At one end there is a flange (5) and at the other end a bevel (9) a pilot end (11) with a groove (10) and a slot (8).

 Under operating conditions, the insert must make its way out of fiber-reinforced materials, most often glass. To cut in these glass fibers, a bevel is required fig. as sharp as possible, which is obtained by cutting these threads (3) and (4) along a plane (X X ') perpendicular to the axis of insert <Y Y'). The extreme thinness of the bevel can create a notch which facilitates the attachment and screwing of the first thread of the insert into its support. The pressure to be exerted is then lower and more regular.

 When placing the insert in its hole, it is important that the axis of one (X X ') coincides with: the axis of the other (ZZ) to obtain, on the one hand a regular screwing torque essential for a good installation and on the other hand to avoid that either too high lateral stresses cause the boss (13) to break, or poorly distributed axial forces cause the wall of the hole to tear off ( 12). The pilot tip (ii) is then essential, in particular in the case of manual installation without guide support and also in the case of automatic installation when the variations in the center distance are too large. Its diameter cannot exceed the diameter of the bottom the hole.

 This pilot end has a groove (10) in which the tapping residues can partially accumulate, thus preventing the risks of jamming and consequently the rupture of the boss.

 The insert, after having cut these glass fibers, comes to compress materials which are often rigid, thus inducing increasingly higher stresses as the insert is screwed into its boss. To reduce these constraints, a slot or a groove (7) is milled at least on two threads, thus creating two tapping leprosy, one (8) serving as a roughing and the other (6) for finishing. wide enough and deep enough to allow chip evacuation.

 Depending on the manufacturing process and the nature of the material: very strong or very fragile bosses can be obtained. This is the reason why the threads (3) and (4) are of variable geometry in the sense that their apex angle can vary. while remaining additional For example, when the support material is fragile, the stresses will be reduced as much as possible by using a very sharp thread (25) for attachment and a very obtuse thread (155) which limits the runout by biting slightly in the wall of the hole, thus consolidating the fine thread without creating excessive stresses.

 Conversely, when the material is more resistant, the insert being more stressed, the acute angle will be greater (40) to give a much higher shear strength. The obtuse angle (140) will participate more in the applied loads by penetrating more into the support.

 This double thread in the shape of "W 'makes it possible to absorb the dimensional variations specific to all the assemblies, without causing the rupture of the boss. so that a flat bottom or a rounded rib creates high tensions leading to the rupture of the support.

Claims (7)

 1) Insert characterized in that it comprises a cylindrical body (1)! receiving a double thread (3 and 4) ending in bevel (9), a slot (7) and a pilot end (11) grooved (10).  2) Device according to claim i characterized in that the angles at the top of the threads (3 and 4) are additional.  3) Device according to claims i and 2 characterized in that the angles at the top of the threads (3 and 4) vary according to the nature of the support material while remaining additional.  4) Device according to claims 1,2 and characterized in that lpinterval between two acute threads (4) has the shape of a "w".  5) Device according to claim 1 characterized in that the double thread (3 and 4) ends with a bevel, obtained by a cutting plane perpendicular to the lae of the insert.  6) Device according to claim i characterized in that the slot (7) releases at least two pounds of thread tapping, one for the blank (B), the other for the finish (6)  7) Device according to claim i characterized in that the pilot tip (11) centers and guides the insert in its hole.  e> Device according to claim i characterized in that the pilot tip (11) has a relief groove (10) of the tapping residues.