Fixing device

Abstract: A fixing device having a stem (3) adapted to be retained in a wall, this stem having a shaft (9) carrying flexible non-return blades (13A, 13B, 13C), and having at least three longitudinal wings (10B, 10C) oriented in respective planes which intersect at the central longitudinal axis of the shaft, with the surface defining the free end of each wing being adjacent to the contour provided for the hole when the latter and the said shaft are disposed concentrically.

Description: The invention relates to a fixing device according to the preamble of claim 1, as it is known from FR-A-2 589 204. Fixing devices are already known, generally called marine anchors or Christmas trees, whose stem has a shaft carrying flexible non-return blades each oriented in a plane disposed aslant with respect to the central longitudinal axis of the said shaft, with the connection between the shaft and each elastic blade being oriented transversely to the slope of the blade, and each blade including an end portion which, at rest, extends beyond the predetermined contour of the hole when the latter and the said shaft are disposed concentrically, so that, during the insertion of the fixing device into the hole, the flexible blades make contact with the edge of the latter, flexing so as to be located fully within the contour of the hole, which they can then penetrate, whereas when the fixing device, having been inserted into the hole, is driven in the direction of extraction, flexible blades tend to flex in the direction which causes them to leave the contour of the hole, thereby enabling the fixing device to resist extraction. The invention aims, in general terms, to improve the performance of this type of fixing device, both in terms of its insertion into the hole and in terms of the holding which it affords once it has been put in place. It proposes to this end a fixing device of the above type which is characterized by the features of the second part of claim 1. The ends of the longitudinal wings, which are rigid and can be distributed with respect to each other in a relatively spaced out and regular fashion angularly, thereby guide the shaft with respect to the hole, enabling concentricity between them to be maintained while the stem is being inserted, so that this insertion is much easier and more convenient than with previous fixing devices. Furthermore, during use, cooperation between the end of the different longitudinal wings and the edge of the hole limits the radial clearance of the stem vis-a-vis the hole, thereby improving resistance to extraction, given that holding the shaft concentrically in the hole enables the non-return blades to work under optimum conditions. Furthermore, this limited clearance makes it possible, where the wall is subject to mechanical excitations as occurs in a motor vehicle, to reduce the risk that the fixing device will start vibrating and produce noise nuisances. According to preferred characteristics, at least one said longitudinal wing carries, on at least one side, a series of said flexible blades, disposed parallel and in a stepped fashion. This fashion of placing the series of flexible blades on the shaft, which series enables or enable the fixing device to be used for variable thicknessess, is in fact particularly simple and easy to use, in particular in cases where the fixing device is obtained by moulding a plastic material. According to other preferred characteristics of this embodiment, the said stem has at least two said series of flexible blades, each said series being positioned, along the said central longitudinal axis, with an offset with respect to each other said series. By virtue of this offset, the situation is avoided whereby, during insertion, the blades of different series are simultaneously in the same state of flexion, thereby preventing the force to be exerted to insert the stem into the hole from being very high some of the time (a blade of each series in a state of maximum flexion), and particularly weak at other times (a blade from each series at the start of flexion), and on the contrary results in a relatively regular insertion force, whose maximum value remains moderate. Furthermore, where the stem passes through the wall, and where resistance to extraction is thus produced by flexible blades abutting against the face of the wall opposite the one through which the stem has been inserted into the hole, the offset between the series of wings reduces the axial distance which the stem can travel before the first non-return blade comes into contact with the wall. The fact that the stem is thus able to move only over a relatively limited axial distance before meeting a first resistance to its movement (the maximum resistance is obtained following a larger movement, enabling several blades belonging to different series to come into abutment against the wall) notably offers the advantage of limiting the aforementioned risk that the fixing device will vibrate and produce noise nuisances. It will be observed that, without the offset between the series of flexible blades, it would have been necessary, to obtain similar results, to have a distance between two successive blades in a series, of the same size as this offset, which would have necessitated a multiplication of the number of blades, and therefore increased raw materials, and would also entail, in cases where the fixing device is obtained by moulding a thermoplastic material, serious difficulties in obtaining the mould, since the latter would need to have a particularly thin wall between two hollows to obtain successive blades in a said series. Preferably, for reasons of regularity and ease of production, the said offset, along the said central longitudinal axis, between a said series of flexible blades and each of the other series, is equal to xp/n, where p is the constant distance apart at which the flexible blades of each pair of two successive blades in each series are positioned along the said central longitudinal axis, n is the number of the said series, and x an integer, between 1 and n-1, which is specific to each of the said other series. Thus, if there are for example four series of flexible blades with a distance between two blades of 2.4 mm, the offset between a first series and a second series will be 0.6 mm, the distance between the first series and a second series will be 1.2 mm, and the distance between the first series and a fourth series will be 1.8 mm. According to other preferred characteristics, the fixing device has exactly four said longitudinal wings. The shaft thus has a cross-shaped transverse section, a shape which affords an excellent ratio between the quantity of raw material needed and the quality of guidance provided vis-a-vis the hole. According to other preferred characteristics, the fixing device has exactly four said longitudinal wings, with two wings which each carry, on two opposite sides, a said series of flexible blades, the two other wings carrying no flexible blade. This shaping of the shaft and this arrangement of flexible blades affords excellent results, in an eminently simple, convenient and economical fashion. According to other preferred characteristics, each said flexible blade is carried by a said longitudinal wing, with a connection which is oriented according to the slope of the blade. Thus, unlike the aforementioned prior fixing devices, each flexible blade, during the insertion of the stem, gradually comes into contact with the edge of the hole, by virtue of which the force to be exerted on the fixing device to insert the stem into the hole remains moderate. According to other preferred characteristics, each said flexible blade is inclined so that, during its insertion into the said hole, the area of contact with the edge of the said hole progressively approaches the wing which carries this blade. Thus the area of the flexible blade which is forced first to resist the extraction of the stem is located near the wing which carries this blade, so that this area is relatively inflexible, and therefore provides high-quality holding. According to other characteristics, preferred as being favourable to the regularity of the force to be exerted to sink the stem into the hole, the said end portion of each said flexible blade which, at rest, extends beyond the said predetermined contour, is crescent-shaped. According to other preferred characteristics, notably for reasons of ease of use, the said stem is connected, at one end, to a head, and has, at the other end, a conical tip centred on the said longitudinal central axis. The disclosure of the invention will now continue with the description of an example embodiment, given hereinafter by way of non-limitative illustration in relation to the accompanying drawings, in which: Figures 1 and 2 are respectively a perspective view and an elevation view of a fixing device in accordance with the invention; Figure 3 is a view in cross section taken along the plane shown at III-III in Figure 2; Figure 4 is a partial, highly diagrammatic elevation view of this fixing device positioned in a respective hole of an object and of a support which it holds with respect to each other, this object and this support being shown in cross section; and Figure 5 is a view similar to Figure 4, but showing how the fixing device resists extraction when the object and the support tend to move away from each other. The fixing device 1 illustrated in the drawings is obtained by moulding a thermoplastic material. It has a head 2 and a stem 3 provided, at the end opposite that by which it is connected to the head 2, with a conical tip 4, the stem 3 and the head 2 having a common longitudinal central axis 5. The head 2 has a well-known shape, with a concave lower face 6 which extends radially projecting with respect to the shaft 3. The tip 4, whose end 7 is rounded, enables the stem 3 to be easily centred in a well known manner with respect to the hole into which it is to be pushed, the base 8 of the tip 4 having the same contour as the hole into which it is envisaged that the stem 3 will be inserted. The latter has, between the base 8 of the tip 4 and the head 2, a shaft 9 having four longitudinal wings 10A to 10D, the wings 10A and 10C being oriented in a plane 11A while the wings 10B and 10D are oriented in a plane 11B, the planes 11A and 11B being perpendicular, and intersecting at the axis 5. The respective surfaces 12A to 12D which delimit the free end of each of the wings are exactly overhanging the contour of the base 8, as can be seen more particularly in Figure 3, that is to say the surfaces 12A to 12D are adjacent to the predetermined contour for the hole in which the stem 3 needs to be inserted, when this contour and the shaft 9 are disposed concentrically, the contour provided here for the hole being circular. The wings 10B and 10D each carry, on two opposite sides, a series of flexible non-return blades, respectively 13A to 13D. The series of flexible non-return blades 13B will now be described more particularly, it being understood that the series of blades 13A, the series of blades 13C and the series of blades 13D are identical. The blades 13B, which number six in this case, are disposed in parallel and in a stepped fashion, with a constant separation p (Figure 2) along the axis 5, which is for example 2.4 mm. Each of the blades 13B is substantially plane and oriented in a plane disposed aslant with respect to the axis 5, the inclination being such that the plane in which the blade 13B is oriented approaches the tip 4 at the same time as it approaches the axis 5. As can be seen in Figure 3, each blade 13B has at rest, that is to say in the position shown in Figures 1 to 3, which it takes spontaneously, an end portion 14, in this case crescent-shaped, which extends beyond the contour of the base 8, that is to say beyond the predetermined contour of the hole in which it is envisaged that the stem 3 will be inserted, when the shaft is disposed concentrically with respect to it. It will be observed that each blade 13B, by virtue of the fact that it is connected to the wing 10B which carries it at its slope, will make contact only gradually with the edge of the hole in which the stem 3 is to be inserted, and that, given its inclination, the area of contact with the edge of the hole will first be situated in the vicinity of the wing 10C, and will then gradually approach the wing 10B which carries the blade 13B. As can be seen in Figures 1 and 2, each series of flexible blades is positioned, along the axis 5, with an offset with respect to each other series. More precisely, the series of blades 13B has with respect to the series of blades 13A an offset e (Figure 2) towards the tip 4, the series of blades 13D having the same offset e, in the same direction, with respect to the series of blades 13A, and similarly for the series of blades 13C with respect to the series 13D. In the example illustrated, the offset e is equal to one quarter of the distance p between two successive blades in any of the series of blades, so that there is also an offset e between the first blade 13C as from the head 2 and the second blade 13B as from the head 2, and more generally between the n-th blade 13C as from the head 2 and the n+1-th blade 13B as from this head. It will be observed that the end surfaces 12A and 12C of the wings 10A and 10C, which carry no flexible blade, are rounded with a much smaller radius than that of the base 8, while the surfaces 12B and 12D are rounded according to the latter radius, so that the wings 10A and 10C make contact with the edge of the hole over a relatively linear area, while the wings 10B and 10D make contact with a wider area. The faces of the wings 10B and 10D which carry the flexible blades are in the shape of a highly open concave dihedron, with an angle substantially equal to 165°, which enables the projection of the flexible blades to be adjusted, and therefore enables their ability to flex to be adjusted. The ends of the flexible blades facing the outside are shaped in such a way that the surfaces delimiting these ends are parallel to the axis 5. With the aid of Figures 4 and 5 an example of use of the device 1 will now be described which consists of holding the object 15 on a support 16, this support and this object each having a thin wall in which is formed a circular hole of the same diameter as the base 8 of the tip 4, the sum of the thicknesses of these walls being approximately equal to the distance separating the head 2 from the blade 13B which is the closest thereto. The stem 3 is firstly inserted into the hole in the object 15, with respect to which it is presented with the tip 4 first, which enables the stem to be centred with respect to the hole, which is effected when the base 8 is located therein, the foot being pushed in by then exerting a force, for example with the thumb, on the head 2. The flexible blade closest to the head 2, which is one of the blades 13C, then makes contact with the edge of the hole, and begins to flex in order to be able to pass through the hole, the following blades, which are respectively a blade 13D, a blade 13A and a blade 13B, begin to cooperate in a similar fashion with the edge of the hole, the different blades of the stem 3 each flexing in turn to be able to pass into the hole. The insertion of the device 1 into the hole of the support 16 takes place in exactly the same fashion, once the object 15 has been inserted into the hole, or at the same time, with the respective holes superimposed. When the device 1 has been inserted into the two holes (Figure 4), the face 6 of the head 2 bears against the object 15 while the upper faces of the blades 13A to 13D which are closest to the head 2 have at least part of their portion 14 opposite the object 16. It will be observed that the surfaces 12A to 12C have afforded, during the insertion of the device 1, guidance against the edge of the holes, which facilitated this insertion, and that in the position in Figure 4 these surfaces limit the radial clearance of the device 1 with respect to the object 15 and support 16, and more generally afford excellent mutual holding between the device 1, the object 15 and the support 16. The axial clearance of the assembly of the latter is determined by the difference between the sum of the thicknesses of the abutted walls of the object 15 and support 16, and the distance separating the flexible blade closest to the head 2, which is a blade 13B, from this head, the clearance being limited on the one hand by the head 2 coming into contact with the object 15, and on the other hand by the part of this blade 13B coming into contact with the support 16. When a significant extraction force is exerted on the device 1, for example in the case whereby the object 15 tends to move away from the support 16 as shown in Figure 5, the blade 13B, which makes contact first with the support 16, flexes sufficiently for a blade 13A to come in turn against the support 16 and, depending on the magnitude of the extraction force, there may even be a set of blades 13A to 13D bearing on the support 16 to resist extraction. It will be noted that, by virtue of the arrangement just described, the device 1 can be inserted into the hole in one or more thin walls, with a relatively even force whose maximum intensity remains moderate, and in any case considerably weaker than the force needed to extract the device 1 from the hole into which it has been inserted. It will be observed that, in the example of use illustrated in Figures 4 and 5, only the flexible blades closest to the head 2 are useful for preventing the device 1 from being extracted. It is, however, advantageous to have provided series of at least two flexible blades disposed in a stepped fashion, given the major variations in size which the object 15 and the support 16 may exhibit, given that the walls seen in Figures 4 and 5 consist of a metal sheet with a hole formed by punching. It will be observed that in another use of the device 1, the hole in the object 15 can be larger than the one in the support 16, so long as the hole in 15 has a diameter smaller than that of the head 2. In yet another use, the stem 3 is inserted in a hole in a thick wall through which it does not pass. Numerous variants are possible depending on the circumstances. Thus, in variants not depicted, each series of blades 13A to 13D is formed only by two distinct blades; the shaft 9 is replaced by a shaft having only three arms, or by a shaft having more than four arms, the different arms being regularly distributed angularly, that is to say, in cases whereby there are three arms, each arm is spaced apart from neighbouring arms by 120° and, in cases whereby there are five arms, by 72°; the number of series of flexible blades carried by the shaft is fewer than four, for example a single series, or greater than four; the flexible blades are located on the shaft in a different manner, for example each wing carries a series of flexible blades on a single side, or the connection between each flexible wing and the wing which carries it is oriented transversely to the slope of the blade; the contour of the hole into which the fixing device is to be pushed is not circular in shape, for example it is oval; the head 2 is replaced by a different head, for example provided with a fixing means for an object to be fixed to the wall in which the stem of the fixing device must be inserted, or the stem 3 is integrated directly into the object to be fixed, or the head 2 is eliminated, and a recess formed in the shaft to receive a screw for example. It should be stated that the invention is not limited to the examples described and depicted.

Claims: Fixing device having a stem (3) adapted to be retained in a rigid wall (16) after it has been inserted into a hole with a predetermined contour in this wall, said stem having a shaft (9) carrying flexible non-return blades (13A-13D) each oriented in a plane disposed aslant with respect to the central axis (5) of said shaft, each said flexible blade having, at rest, an end portion extending beyond said predetermined contour when said hole and said shaft are disposed concentrically, whereby said shaft (9) has, at the level where it carries said blades (13A-13D), at least three longitudinal wings (10A-10D) oriented in respective planes (11A, 11B) which intersect along said central longitudinal axis (5), each said wing (10A-10D) being delimited by opposites sides and by a free end characterised in that the respective free end of each wing (10A-10D) extends in parallel to said central longitudinal axis (5) at a constant radial extension which enables a respective surface (12A-12D) defining said free end of each said wing (10A-10D) to make contact with said predetermined contour when said hole and said shaft are disposed concentrically. Device according to Claim 1, characterised in that at least one said longitudinal wing (10B, 10D) carries, on at least one side, a series of said flexible blades (13A-13D), disposed parallel and in a stepped fashion. Device according to Claim 2, characterised in that the said stem (3) has at least two said series of flexible blades (13A-13D), each said series being positioned, along the said central longitudinal axis (5), with an offset with respect to each of the other said series. Device according to Claim 3, characterised in that the said offset, along the said central longitudinal shaft (5), between a said series of flexible blades and each of the other series, is equal to xp/n, where p is the constant distance apart at which the flexible blades of each pair of two successive blades in each series are positioned along the said central longitudinal axis (5), n is the number of the said series, and x an integer, between 1 and n-1, which is specific for each of the said other series. Device according to any one of Claims 1 to 4, characterised in that it has exactly four said longitudinal wings (10A-10D). Device according to any one of Claims 2 to 4, characterised in that it has exactly four said longitudinal wings (10A-10D), with two wings (10B, 10D) which each carry, on two opposite sides, a said series of flexible blades (13A-13D), the other two wings (10A, 10C) carrying no flexible blade. Device according to any one of Claims 1 to 6, characterised in that each said flexible blade (13A-13D) is carried by a said longitudinal wing (10B, 10D), with a connection which is oriented according to the slope of the blade. Device according to Claim 7, characterised in that each said flexible blade (13A-13D) is inclined so that, during its insertion into the said hole, the area of contact with the edge of the said hole progressively approaches the wing (10B, 10D) which carries this blade. Device according to any one of Claims 1 to 8, characterised in that the said end portion (14) of each said flexible blade which, at rest, extends beyond the said predetermined contour, is crescent-shaped. Device according to any one of Claims 1 to 9, characterised in that the said stem (3) is connected, at one end, to a head (2), and has, at the other end, a conical tip (4) centred on the said longitudinal central axis (5).

Inventors: COURTIN CHRISTIAN, COURTIN, CHRISTIAN
Applicants: ITW DE FRANCE, I.T.W. DE FRANCE
Application year: 1996
Main classification: F16B19
IPC codes: F16B19, F16B21