Gasket with a constant section

Abstract

An annular gasket intended to provide a tight assembly between a first and second pipe after crimping, including an axis of revolution, whereof a section parallel to said axis is a curve formed by a series of an odd number of circle segments C.sub.i connected by apices S.sub.i forming a regular polygon, i varying from 1 to 2*n+1, n being a positive integer greater than or equal to 1, the apex S.sub.i being the center of the circle passing through the apices S.sub.i+n and S.sub.i+n+1 modulo 2*n+1. Such a curve is said to have a constant width. The apices S.sub.i advantageously form a polygon.

Claims

1. An annular gasket intended to provide a tight assembly between a first and second pipe after crimping, including an axis of revolution (X-X), whereof a section parallel to said axis is a curve formed by a series of an odd number of circle segments C.sub.i connected by apices S.sub.i forming a regular polygon, i varying from 1 to 2*n+1, n being a positive integer greater than or equal to 1, the apex S.sub.i being the center of the circle passing through the apices S.sub.i+n and S.sub.i+n+1 modulo 2*n+1.

2. The gasket according to claim 1, wherein the regular polygon is a pentagon.

3. The gasket according to claim 1, which includes a plane of symmetry (P).

4. The gasket according to claim 3, whereof the surface includes an inner portion (SI) facing the axis of revolution (X-X) and an outer portion (SE) opposite the axis of revolution, wherein the inner portion includes the apex S.sub.i found in the plane of symmetry (P).

5. The gasket according to claim 3, whereof the surface includes an inner portion (SI) facing the axis of revolution (X-X) and an outer portion (SE) opposite the axis of revolution, wherein the outer portion includes the apex found in the plane of symmetry (P).

6. The gasket according to claim 3, wherein the bead extends in the plane of symmetry (P) of the gasket.

7. The gasket according to claim 1, which includes, on its surface (S), a bead that extends radially and is made up of portions, said portions being separated by discontinuities forming tailraces before crimping.

8. The gasket according to claim 7, wherein the bead extends from a circle segment (C.sub.i).

9. The gasket according to claim 7, wherein the bead extends from an apex (S.sub.i).

10. The gasket according to claim 7, wherein the height (h) of the bead relative to the surface (S) of the gasket is less than 20% of the diameter of the circumscribed circle at the section of the gasket.

11. The gasket according to claim 7, wherein the bead includes from 2 to 10 portions.

12. The gasket according to claim 7, wherein the height (h) of the bead relative to the surface (S) of the gasket is less than 10% of the radius of the circumscribed circle at the section of the gasket.

Description

DESCRIPTION OF THE DRAWINGS

(1) Embodiments and alternatives will be described below, as non-limiting examples, in reference to the appended drawings, in which

(2) FIG. 1 shows a curve with a constant section (or constant width).

(3) FIGS. 2A and 2B show gaskets whereof the section is a curve with a constant section bearing on a regular pentagon.

(4) FIG. 3 illustrates a gasket placed in a fitting groove to be crimped.

(5) FIG. 4 shows the variation of the compression force based on the movement of a tool for two annular gaskets, a gasket with a circular section and a gasket according to the invention.

(6) FIG. 5 shows the gasket of FIG. 2A also including an interrupted bead.

DETAILED DESCRIPTION

(7) The closed curve 10 of FIG. 1 is built based on the apices S.sub.1 to S.sub.5 of a regular pentagon; one is therefore in the case where n=2. Between the apices, arc of circle segments C.sub.1 to C.sub.5 extend, with radius R. Each apex S.sub.i is the center of the circle segment C.sub.i furthest from the apex S.sub.i on this curve, between the apices S.sub.i+n and S.sub.i+n+1. For example, the segment C.sub.1 opposite the apex S.sub.1 extends between the apices S.sub.3 and S.sub.4. A curve with a constant width refers to a closed planar curve whereof the width, measured by the distance between two opposite parallel straight lines that are tangent to it, is the same irrespective of the orientation of these lines. As illustrated in FIG. 1, in the case of parallel straight lines D1, D1 or D2, D2, one will always pass through an apex S.sub.i and the other will be tangent to the opposite circle segment C.sub.i. As a result, the distance between two such straight lines will always be equal to R, irrespective of their orientation.

(8) The pentagon is inscribed in a circle C with center O and radius r (partially drawn). One can see that the radius R of the segments C.sub.i is significantly larger than the radius r of the circumscribed circle.

(9) FIGS. 2A and 2B illustrate gaskets 100, 200 including an axis of revolution X-X and whereof a section parallel to this axis is a curve similar to that of FIG. 1.

(10) The gaskets illustrated in FIGS. 2A and 2B include a plane of symmetry P.

(11) As illustrated in FIG. 2A, it is possible to define an inner portion SI of the surface S of the gasket 100, turned toward the axis X-X, here including the segments C.sub.2 and C.sub.3, and an outer portion SE of the surface S of the gasket opposite the axis X-X, here including the segments C.sub.1, C.sub.4 and C.sub.5. The apex S.sub.5 is situated in the plane of symmetry P of the gasket 100 and on the inner portion SI of the gasket 100. Conversely, the segment C.sub.5 intersects the plane of symmetry and is situated on the outer portion SE of the gasket. The segment C.sub.5 is provided to be placed in a fitting groove to be crimped. Consequently, the gasket 100 is suitable for insertion through the inside of the gasket.

(12) In the gasket 200 illustrated in FIG. 2B, however, the apex S.sub.5 this time is situated on the outer portion SE of the surface S of the gasket that includes the segments C.sub.2 and C.sub.3, the inner portion SI of the surface S of the gasket including the segments C.sub.1, C.sub.4 and C.sub.5. As before, the segment C.sub.5 is provided to be placed in a fitting groove to be crimped, but this time it is on the inner portion SI of the gasket. Consequently, the gasket 200 is suitable for insertion through the outside of the gasket.

(13) As shown in the context of FIG. 1, the segments C.sub.i have a curve radius R larger than that of a gasket with a circumscribed circular section at the polygon, such that such a gasket 100, 200 is more stable than a gasket with a circular section when a segment C.sub.i is found in the bottom of a groove.

(14) FIG. 3 illustrates this situation: the gasket 100 is found in a gasket groove 300 to be crimped, the segment C.sub.5 being in the bottom of a groove and stabilizing the gasket.

(15) The examination of FIG. 1 also shows that with an identical width, as defined in relation to FIG. 1, such a gasket 100, 200 includes less material than a gasket with a circular section.

(16) Such a gasket will be referred to hereinafter as a pentagonal gasket.

(17) Finite element calculations have been done to compare the behavior of two gaskets made up of a same material (shore hardness: 65 ShA), a gasket with a circular section and a pentagonal gasket, with a same width as defined in relation to FIG. 1. The gaskets are placed in a groove with a substantially square or rectangular section; one wall of this groove forming a tool is mobile and compresses the gasket radially. The force is measured as a function of the movement of the tool.

(18) FIG. 4 is a graph including variation curves of the force in Newtons based on the movement of the tool in mm for such gaskets, curve 50 for the pentagonal gasket and curve 60 for the gasket with a circular section. One can see that the pentagonal gasket better withstands the confinement than the gasket with a circular section: For example, the straight line segment 70 shows that with a movement of the tool of 0.55 mm, there is a corresponding force of about 1000 N for the gasket with a circular section and only about 500 N for the polygonal gasket; The straight line segment 80 shows that a force of 1400 N makes it possible to obtain a movement of about 0.57 mm for the gasket with a circular section and 0.7 mm for the pentagonal gasket.

(19) The pentagonal gasket has a better resistance to confinement, defined as the stress applied by the walls of the groove in the axial direction for the gasket. This case may occur through unfavorable play of the allowances. The pentagonal gasket offers better tolerance. This is a significant advantage relative to the gasket with a circular section. Indeed, upon crimping, the gaskets are mechanically stressed, and if the stress is excessive, there is a risk of total or partial break, and therefore a risk of leak.

(20) FIG. 5 illustrates a cross-section of another embodiment of the gasket 100. In this embodiment, the gasket includes, on its surface 8, a discontinuous bead made up of segments 111 separated by channels 121. As shown in FIG. 5, the bead is found on the inner portion SI of the surface S of the gasket 100 and in the plane of symmetry P of the gasket 100. It rises to a height h above the apex S.sub.1 of the pentagonal gasket. It could, of course, extend from the outer portion SE of the surface S of the gasket and/or from a circle segment C.sub.1 (not shown).

(21) The cross-section of the bead illustrated in FIG. 5 has a lunula shape, i.e., it is defined by a circle with a radius much smaller than the radius R of the circle segments C.sub.i. The height h of the lunula must be sufficient for leaks to occur in the channels 121 before crimping, but not excessive so that the bead segments indeed withdraw by elasticity after crimping. In the illustrated case, the ratio between the height h of the lunula and the diameter (this diameter being equal to 2*r) of the circumscribed circle C at the section of the joint is equal to 0.1/1=10%. More generally, it is established that the ratio h/2*r is preferably comprised between 10% and 20% (to facilitate understanding, the lunula of FIG. 5 is enlarged). For example, in absolute value, for gaskets with a section (or diameter) from 1.50 mm to 5 mm, the height h of the bead may be from 0.10 mm to 0.30 mm.

(22) Embodiments of the invention are not limited by the preceding description. It in particular relates to: Other curve shapes with a constant width, for example based on a triangle (n=1) or a heptagon (n=3), Asymmetrical gaskets, i.e., not having symmetry, Beads that do not extend in the plane of symmetry of the gasket but, for example, in a plane parallel to the plane of symmetry, or that form a helix around the gasket, Bead shapes other than the lunula, for example, a basket handle, or a combination of curves and straight segments, inasmuch as the bead is not continuous.

(23) The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure which are intended to be protected are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure, as claimed.