FR2497907A1 - Annular dynamic composite seal - has inner seal material surrounded and protected by outer resilient material - Google Patents

Abstract

The seal ensures dynamic sealing between a piston and a cylinder or a guide and a piston shaft separating two enclosures in which there are different pressures. An annular element (1) comes into contact with the fluid and with the rigid surfaces, completely encloses an insert (2) and is made of plastics having good resistance to friction, extrusion and chemical attack. The seal insert material (2) is chosen for its residual elasticity and may be circular, elliptical or trapezoidal in section.

Description

 The present invention relates to an annular seal. It relates more particularly, although not exclusively, to the production of seals which ensure dynamic sealing between a piston and a cylinder, or between a rod guide and a sliding piston rod in this guide, and which separate two enclosures in which reign different pressures.

 Seals of this kind are commonly made up of various Juxtapo6és annular elements, produced in distinct materials having properties adapted to the functions which each of the constituent elements must fulfill. These elements are either independent pieces simply joined together, or elements molded together or glued to each other, in which case their union gives “One-piece” composite seals.

In all cases, the fluid to be sealed is in contact with each of the constituent elements of the seal, which all appear on the surface of the seal.

This current design has drawbacks, particularly in the case of seals comprising an annular element called "stuffing" made of a first material whose mechanical characteristics are used to press an active element, provided with at least a sealing and / or scraping lip, made of a second material chosen for its friction characteristics and resistance to extrusion, as well as for its properties of resistance to chemical attack by the fluid to be sealed. packing must, as far as possible, be made of a material of the rubber type, having a very good "elastic remanence n C", that is to say regaining its initial dimensions after compression; such a material generally has a low hard tee, hence a risk of extrusion by mechanical parts or parts in contact with the joint, in particular moving parts or parts relative to the joint. Furthermore, the resistance of this kind of material chemical attack can only be obtained at the cost of an increase in the manufacturing cost and, often, a reduction in its mainly sought-after mechanical qualities
The present invention aims to remedy these drawbacks, by providing a different joint structure, in which the element such as stuffing is no longer in contact with the fluid to be sealed or with xechanical parts or parts.

To this end, the subject of the invention is essentially an annular seal, in which an annular element produced in a first surface, and intended to come into contact with the fluid to be sealed and with rigid surfaces, fixed or mobile, between which the joint must seal *, completely encloses at least one other annular element, made of a second material chosen for its mechanical characteristics
The first annular element, constituting the external part of the joint, is preferably made of a material, such as polyurethane, polyamide, polyolefin or polyester elastomer, having good resistance to friction, to extrusion and to the chemical attack of the fluid to be sealed, but which may have lower qualities of elastic persistence, which are compensated for by the choice of the material of the internal element, which can be produced, for example, in natural rubber, inexpensive and whose mechanical characteristics are exceptional. as the last element is completely embedded inside the first, there is no longer any need to worry about its resistance to friction or to extrusion, or its resistance to chemical attack.

The seal according to the invention thus benefits from the advantageous characteristics of the materials of its two elements, without having the disadvantages.
The internal element may be a torsion, or an annular element of elliptical, oblong, rectangular, trapezoidal or other polyonal section. In the case of a joint having a large axial dimension, related to its thickness, two or more elements internal can be embedded in the same external element, and suitably distributed over the entire length of the joint.

 Finally, the actual design of the seal that is the subject of the invention solves the question of assembling the various components of the seal into a one-piece structure. However, it is not excluded to add an additional element, such as an extrusion, on a base joint formed by two elements, one of which is embedded in the other.

In any case, the invention will be clearly understood with the aid of the description which follows, with reference to the appended schematic drawing showing, by way of non-limiting examples, some embodiments of this annular seal.
Figure 1 is a view, in half section, of a single-acting seal according to the invention, of very simple shape;
Figure 2 is a view, in half-sections of another single-acting seal according to the invention, of more complex shape;
Figures 3 and 4 are views, in half-section, showing still two other single-acting seals according to the invention, of considerable length;
Figures 5 to 8 are views, in half-section, of various double-effect seals, tealisEs according to the invention, with internal elements of various shapes.

 In FIG. 1 is shown a single-effect annular sealing gasket, composed of an external annular element 1 made of a first material, and an internal annular element 2 made of a second material.

 The external element 1, which comes into contact with the fluid to be sealed and with the surfaces between which the seal must seal, comprises on its outside face a static sealing area 3, and on its inside face a book of 'dynamic seal 4. Given the functions it provides, the external element 1 is advantageously made of polyurethane, polyamide, polyolefin or polyester elastomer. The heel 5 of this external element 1 can carry an anti-extrusion ring 6, made in particular of acetal resin.

 As for the internal element 2, entirely embedded in the external element 1, it here has a toroidal shape, and can be produced in particular from natural rubber, or from an elastomer based on natural or synthetic rubber. This internal element 2 plays the role of stuffing, elastically pressing the static sealing zone 3 and the dynamic sealing lip 4 of the external element 1 against the corresponding rigid surfaces, fixed or mobile, and ensuring a distribution of the pressures.

 FIG. 2 represents a single-effect seal, produced according to the * th principle but of more complex shape. The external element 1 comprises, as previously on its external face, a static sealing zone 4, while on its internal face are formed two filiform lips 7 for wiping, as well as a lip 8 for scraping the impurities. tees, with extended contact 9 for resistance to wear. The internal element 2 is either toroidal, or of elliptical section as indicated in dotted lines.

 FIGS. 3 and 4 show two other single-acting sealing joints, the inner face of which comprises multiple books 10, these joints having a large axial dimension, relatively to their thickness. In view of this dimensional ratio, the internal element 2 has an oblong section in the case of FIG. 3. As a variant, as shown in FIG. 4, two internal toric elements 2 and 2 ′ are embedded in the external element 1.

 In FIG. 5 is shown a double effect expensive seal, also composed, according to the principle of the present invention, of an external element 1 made of a first material, which cosplotely encloses an internal element 2 produced in a second matter. The external face of the external element 1 forms a median bead 11, coming into contact with a rigid surface. The two symmetrical heels 5 and 5 ′ of this external element 1 can wear anti-extrusion rings, respectively 6 and 6 ′. The internal element 2 is either toroidal, or of elliptical section as indicated in dotted lines.

 FIG. 6 shows a variant of this double-acting seal, in which the external element 1 has, on its external face, a central lip 12. This FIG. 6 also illustrates, in dotted lines, the possibility of drowning , in the external element 1, an internal element 2 of polygonal section, corresponding more or less exactly to the overall shape of the joint.

 Finally, FIGS. 7 and 8, in which the reference marks designate the parts already described above, show two other variants of double-acting seals, with internal elements 2 of trepezoidal section. In the case of FIG. 7, the large base of the trapezoidal section is situated on the side of the external face of the external element 1, while in the case of FIG. 8, it is situated on the side of the internal face of element 1. This trapezoidal shape is advantageous for maintaining the internal element 2 in the material of the external element 1 (which is forced to be molded in two stages).

 It goes without saying that the invention is not limited to the sole embodiments of this annular seal which have been described above, by way of examples; on the contrary, it embraces all of the variant embodiments and applications based on the same principle, whatever their details. This is how, in particular, one would not stray from the framework of the invention - by modifying the forms of the external element 1, according to the functions to be carried out: sealing, guiding, wiping or scraping, in any combination - by modifying the section of the internal element 2, according to the manufacturing method selected and according to the characteristics sought for the Joint; by changing the constituent materials of the external 1 and internal 2 elements, the materials indicated in the description obviously being so only by way of examples; -by completing the joint with anti-extrusion rings or added guide rings, or by removing these rings on the contrary.

Claims (5)

- CLAIMS -  1.- Annular seal, and more particularly composite seal ensuring dynamic sealing between a piston and a cylinder, or between a rod guide and a sliding piston rod in this guide, and separating two enclosures in which reigns different pressures, characterized in that an annular element (1) made of a first material, and intended to come into contact with the fluid to be sealed and with the rigid surfaces, fixed or movable, between which the joint must seal , completely encloses at least one other annular element (2), made of a second material chosen for its mechanical characteristics.  2. An annular seal according to claim 1, characterized in that the first annular element (1) is made of a material, such as polyurethane, polyamide, polyolefin or polyester elastomer, having good resistance to friction, to extrusion and chemical attack of the fluid to be sealed, while the internal element (2), embedded in the previous one, is made of a material such as natural rubber, having a very good "elastic persistence".  3. An annular seal according to claim 7 or 2, characterized in that the internal element (a), embedded in the external element (cry), is toroidal or of elliptical section.  4. An annular seal according to claim 1 or 2, characterized in that the internal element (2), embedded in the external element (1), is of polygonal section, in particular trapezoidal.  5.- Annular seal according to any one of claims 1 to 4, characterized in that it comprises two or more internal annular elements (2,2 '), embedded in the external element (1) and distributed along the length of the joint.