FR2718212A1 - Sealing ring for a rotating shaft in a support. - Google Patents

Abstract

A sealing ring (10) for positioning between a rotating shaft and a support includes a ring body (26) made of self-lubricating material and comprising an inner surface (28) surrounding the shaft (12) and an outer peripheral channel (38); a block (40) received in a recess (18) in the support (14) and comprising a bearing surface (46); a compressible O-ring seal (48) between the channel (38) and the bearing surface (46); and connecting members (50, 52) for floatingly mounting the ring body in the block. Said sealing ring is particularly useful in heat engines and pumps.

Description

Sealing ring for a rotating shaft in a support
The invention relates to a sealing ring suitable for being interposed between a rotating shaft and a support.

Various types of sealing rings are already known which allow rotational mounting of a shaft in a support, and this under sealed conditions vis-à-vis a fluid, generally under pressure, disposed on one side of the ring.

Among the known sealing rings, the simplest are made in one piece from a flexible material, for example a synthetic elastomer. They are generally provided with a flexible lip coming into tight contact with the shaft around which they are mounted.

Such one-piece sealing rings are suitable for most common applications, but become unsuitable as soon as the peripheral speed of the shaft reaches about 10 meters / second and that the pressure of the fluid, with respect to which the sealing must be guaranteed, exceeds approximately 1 bar (105 pascals).

Furthermore, there are also known sealing rings composed of several parts assembled in the factory. Some of these rings meet difficult conditions of use, but they have the disadvantage of being expensive and available only in a few dimensions.

There are also sealing rings formed of two independent parts and intended to be mounted in closed grooves. The main drawbacks are that they are difficult to mount and that they are not kept rotating.

The object of the invention is in particular to overcome the aforementioned drawbacks.

It is in particular an object of the invention to provide a sealing ring which withstands difficult conditions of use, and this for long periods of service.

It is also an object of the invention to provide a sealing ring with a space-saving structure which can be produced to the desired dimensions.

It is also an object of the invention to provide such a sealing ring which can be produced at low cost and with current tools, bar turning or the like.

It is finally another object of the invention to provide such a sealing ring which can be easily mounted.

The invention provides for this purpose a sealing ring of the aforementioned type which comprises - a ring body formed of a self-lubricating material with low coefficient of friction and having an inner surface suitable for surrounding the rotating shaft with tight friction as well as 'an outer peripheral groove; - A frame suitable for being mounted in a housing of the support and comprising a bearing surface disposed opposite the peripheral groove of the ring body to define therewith an annular space; - A compressible O-ring housed in the annular space thus delimited between the ring body and the carcass; and - means of connection with clearance allowing floating mounting, with locking in rotation, of the ring body in the carcass.

The sealing ring of the invention is thus formed of three main parts, namely the ring body, the carcass and the O-ring, which cooperate with each other.

Each piece of the ring is adapted to its function and is made of a material chosen according to needs.

The ring body ensures a slight tightening on the shaft and it is mounted floating, with play, in the carcass, while being locked in rotation relative to the latter.

The O-ring housed in the annular space delimited between the ring body and the carcass has in particular the function of ensuring the seal between the ring body and the carcass, of ensuring a pressure on the shaft by bending of the body ring, and also to ensure perfect centering of the ring body relative to the housing of the support which receives the carcass. The seal can also absorb a slight defect in concentricity between the shaft and the housing.

The main advantages of the ring of the invention are as follows - excellent resistance to hot, cold, pressure, speed and corrosion under severe conditions of use; - possibility of being made to the desired dimensions and with simple tools, bar turning or other; - ease of mounting and design of the support; - low manufacturing cost; - possibility of being used for a wide range of applications.

In a first embodiment of the invention, the inner surface of the ring body is of smooth cylindrical shape. Sealing is then ensured only by a slight radial tightening of the ring body against the shaft. It is a dry seal without lubricant.

In a second embodiment of the invention, the inner surface of the ring body comprises at least two annular lips directed towards the shaft and forming between them at least one sealed annular chamber.

Although the ring body can then be mounted dry around the shaft, a lubricant is generally used, for example a grease based on molybdenum disulfide, graphite, etc., this lubricant being introduced for mounting in the at least one of the above-mentioned sealed annular chambers.

The self-lubricating material from which the ring body is formed is advantageously a material of the rigid or semi-rigid type. Such a material is advantageously chosen from high-performance thermoplastics, composite materials based on polytetrafluoroethylene, etc. It can incorporate fillers to reduce wear.

According to another characteristic of the invention, the carcass of the sealing ring is advantageously of generally annular shape and the housing of the support which receives it is of generally homologous cylindrical shape.

The carcass may optionally include a housing for receiving the O-ring. This receiving housing, which is machined in the carcass, is also used for positioning the ring body with the carcass.

The carcass can be force-fitted into the support housing, be glued into it or be subjected to it by any other mechanical means.

The carcass is formed from a material suitable for housing the support, or neutral for oxidation reasons.

Advantageously, the carcass is formed from the same material as the support, which makes it possible to have the same coefficient of expansion and to ensure good mechanical compatibility and in particular to avoid problems of differential expansion, of electrolytic torque. , etc.

The compressible O-ring interposed between the ring body and the carcass is advantageously chosen from an elastomer seal resistant to high temperatures and a composite seal comprising a spring steel core and a covering ensuring sealing.

The connecting means provided between the ring body and the carcass can take different forms, provided that they provide a floating mounting and prevent the rotation of the ring body relative to the carcass.

In a preferred embodiment, these connecting means comprise at least two diametrically opposite lugs formed circumferentially on the carcass and engaging with clearance respectively in at least two notches formed circumferentially on the ring body.

Preferably, a cross coupling is provided between the carcass and the ring by four lugs and four notches interlocking with play between them.

This provides a possibility of movement of the ring body relative to the carcass in two perpendicular directions which extend radially relative to the rotating shaft.

In the description which follows, given solely by way of example, reference is made to the appended drawings, in which - FIG. 1 is a half-view in partial section of a sealing ring according to the invention, interposed between a rotating shaft and support; - Figure 2 is an end view of a ring body according to the invention; - Figure 3 is a sectional view on an enlarged scale along the line III-III of Figure 2; - Figure 4 is an end view of a carcass intended to cooperate with the ring body of Figures 2 and 3; - Figure 5 is a sectional view along the line V-V of Figure 4; and - Figure 6 is a detail of Figure 5, shown on an enlarged scale.

First of all, reference is made to FIG. 1 which represents a sealing ring designated as a whole by the reference 10 and which is interposed between a rotating shaft 12 rotatably mounted around an axis XX relative to a support 14 .

The rotating shaft may, for example, be part of a heat engine and the support 14 constitute the block or the casing of this engine.

The sealing ring 10 is interposed between one end 16 of the shaft 12 and a housing 18 of the support 14. This housing 18 is delimited by an annular wall 20 of axis XX and by a flat annular bottom 22 centered on said axis .

In addition, the support 14 comprises a cylindrical wall 24 of axis XX having an internal diameter greater than the diameter of the shaft 12 thereby delimiting an annular interval subjected to the pressure P of a fluid, with respect to which the ring 10 must provide a seal.

The sealing ring 10 comprises a ring body 26 machined from a self-lubricating material with a low coefficient of friction which can be rigid or semi-rigid in nature. It may, for example, be a high-performance thermoplastic material, such as that known under the brand Arlon or else a material based on polytetrafluoroethylene such as that sold under the brand Teflon.

It may especially be a composite material based on polytetrafluoroethylene, graphite or molybdenum disulphide.

The ring body 26 is machined so as to have a cylindrical internal face 28 whose diameter is substantially less than the diameter of the shaft 12 to ensure a slight tightening on the latter. The internal face 28 is machined so as to form three annular lips 30 which delimit between them two sealed chambers 32 of annular configuration. These chambers can be empty or at least one of them can be filled with a lubricant, in particular with a grease based on molybdenum disulphide, graphite, etc.

The ring body 26 comprises an annular face 34 which is applied against the bottom 22 of the housing 18 and an opposite annular face 36 which is machined, as will be seen below.

On the side opposite the inner face 28, the ring body 26 has a peripheral annular groove 38.

The sealing ring 10 further comprises a carcass 40 of generally annular shape and comprising an external cylindrical face 42 applied against the internal cylindrical face 20 of the housing 18 and an annular face 44 applied against the annular face 22 of the housing 18.

Furthermore, the carcass 40 has an internal cylindrical bearing surface 46 which faces the groove 38. The surface 46 and the groove 38 define between them an annular gap in which is housed an O-ring seal 48. The latter is made of a compressible material, for example an elastomer resistant to high temperatures, or a composite material with a spring steel core and a covering ensuring sealing. The bearing surface 46 may be smooth or optionally include a housing 49, machined in the form of a groove, to receive the O-ring 48 and allow the positioning of the ring body with the carcass, the assembly being clipped.

As can be seen in Figures 1, 2 and 3, the ring body 26 is machined from its annular face 36 to provide four notches 50, two of them being aligned along an axis A1 and the other two along an axis A2 (Figure 2) which are perpendicular to each other and extend radially with respect to the axis XX.

In FIG. 3, it will be noted that the groove 38 has a flat bottom and not a rounded bottom as in FIG. 1.

The carcass 40 of generally annular configuration is advantageously formed from the same material as the support 14 for reasons of mechanical, thermal and electrolytic compatibility.

The carcass 40 is made in one piece with four pins 52 (Figures 1, 4 and 5) which are arranged in pairs and along two perpendicular axes B1 and B2 (Figure 4) which are suitable to correspond with the axes Al and A2 when the body of ring 26 is mounted in carcass 40.

The pins 52 are directed radially inwards and have a width slightly less than the width of the notches 50.

It will be understood that when the ring body 26 is mounted in the carcass 40 with interposition of the seal 48, the four pins 52 engage respectively in the four notches 50, which ensures a connection with play of the ring body 26 in the carcass 40. The ring body 26 can in fact struggle, with limited play, along the direction of the axes
A1 and A2, while being locked in rotation relative to the carcass.

The carcass has, as seen in section at each of the lugs 52, a shape which is similar to that of an L (Figure 6).

As shown in this figure, the inner surface 46 of the carcass 40 is connected with the annular face 44 by a chamfer 54 forming an angle α for example of 300. Similarly, the outer face 42 is connected with the annular face 44 by a chamfer 56 forming an angle, for example 15-.

The realization of the two chamfers facilitates the mounting of the carcass in the support and also the relative mounting of the carcass with the compressible seal. A slight groove formed in the carcass can be used to obtain a compact assembly by clipping with the O-ring.

Of course, other means of connection with play are possible, as long as they ensure that the ring body is prevented from rotating relative to the carcass.

It will be understood that the number of sealed chambers possibly provided by the ring body is not limited to two, as in the previous example.

The sealing ring of the invention finds multiple applications, in particular in heat engines or pumps, and makes it possible to seal the shaft with respect to a fluid which may be liquid or gaseous and possibly contain suspended particles.

The sealing ring can operate under particularly severe conditions with a peripheral speed of the shaft greater than 10 meters / second and a fluid pressure greater than 1 bar (105 pascals).

This device can operate under severe conditions with a service life of at least 10,000 hours.

Claims (10)

Claims 1.- Sealing ring suitable for being interposed between a rotating shaft (12) and a support (14), characterized in that it comprises - a ring body (26) formed of a self-lubricating material with low coefficient friction and having an inner surface (28) suitable for surrounding the rotating shaft (12) with sealed friction, as well as an outer peripheral groove (38); - A carcass (40) suitable for being mounted in a housing (18) of the support (14) and comprising a bearing surface (46) disposed opposite the peripheral groove (38) of the ring body (26) to delimit with it an annular space; - A compressible O-ring (48) housed in the annular space thus delimited between the ring body (26) and the carcass (40); and - connecting means (50,52) with clearance allowing floating mounting, with locking in rotation, of the ring body (26) in the carcass (40). 2. A sealing ring according to claim 1, characterized in that the inner surface (28) of the ring body (26) is of smooth cylindrical shape. 3.- sealing ring according to claim 1, characterized in that the inner surface (28) of the ring body (26) comprises at least two annular lips (30) directed towards the shaft (12) and forming between them at least one sealed annular chamber (32). 4. A sealing ring according to claim 3, characterized in that a lubricant is introduced for mounting in at least one of the sealed annular chambers (32). 5. A sealing ring according to one of claims 1 to 4, characterized in that the self-lubricating material from which the ring body (26) is formed is of the rigid or semi-rigid type. 6. A sealing ring according to claim 5, characterized in that the self-lubricating material is chosen from high-performance thermoplastics and materials based on polytetrafluoroethylene. 7.- sealing ring according to one of claims 1 to 6, characterized in that the carcass (40) is of generally annular shape and the housing (18) of the support (14) which receives it is of generally cylindrical shape homologous, and in that the bearing surface (46) of the carcass (40) possibly includes a housing (49) for receiving the O-ring (48). 8.- sealing ring according to one of claims 1 to 7, characterized in that the carcass (40) is formed from the same material as the support (14). 9. Sealing ring according to one of claims 1 to 8, characterized in that the compressible O-ring (48) is chosen from an elastomer seal resistant to high temperatures and a composite seal comprising a spring steel core and a covering ensuring sealing. 10.- sealing ring according to one of claims 1 to 9, characterized in that the connecting means comprise at least two lugs (52) diametrically opposite and formed circumferentially on the carcass (40) and engaging with play respectively in at least two notches (50) formed circumferentially on the ring body (26).