Patent Description:
Rotary seals commonly comprise a pair of lip seals running on a sleeve fitted to a shaft. The lip seals require a hard bearing surface, necessitating the use of a bearing sleeve. Moreover the lip seals are typically crimped into the housing which is time consuming in assembly of the seal.

<CIT> discloses an oil or liquid-tight seal comprising first and second annular elements that each have axially and radially extending flanges and define a pocket between the axially and radially extending flanges. The seal further comprises a seal element mounted on a shaft. The seal element includes elastically deformable flanges that engage with the radially extending flanges.

<CIT> discloses a dual face rotary shaft seal assembly including a stationary casing and a sealing member. The casing houses the sealing member when it is mounted for rotation with a shaft. The sealing member carries sealing elements projecting adjacent the interior walls of the casing and a spring means which forces the sealing elements into sealing engagement with the casing under initial tension, with the result that during rotation the spring means can maintain a force on the sealing elements.

<CIT> discloses a seal cartridge assembly for providing a seal between a non-rotatable housing or casing member and a rotatable shaft. The cartridge includes a housing comprised of overlapping annular case members with each case member including an outer peripheral wall portion and an annular flange portion extending radially inwardly from the outer peripheral wall portion. The two case members are press fitted together in overlapping relationship and held together by a bonded rubber belt to provide a U-shaped cartridge housing which is press fitted and sealed to an inner bore of the non-rotatable housing. An annular sealing member is positioned within the cartridge housing and is adapted to be engageable with the shaft and rotate with the shaft within the U-shaped cartridge housing. The annular sealing member includes lip extensions extending outwardly therefrom which engage the annular flange sidewalls of the cartridge housing to provide a seal between the annular sealing member and the cartridge housing.

From a first aspect, the present disclosure provides a rotary seal comprising a first annular element, a second annular element and a seal element. The first annular element is formed from a metallic material and has a first axially extending flange and a first radially extending flange extending radially from a proximal end of the first axially extending flange.

The second annular element is formed from a metallic material and has a second axially extending flange and a second radially extending flange extending radially from a proximal end of the second axially extending flange in the same direction as the first radially extending flange. The second annular element is fixed to the first annular element, the second axially-extending flange being received radially on the first axially-extending flange and the second radially extending flange being spaced axially from the first radially extending flange to define a pocket therebetween. The seal element is located in the pocket axially between the first radially extending flange and the second radially extending flange. It makes a first sealing engagement against a first surface of the first radially extending flange and a second sealing engagement against a second surface of the second radially extending flange axially opposed to the first surface of the first radially extending flange. A reaction engagement is formed between the seal element and one of the first and second radially extending flanges, and the reaction element is generally opposite the first or second sealing engagement of the seal element with the other of the first and second radially extending flanges. The reaction engagement comprises a third raised lip formed on one of the first or the second radially extending flanges.

In an embodiment of the above, the first radially extending flange and the second radially extending flange may extend radially inwardly. In an alternative embodiment, however, they may extend radially outwardly.

In embodiments of any of the above embodiments, the second axially extending flange may be received with an interference fit with the first axially extending flange for fixing the second annular element to the first annular element. In other arrangements however, other forms of fixing may be used.

In embodiments of any of the above embodiments, the first sealing engagement may comprise a first raised lip formed on one of the seal element and the first radially extending flange.

The first raised lip may be formed on the seal element. It may be formed adjacent a surface of the seal element facing towards the first and second axially extending flanges.

In embodiments of any of the above embodiments, the second sealing engagement may comprise a second raised lip on one of the seal element and the second radially extending flange.

The second raised lip may be formed on the second radially extending flange, optionally adjacent a distal end thereof.

In embodiments of any of the above embodiments, the seal element may further comprise an annular groove extending from a surface facing towards the first and second axially extending flanges. An annular energiser may be located within the annular groove for energising the first sealing engagement.

The annular energiser may be an elastomeric O-ring.

In embodiments of any of the above embodiments, the seal element may comprise a second annular groove on a surface facing away from the first and second annular elements. An O-ring seal may be received within the second annular groove.

In embodiments of any of the above embodiments, the first axially extending flange may comprise a third annular groove on a surface facing away from the seal element. A second O-ring seal may be received within the third annular groove.

In embodiments of any of the above embodiments, the seal element may be spaced radially from the first and second axially extending flanges of the second annular element.

In embodiments of any of the above embodiments, the seal element may be made from PTFE, filled PTFE or PEEK.

The disclosure also provides a rotary assembly comprising a rotary element, a static element and a rotary seal in accordance with the disclosure mounted between the static element and the rotary element.

An embodiment of the disclosure will now be described by way of example only with reference to the accompanying drawings in which:.

With reference to <FIG>, a rotary assembly <NUM> comprises a rotary element <NUM> for example a shaft and a second element <NUM> with respect to which the rotary element <NUM> rotates. The rotary element <NUM> is supported for rotation by one or more bearings (not shown). The second element <NUM> may, in some embodiments be a static element. In other embodiments it may be a second rotary element, but one which rotates at a different speed from the rotary element <NUM>. A rotary seal <NUM> is located radially between the rotary element <NUM> and the static element <NUM> and seals a first cavity <NUM> formed on one axial side of the rotary seal <NUM> from a second cavity <NUM> formed on another side of the rotary seal <NUM>. The first cavity <NUM> and second cavity <NUM> may contain different fluids. For example in some embodiments the first cavity <NUM> may be an oil side cavity, in fluid communication with a supply of oil, and the second cavity <NUM> may be an air side cavity in fluid communication with air, for example ambient air. The rotary seal <NUM> prevents or reduces the flow of fluids from the first cavity <NUM> to the second cavity <NUM> while allowing the rotary element <NUM> to rotate.

The rotary seal <NUM> comprises three main parts, namely a first annular element <NUM>, a second annular element <NUM> and an annular seal element <NUM>. The first annular element <NUM> and the second annular element <NUM> may be formed from a metallic material such as steel. The seal element <NUM> may be formed from an elastomeric material, for example PTFE, filled PTFE or PEEK. The first annular element <NUM> may easily be formed by turning for example. The second annular element <NUM> may also easily be formed by turning for example. The seal element <NUM> may be moulded and turned if necessary.

The first annular element <NUM> is generally L-shaped in vertical cross section (as can be seen from <FIG> for example) and comprises a first axially extending flange <NUM> and a first radially extending flange <NUM> extending radially inwardly from a proximal end <NUM> of the first axially extending flange <NUM>.

The second annular element <NUM> is also generally L-shaped in vertical cross section (as can also be seen from <FIG>) and comprises a second axially extending flange <NUM> and a second radially extending flange <NUM> extending radially inwardly from a proximal end <NUM> of the second axially extending flange <NUM>.

The second annular element <NUM> is fixed to the first annular element <NUM> with the second axially-extending flange <NUM> being received radially within the first axially-extending flange <NUM>. The outer diameter OD of the second axially extending flange <NUM> may be slightly larger than the inner diameter ID of the first axially extending flange <NUM> such that the second axially-extending flange <NUM> is received with an interference fit within the first axially-extending flange <NUM>, thereby fixing the second annular element <NUM> to the first annular member <NUM>. In other embodiments, the second axially-extending flange <NUM> may be received within the first axially-extending flange <NUM> with a sliding fit, and the second annular element <NUM> be fixed to the first annular element by other means, such as a braze <NUM>, or by some other mechanical fastening. The distal end <NUM> of the second axially extending flange <NUM> may have a chamfer <NUM> to facilitate assembly of the second annular element <NUM> to the first annular element <NUM>.

The second axially extending flange <NUM> is arranged radially between the first radially extending flange <NUM> and the second radially extending flange <NUM>. The second radially extending flange <NUM> is spaced axially from the first radially extending flange <NUM> to define an annular generally U- sectioned seal-receiving pocket <NUM>. The radially outer boundary of the pocket <NUM> is formed by the first axially extending flange <NUM> and the second axially extending flange <NUM>. The respective axial boundaries of the pocket are formed by the first radially extending flange <NUM> and the second radially extending flange <NUM>.

The seal element <NUM> is received within the pocket <NUM> and sandwiched axially between the first radially extending flange <NUM> and the second radially extending flange <NUM>. A first axial side <NUM> of the seal element <NUM> makes a first sealing engagement <NUM> against a first radially extending surface <NUM> of the first radially extending flange <NUM>. A second axial side <NUM> of the seal element <NUM> makes a second sealing engagement <NUM> against a second radially extending surface <NUM> of the second radially extending flange <NUM>, axially opposed to the first radially extending surface <NUM> of the first radially extending flange <NUM>.

In this embodiment, the first sealing engagement <NUM> comprises a first axially raised lip <NUM> formed on the first axial side <NUM> of the seal element engaging with the first radially extending surface <NUM> of the first radially extending flange <NUM>, which is planar. The first lip <NUM> may be smoothly rounded or include a flattened portion for engagement with the first radially extending surface <NUM>. In other embodiments the first lip <NUM> may be formed on the first radially extending surface <NUM> instead.

The first lip <NUM> in this embodiment is formed adjacent the radially outer surface <NUM> of the seal element <NUM> towards the first and second axially extending flanges <NUM>, <NUM>. As can be seen most clearly from <FIG>, the radially outward surface <NUM> of the seal element <NUM> comprises a first annular groove <NUM> which extends radially inwardly beyond the first lip <NUM>. The first lip <NUM> is therefore in effect formed on a radially outwardly extending flange <NUM> of the seal element <NUM> defined by the annular groove <NUM>. An energising ring <NUM> is received within the first annular groove <NUM> and acts to energise the first sealing engagement <NUM>. In this embodiment, the energising ring <NUM> is a simple elastomeric O-ring, although it may take other forms such as a finger spring, garter spring or the like. Also, while the first annular groove <NUM> is shown as being generally U-shaped in cross section, in other embodiments it may have a different shape, for example a V-shaped cross section. In some embodiments, if the seal element is sufficiently resilient, the energising ring <NUM> may not be required.

The second sealing engagement <NUM> in this embodiment is comprises a second axially raised lip <NUM> formed on the second radially extending surface <NUM> of the second radially extending flange <NUM> and the second axial side <NUM> of the seal element <NUM>, which is planar. The second lip <NUM> may be smoothly rounded or include a flattened portion for engagement with the second axial side <NUM> of the seal element <NUM>. In other embodiments the second lip <NUM> may be formed on the second axial side <NUM> of the seal element <NUM> instead. In this embodiment, the second lip <NUM> is formed adjacent a distal end <NUM> of the second radially extending flange <NUM>.

In addition to the first and second sealing engagements <NUM>, <NUM> between the seal element <NUM> and the first and second annular elements <NUM>, <NUM>, there is a reaction engagement <NUM> therebetween. Such a reaction engagement <NUM> is illustrated most clearly in <FIG>. In this embodiment, the reaction engagement <NUM> is between a third axially raised lip <NUM> formed on the first radially extending surface <NUM> of the first radially extending flange <NUM> and the first axial side <NUM> of the seal element <NUM>. The reaction engagement is provided adjacent the radially inner end <NUM> of the first radially extending flange <NUM>. It is generally opposite the second sealing engagement <NUM> so that the seal element <NUM> is generally clamped axially between the third lip <NUM> and the second lip <NUM>. In effect, the third lip <NUM> limits the distance that the second annular element <NUM> may be inserted into the first annular element <NUM> during assembly. The reaction engagement <NUM> is configured such that it does not interfere with the first sealing engagement <NUM>.

It will be seen that the seal element <NUM> further comprises a second annular groove <NUM> on radially inner surface <NUM>, for example generally midway axially of the seal element <NUM> as shown. An O-ring seal <NUM> is received within the second annular groove <NUM>. As can be seen in <FIG>, the O-ring seal <NUM> makes sealing contact with the radially outer surface <NUM> of the rotary element <NUM>. The rotary element <NUM> is not provided with a bearing sleeve as in the prior art, as the seal of the present disclosure may not require one to be present.

The walls <NUM> defining the second groove <NUM> may be formed with shallow circumferentially extending grooves <NUM>. These grooves <NUM> aid conformity and assembly of the seal to the rotary or static element. In some embodiments, the O-ring seal <NUM> may not be required and the radially inner surface <NUM> of the seal element may be sufficient to make a seal with the rotary element <NUM>.

The first axially extending flange <NUM> of the first annular element <NUM> comprises a third annular groove <NUM> on its radially outer surface <NUM> facing away from the seal element <NUM>. A second O-ring seal <NUM> is received within the third annular groove <NUM>. As can be seen in <FIG>, the second O-ring seal <NUM> makes sealing contact with a radially inner surface <NUM> of the static element <NUM>, to prevent leakage of fluid from the first cavity <NUM> to the second cavity <NUM> around the radially outer edge of the seal <NUM>. In some embodiments, the second O-ring <NUM> (and third annular groove <NUM>) may be omitted and the sealing of the seal within the static element <NUM> be achieved in some other manner, for example by adhering the seal <NUM> to the static element <NUM>.

Returning to <FIG>, it can be seen that a seal cavity <NUM> is formed between the first annular element <NUM>, the second annular elements <NUM> and the seal element <NUM>. This seal cavity <NUM> is advantageous in that it will allow for the accumulation of fluid, for example oil, which may leak into the seal <NUM> from the first cavity <NUM> through the first sealing engagement <NUM> and thus potentially prevent or reduce the passage of oil into the second cavity <NUM>.

It will also be seen from <FIG>, that the radially outward surface <NUM> of the seal element <NUM> is radially spaced from the radially inner surface <NUM> of the second axially extending flange <NUM> by a spacing <NUM>. This is not essential, but it facilitates assembly of the seal <NUM> and increases the size of the seal cavity <NUM>. It also allows for some degree of radial misalignment between the seal element <NUM> and the other elements <NUM>, <NUM>.

Having described the construction of the seal <NUM>, its assembly will now be described.

As a first step the seal element <NUM> may be assembled, with the energiser <NUM> inserted into the first groove <NUM>. The O-ring seal <NUM> may be inserted into the second groove <NUM> at this stage or later.

The seal element <NUM> is then inserted into the first annular element <NUM>, and the second annular element <NUM> then mounted to the first annular element <NUM> to locate the seal element <NUM>. As discussed above, there may be an interference fit between the first and second annular elements <NUM>, <NUM>, in which case the second annular element will have to be press fitted and/or shrunk into the first annular element <NUM>. Otherwise, the second annular element <NUM> can be simply slid into the first annular element <NUM>.

The second annular element <NUM> is inserted axially into the first annular element <NUM> so as to make the first and second sealing engagements <NUM>, <NUM>. The axial movement of the second annular element <NUM> will be limited by the reaction engagement <NUM>. If the second annular element <NUM> is not interference fitted with the first annular element <NUM>, the second annular element <NUM> may be secured to the first annular element <NUM> for example by a braze <NUM>.

The O-ring seals <NUM>, <NUM> (if they are required) may then be inserted into their respective grooves <NUM>, <NUM> and the seal <NUM> the assembled to the rotary and static elements <NUM>, <NUM>.

It will be seen that the embodiments of the disclosure may exhibit a number of advantages over the traditional lip seals discussed above.

Firstly, the seal <NUM> may accommodate relatively large radial misalignments due to the seal element being free to move radially between the annular seal elements <NUM>, <NUM>.

Secondly, the nature of the materials usable for the seal element may avoid the need for a dedicated bearing sleeve to be provided on a rotary element <NUM> against which the seal <NUM> seals.

In addition, the components may be easily manufactured (for example by turning and moulding) and assembled (for example by press fitting) and fitted to equipment without the need for specialised tooling.

Also, the use of a simple O-ring energiser <NUM>, as opposed to more complex and/or metallic designs allows a reduction in cost and weight.

The construction may also reduce drag forces on the rotary element <NUM> due to the relative coefficients of thermal expansion of the seal. This is because the thermal contraction rate of the seal element <NUM> is greater than that of the metallic annular seal elements <NUM>, <NUM> in which it is received. Thus as the seal <NUM> gets colder the clearances relative to the rotary element <NUM> will increase reducing the preload drag.

Claim 1:
A rotary seal (<NUM>) comprising:
a first annular element (<NUM>) formed from a metallic material and having a first axially extending flange (<NUM>) and a first radially extending flange (<NUM>) extending radially from a proximal end (<NUM>) of the first axially extending flange (<NUM>);
a second annular element (<NUM>) formed from a metallic material and having a second axially extending flange (<NUM>) and a second radially extending flange (<NUM>) extending radially from a proximal end (<NUM>) of the second axially extending flange (<NUM>) in the same direction as the first radially extending flange (<NUM>); wherein the second annular element (<NUM>) is fixed to the first annular element (<NUM>), the second axially-extending flange (<NUM>) being received radially on the first axially-extending flange (<NUM>) and the second radially extending flange (<NUM>) being spaced axially from the first radially extending flange (<NUM>) to define a pocket (<NUM>) therebetween;
a seal element (<NUM>) located in the pocket (<NUM>) axially between the first radially extending flange (<NUM>) and the second radially extending flange (<NUM>) and making a first sealing engagement (<NUM>) against a first surface (<NUM>) of the first radially extending flange (<NUM>) and making a second sealing engagement (<NUM>) against a second surface (<NUM>) of the second radially extending flange (<NUM>) axially opposed to the first surface (<NUM>) of the first radially extending flange (<NUM>); characterised in that
a reaction engagement (<NUM>) is formed between the seal element (<NUM>) and one of the first and second radially extending flanges (<NUM>, <NUM>), and the reaction engagement (<NUM>) is generally opposite the first or second sealing engagement (<NUM>, <NUM>) of the seal element (<NUM>) with the other of the first and second radially extending flanges (<NUM>, <NUM>), and the reaction engagement (<NUM>) comprises a third raised lip (<NUM>) formed on one of the first or the second radially extending flanges (<NUM>, <NUM>).