Patent Description:
Rotary valves, such as butterfly valves, are known and include a valve disk which rotates or pivots within a flow channel to control the pressure and flow of fluid through the channel. The valve disk is rotated within the channel by a shaft connected to an actuator, which extends through the flow channel and the housing of the rotary valve. Rotary valves preferably require effective sealing around the shaft, particularly at the point where the shaft extends into the flow channel, such that fluid cannot leak out of the flow channel through the valve housing.

In the prior art (see <FIG>, for example), a static seal (e.g. an O-ring) is positioned between the rotatable shaft and the housing. However, a static seal offers poor sealing performance when exposed to the high temperatures, pressures and friction experienced by such rotary valves.

<CIT> discloses a sealing assembly comprising at least one plastic ring and an elastic ring, wherein the elastic ring is arranged in order to urge the at least one plastic ring to bear against a rotating component.

<CIT> discloses a seal assembly for sealing between two relatively movable members, the seal assembly comprising a resilient sealing ring and first and second plastic sealing rings cooperable with the resilient sealing ring to form a fluid tight seal.

<CIT> discloses a sealing assembly comprising at least one resilient ring, each resilient ring having an associated/cooperating elastomeric ring (e.g. an O-ring), and a backing ring.

<CIT> discloses a sealing arrangement comprising one elastically resilient ring, and at least one sealing ring having an inclined surface.

<CIT> discloses a sealing apparatus including an annular seal (e.g. an O-ring) and a backup ring to provide support to the annular seal.

<CIT> discloses a rotary seal configured to seal a high-pressure region from a low-pressure region and having an assembly sleeve made of a rubber elastic material and at least one pressure-activatable rotary seal element with a seal edge.

Therefore there is a need in the art for improved sealing in rotary valves.

According to a first aspect, there is provided a rotary valve as claimed in claim <NUM>.

By being arranged to act on the angled surfaces of the first seal ring and the second seal ring, the elastic ring biases the first seal ring and the second seal ring against the shaft (in the radially inward direction) to provide sealing around the shaft, and also biases the first seal ring and second seal ring apart from each other (in the axially direction) to provide sealing against parts of the housing of the rotary valve.

The elastic ring may be arranged so that pressure applied on a radially outward surface of the elastic ring increases the force biasing the first seal ring and second seal ring radially inwardly and apart from one another.

In the case where the fluid pressure experienced by the seal assembly exceeds the force(s) generated by the action of the elastic ring, fluid can leak past the first seal ring of the seal assembly and into a radial gap between the seal assembly and the valve housing. This increases the fluid pressure in the radial gap, i.e. the pressure experienced by the radially outward surface of the elastic ring and the radially outer surfaces of the first seal ring and second seal ring. Consequently, the increase in the force applied by the elastic ring to the first seal ring and second seal ring, in addition to the force applied to the radially outer surfaces of the first seal ring and second seal ring as a result of the pressure differential, leads to an enhanced increase in the sealing force of the seal assembly.

The elastic ring may comprise a first radially inner angled surface configured to contact the first ring angled surface and a second radially inner angled surface configured to contact the second ring angled surface.

An inner diameter of the first seal ring and an inner diameter of the second seal ring may each be smaller than an inner diameter of the elastic ring.

As the elastic ring is not in contact with the outer circumferential surface of the shaft, this may reduce the friction experienced by the shaft.

The first seal ring and second seal ring may each comprise graphite, and the elastic seal ring may comprise a high temperature superalloy.

Forming the seal ring of a soft material such as graphite reduces the friction and/or wear experienced by the shaft.

Each of the first seal ring, the second seal ring and the elastic seal ring may comprise a high temperature superalloy.

The high temperature superalloy may be an austenitic nickel-chromium-based superalloy.

The austenitic nickel-chromium-based superalloy may be Inconel <NUM>.

The austenitic nickel-chromium-based superalloy may comprise: between <NUM>% and <NUM>% nickel, between <NUM>% and <NUM>% chromium, and between <NUM>% and <NUM>% molybdenum.

The design of the rotary valve may reduce leakage of fluid from the flow path to external to the rotary valve compared to a design having solely a static ring-type seal located around the shaft within the bore, particularly at high pressures.

The valve may comprise an annular bushing seat component fixed to the housing and located within the bore and around the shaft; and the second seal ring may be arranged to load against the bushing seat component when the first seal ring and second seal ring are biased apart from one another.

The valve may comprise an annular static seal located between the bushing seat component and the housing.

In use, the fluid in the flow path may be a high pressure gas, for example, air.

According to a second aspect, there is provided a method of making a rotary valve according to the first aspect, the method comprising: providing the housing defining the fluid flow path and having the bore; providing the shaft in the bore and connecting the shaft to the valve disk disposed in the flow path; and installing the seal assembly around the shaft and within the bore.

The step of installing the seal assembly may comprise: installing the first seal ring around the shaft and within the bore; installing the second seal ring around the shaft and within the bore; and installing the elastic ring between the first seal ring and the second seal ring and in contact with the angled surfaces.

The method may comprise: installing an annular bushing seat component within the bore and around the shaft; and fixing the annular bushing component to the housing; wherein the bushing seat component is in contact with the second seal ring.

Certain embodiments of the present disclosure will now be described in greater detail by way of example only and with reference to the accompanying drawings in which:.

<FIG> shows a rotary valve <NUM> according to the prior art. The rotary valve <NUM> comprises a housing <NUM> which defines a fluid flow path <NUM>. The fluid flow path <NUM> may be primarily used to convey high pressure gas (e.g. high pressure air), but may be used for any (high pressure) fluids. The rotary valve <NUM> comprises a valve disk <NUM> disposed in the fluid flow path <NUM> and arranged to control the pressure and the flow of fluid through the flow path <NUM>. The valve disk <NUM> is connected to a shaft <NUM> such that rotation of the shaft <NUM> causes rotation of the valve disk <NUM> within the flow path <NUM>. In a first rotational position (e.g. a 'closed' position), the valve disk <NUM> fully obstructs the flow path <NUM> to prevent the flow of fluid through the flow path <NUM>. In a second rotational position (e.g. an 'open' position), the valve disk <NUM> does not obstruct, or at least only minimally obstructs, the flow of fluid through the flow path <NUM>.

The valve housing <NUM> comprises a bore <NUM> formed therein and through which the shaft <NUM> extends. A static seal <NUM>, such as an O-ring, is located around the shaft <NUM> and within the bore <NUM>. Bushings <NUM> are provided in the bore <NUM> to aid the alignment of the shaft <NUM>.

In use, the shaft <NUM> is rotated (for example, under the control of an actuator) in order to rotate the valve disk <NUM> within the flow path <NUM> and thus vary how much the valve disk <NUM> obstructs the flow path <NUM>, in order to control the flow of the high pressure gas. However, because the shaft <NUM> is able to rotate relative to the valve housing <NUM>, the high pressure gas is able to leak between the shaft <NUM> and the housing <NUM>, to pass from the flow path <NUM> into the bore <NUM>. The seal <NUM> can prevent this to a certain extent. However, wear that arises from friction with the shaft <NUM> can weaken the seal <NUM>, particularly when the seal <NUM> is incorrectly positioned in the bore <NUM>. Sealing performance is therefore not optimal and leakage from the bore <NUM> to external to the valve <NUM> often occurs.

<FIG> shows a rotary valve <NUM> comprising a valve housing <NUM> which defines a fluid flow path <NUM>. Similarly to the rotary valve <NUM> of <FIG>, the rotary valve <NUM> comprises a valve disk <NUM> connected to a shaft <NUM> that are arranged to control the pressure and the flow of (high pressure) fluid through the flow path <NUM>. The valve housing <NUM> comprises a bore <NUM> formed therein and through which the shaft <NUM> extends.

<FIG> shows an enlarged view of the region where the shaft <NUM> extends through the bore <NUM>. In <FIG>, a seal assembly <NUM> is positioned within the bore <NUM> and arranged to extend around the shaft <NUM> (the seal assembly <NUM> abuts against the outer circumferential surface of the shaft <NUM>). The seal assembly <NUM> comprises a first seal ring <NUM>, a second seal ring <NUM>, and an elastic ring <NUM>.

The first seal ring <NUM> comprises a first ring angled surface 116a, which is a radially outward surface of the first seal ring <NUM>, radially outward from the shaft <NUM>. The second seal ring <NUM> comprises a second ring angle surface 118a, which is a radially outward surface of the second seal ring <NUM>, radially outward from the shaft <NUM>. When the seal assembly <NUM> is arranged on the shaft <NUM>, the first sealing ring <NUM> is spaced apart from the second sealing ring <NUM> and the first ring angled surface 116a and the second ring angled surface 118a face generally towards each other in the axial direction (i.e. along the axis of the shaft <NUM>).

Preferably, the first ring angled surface 116a may be oriented at an angle that is the same as an angle of second ring angled surface 118a. However, the first ring angled surface 116a may be oriented at an angle different to an angle of the second ring angled surface 118a. For example, the first ring angled surface 116a may be oriented at an angle between <NUM> and <NUM> degrees from the radially inward surface of the first seal ring <NUM>. For example, the second ring angled surface 118a may be oriented at an angle between <NUM> and <NUM> degrees from the radially inward surface of the second seal ring <NUM>.

The elastic ring <NUM> is positioned in contact with the first ring angled surface 116a and the second ring angled surface 118a. In other words, the elastic ring <NUM> is disposed radially outwardly from and axially between the first seal ring <NUM> and the second seal ring <NUM>.

The elastic ring <NUM>, by virtue of its elastic properties, is configured to exert a radially inward force when it has been displaced (e.g. stretched) to a diameter greater than a rest diameter of the ring <NUM>. As such, in the seal assembly <NUM>, the elastic ring <NUM> is arranged to load against the angled surfaces 116a, 118a.

The elastic ring <NUM> may comprise a first radially inner angled surface configured to contact the first ring angled surface 116a and a second radially inner angled surface configured to contact the second ring angled surface 118a. An angle of the first radially inner angled surface may correspond to an angle of the first ring angled surface 116a. An angle of the second radially inner angled surface may correspond to an angle of the second ring angled surface 118a. The angle of the first radially inner angled surface may be different or the same as the angle of the second radially inner angled surface.

As can be seen in <FIG> and <FIG>, the first seal ring <NUM> and second seal ring <NUM> abut against the outer circumferential surface of the shaft <NUM>, and the elastic ring <NUM> is spaced apart from the outer circumferential surface of the shaft <NUM>. The elastic ring <NUM>, as it is not in contact with the rotatable shaft <NUM>, does not load against the shaft <NUM> and thus the angled surfaces 116a, 118a receive the full load of the elastic ring <NUM>. Furthermore, because the elastic ring <NUM> does not load against the shaft <NUM>, it can be made of harder materials that, if it were in contact with the rotatable shaft <NUM>, would wear/damage the shaft <NUM>.

The elastic ring <NUM> may be made from a high temperature superalloy, such as an austenitic nickel-chromium-based superalloy. One example material is Iconel <NUM>, which is part of the family of metals manufactured by the Special Metals Corporation of New York state, USA. The first and second seal rings <NUM>, <NUM> may be made from a soft material such as graphite (that will reduce wear on the shaft <NUM>). Alternatively, the first and second seal rings <NUM>, <NUM> can also be made from a high temperature superalloy (such as, for example Iconel <NUM>). In this case, the shaft <NUM> and other parts of the valve <NUM> that are in contact with the first and second seal rings <NUM>, <NUM> may be provided with a protective metal coating.

As a result of the angle of the first ring angled surface 116a and the angle of the second ring angled surface 118a, the force exerted by the elastic ring <NUM> both biases the first seal ring <NUM> and the second seal ring <NUM> radially inward (e.g. to seal the seal assembly <NUM> against the shaft <NUM>) and also biases the first seal ring <NUM> and the second seal ring <NUM> apart from one another. By biasing the first seal ring <NUM> and the second seal ring <NUM> apart from one another in an axial direction, such a seal <NUM> is therefore particularly able to provide significantly improved sealing performance when it is provided around a shaft <NUM> in a bore <NUM> which has axial structures that the rings are arranged to load/brace against.

For example, as shown in <FIG>, the bore <NUM> comprises an annular shoulder <NUM> formed in the housing <NUM>. The first seal ring <NUM> is arranged to load against the annular shoulder when the first seal ring <NUM> and second seal ring <NUM> are biased apart from one another by the elastic ring <NUM>.

Additionally, located in the bore <NUM> above the seal assembly <NUM>, there is provided an annular bushing seat component <NUM>. The annular bushing seat component <NUM> is fixed to the valve housing <NUM> and is configured to support a bushing <NUM> which is provided around shaft <NUM>. The second seal ring <NUM> is arranged to load against the bushing seat component <NUM> when the first seal ring <NUM> and second seal ring <NUM> are biased apart from one another by the elastic ring <NUM>.

As such, under the loading applied by the elastic ring <NUM>, the first seal ring <NUM> effectively seals against the shaft <NUM> and the housing <NUM>, and the second seal ring <NUM> effectively seals against the shaft <NUM> and the annular bushing seat component <NUM>.

The rotary valve <NUM> may also comprise an annular static seal <NUM> (e.g. an O-ring) located between the bushing seat component <NUM> and the valve housing <NUM>. As these components are fixed relative to each other, the static seal <NUM> is able to provide excellent sealing properties.

In use, the shaft <NUM> of the rotary valve <NUM> is rotated (for example, under the control of an actuator) in order to rotate the valve disk <NUM> and change how much the valve disk <NUM> obstructs the flow path <NUM>, thus controlling the flow of the high pressure gas in the flow path <NUM>.

Considering the seal assembly <NUM> under normal pressure conditions, the force applied by the elastic ring <NUM> against the first ring angled surface 116a seals the first seal ring against the shaft <NUM> and valve housing <NUM> and prevents the leakage of gas from the flow path <NUM> into the bore <NUM>.

However, in the event that the pressure of the gas exceeds the sealing pressure generated by the seal assembly <NUM>, then high pressure gas may be able to leak between the first seal ring <NUM> and the housing <NUM>. The seal assembly <NUM> may be arranged to provide a sealing pressure between the first seal ring <NUM> and the housing <NUM> that is less than a sealing pressure between the first seal ring <NUM> and the shaft <NUM>, so that in the event of a high pressure leak the gas passes between the first seal ring <NUM> and the housing <NUM> and not between the first seal ring <NUM> and the shaft <NUM>. This may be done by adjusting the angle of the first ring angled surface 116a, for example.

Thus, where high pressure gas leaks between the first seal ring <NUM> and the housing <NUM> to pass from the flow path <NUM> into the bore <NUM>, the pressure in the bore <NUM> radially outward of the seal assembly <NUM> increases. This increased pressure in the region radially outward from the seal assembly <NUM> produces a force that acts on the outer circumferential surface of the seal assembly <NUM>, and particularly the outer circumferential surface of the elastic ring <NUM>.

Accordingly, the force applied by the elastic ring <NUM> to the first ring angled surface 116a (and the second ring angled surface 118a) is increased by the increase in pressure in the region radially outward from the seal assembly <NUM>. This increase in force allows the first seal ring <NUM> to be loaded back up against the housing <NUM> and reinstate the seal, preventing further leakage of gas from the flow path <NUM> into the bore <NUM>.

Similarly, the increase in pressure also increases the sealing force between the second sealing ring <NUM> and the bushing seat component <NUM>, preventing fluid in the region radially outward from the seal assembly <NUM> from leaking between these components.

The static seal <NUM>, when working in conjunction with the seal assembly <NUM>, is able to prevent gas from leaking between the bushing seat component <NUM> and the valve housing <NUM> from the bore <NUM> to the external environment of the valve <NUM>.

<FIG> shows a flow chart of a method <NUM> of making a rotary valve.

At step <NUM>, a housing is provided defining a fluid flow path and having a bore;.

At step <NUM> a shaft is provided in the bore and connected the shaft to a valve disk disposed in the flow path.

Claim 1:
A rotary valve (<NUM>) comprising:
a housing (<NUM>) defining a fluid flow path (<NUM>);
a valve disk (<NUM>) disposed in the flow path, the disk arranged to block the flow path when the disk is in a first rotational position;
a shaft (<NUM>) extending through a bore (<NUM>) in the housing and connected to the disk such that rotation of the shaft causes rotation of the disk within the flow path; and
a seal assembly (<NUM>) arranged to extend around an outer circumferential surface of the shaft and to inhibit fluid flow from the flow path through the bore, and wherein the seal assembly comprises:
a first seal ring (<NUM>) having a first ring angled surface (116a);
a second seal ring (<NUM>) having a second ring angled surface (118a); and
an elastic ring (<NUM>) disposed between the first seal ring and the second seal ring and in contact with the angled surfaces;
wherein the elastic ring (<NUM>) is arranged to act on the angled surfaces to bias the first seal ring (<NUM>) and second seal ring (<NUM>) radially inwardly and apart from one another;
wherein an annular shoulder (<NUM>) is formed in the housing around the bore (<NUM>), and wherein the first seal ring is arranged to load against the annular shoulder when the first seal ring and second seal ring are biased apart from one another; and
wherein the seal assembly (<NUM>) is arranged to provide a sealing pressure between the first seal ring and the annular shoulder that is less than a sealing pressure between the first seal ring and the shaft so that, in use, fluid that leaks from the flow path into the bore passes between the first seal ring and the annular shoulder to increase the pressure acting on the radially outward surface of the elastic ring and the radially outer surfaces of the first seal ring and second seal ring, which in turn increases the force biasing the first seal ring and second seal ring radially inwardly and apart from one another.