Patent ID: 12234927

DETAILED DESCRIPTION

FIG.1shows a rotary valve1according to the prior art. The rotary valve1comprises a housing2which defines a fluid flow path4. The fluid flow path4may be primarily used to convey high pressure gas (e.g. high pressure air), but may be used for any (high pressure) fluids. The rotary valve1comprises a valve disk6disposed in the fluid flow path4and arranged to control the pressure and the flow of fluid through the flow path4. The valve disk6is connected to a shaft8such that rotation of the shaft8causes rotation of the valve disk6within the flow path4. In a first rotational position (e.g. a ‘closed’ position), the valve disk6fully obstructs the flow path4to prevent the flow of fluid through the flow path4. In a second rotational position (e.g. an ‘open’ position), the valve disk6does not obstruct, or at least only minimally obstructs, the flow of fluid through the flow path4.

The valve housing2comprises a bore12formed therein and through which the shaft8extends. A static seal10, such as an O-ring, is located around the shaft8and within the bore12. Bushings14are provided in the bore12to aid the alignment of the shaft8.

In use, the shaft8is rotated (for example, under the control of an actuator) in order to rotate the valve disk6within the flow path4and thus vary how much the valve disk6obstructs the flow path4, in order to control the flow of the high pressure gas. However, because the shaft8is able to rotate relative to the valve housing2, the high pressure gas is able to leak between the shaft8and the housing2, to pass from the flow path4into the bore12. The seal10can prevent this to a certain extent. However, wear that arises from friction with the shaft8can weaken the seal10, particularly when the seal10is incorrectly positioned in the bore12. Sealing performance is therefore not optimal and leakage from the bore12to external to the valve1often occurs.

FIG.2shows a rotary valve100comprising a valve housing102which defines a fluid flow path104. Similarly to the rotary valve1ofFIG.1, the rotary valve100comprises a valve disk106connected to a shaft108that are arranged to control the pressure and the flow of (high pressure) fluid through the flow path4. The valve housing102comprises a bore112formed therein and through which the shaft108extends.

FIG.3shows an enlarged view of the region where the shaft108extends through the bore112. InFIG.3, a seal assembly110is positioned within the bore112and arranged to extend around the shaft108(the seal assembly110abuts against the outer circumferential surface of the shaft108). The seal assembly110comprises a first seal ring116, a second seal ring118, and an elastic ring120.

The first seal ring116comprises a first ring angled surface116a, which is a radially outward surface of the first seal ring116, radially outward from the shaft108. The second seal ring118comprises a second ring angle surface118a, which is a radially outward surface of the second seal ring118, radially outward from the shaft108. When the seal assembly110is arranged on the shaft108, the first sealing ring116is spaced apart from the second sealing ring118and the first ring angled surface116aand the second ring angled surface118aface generally towards each other in the axial direction (i.e. along the axis of the shaft108).

Preferably, the first ring angled surface116amay be oriented at an angle that is the same as an angle of second ring angled surface118a. However, the first ring angled surface116amay be oriented at an angle different to an angle of the second ring angled surface118a. For example, the first ring angled surface116amay be oriented at an angle between 30 and 60 degrees from the radially inward surface of the first seal ring116. For example, the second ring angled surface118amay be oriented at an angle between 30 and 60 degrees from the radially inward surface of the second seal ring118.

The elastic ring120is positioned in contact with the first ring angled surface116aand the second ring angled surface118a. In other words, the elastic ring120is disposed radially outwardly from and axially between the first seal ring116and the second seal ring118.

The elastic ring120, 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 ring120. As such, in the seal assembly110, the elastic ring120is arranged to load against the angled surfaces116a,118a.

The elastic ring120may comprise a first radially inner angled surface configured to contact the first ring angled surface116aand a second radially inner angled surface configured to contact the second ring angled surface118a. An angle of the first radially inner angled surface may correspond to an angle of the first ring angled surface116a. An angle of the second radially inner angled surface may correspond to an angle of the second ring angled surface118a. 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 inFIGS.2and3, the first seal ring116and second seal ring118abut against the outer circumferential surface of the shaft108, and the elastic ring120is spaced apart from the outer circumferential surface of the shaft108. The elastic ring120, as it is not in contact with the rotatable shaft108, does not load against the shaft108and thus the angled surfaces116a,118areceive the full load of the elastic ring120. Furthermore, because the elastic ring120does not load against the shaft108, it can be made of harder materials that, if it were in contact with the rotatable shaft108, would wear/damage the shaft108.

The elastic ring120may be made from a high temperature superalloy, such as an austenitic nickel-chromium-based superalloy. One example material is Iconel 718, which is part of the family of metals manufactured by the Special Metals Corporation of New York state, USA. The first and second seal rings116,118may be made from a soft material such as graphite (that will reduce wear on the shaft108). Alternatively, the first and second seal rings116,118can also be made from a high temperature superalloy (such as, for example Iconel 718). In this case, the shaft108and other parts of the valve100that are in contact with the first and second seal rings116,118may be provided with a protective metal coating.

As a result of the angle of the first ring angled surface116aand the angle of the second ring angled surface118a, the force exerted by the elastic ring120both biases the first seal ring116and the second seal ring118radially inward (e.g. to seal the seal assembly110against the shaft108) and also biases the first seal ring116and the second seal ring118apart from one another. By biasing the first seal ring116and the second seal ring118apart from one another in an axial direction, such a seal110is therefore particularly able to provide significantly improved sealing performance when it is provided around a shaft108in a bore112which has axial structures that the rings are arranged to load/brace against.

For example, as shown inFIG.3, the bore112comprises an annular shoulder122formed in the housing102. The first seal ring116is arranged to load against the annular shoulder when the first seal ring116and second seal ring118are biased apart from one another by the elastic ring120.

Additionally, located in the bore112above the seal assembly110, there is provided an annular bushing seat component124. The annular bushing seat component124is fixed to the valve housing102and is configured to support a bushing114which is provided around shaft108. The second seal ring118is arranged to load against the bushing seat component124when the first seal ring116and second seal ring118are biased apart from one another by the elastic ring120.

As such, under the loading applied by the elastic ring120, the first seal ring116effectively seals against the shaft108and the housing102, and the second seal ring118effectively seals against the shaft108and the annular bushing seat component124.

The rotary valve100may also comprise an annular static seal126(e.g. an O-ring) located between the bushing seat component124and the valve housing102. As these components are fixed relative to each other, the static seal126is able to provide excellent sealing properties.

In use, the shaft108of the rotary valve100is rotated (for example, under the control of an actuator) in order to rotate the valve disk106and change how much the valve disk106obstructs the flow path104, thus controlling the flow of the high pressure gas in the flow path104.

Considering the seal assembly110under normal pressure conditions, the force applied by the elastic ring120against the first ring angled surface116aseals the first seal ring against the shaft108and valve housing102and prevents the leakage of gas from the flow path104into the bore112.

However, in the event that the pressure of the gas exceeds the sealing pressure generated by the seal assembly110, then high pressure gas may be able to leak between the first seal ring116and the housing102. The seal assembly110may be arranged to provide a sealing pressure between the first seal ring116and the housing102that is less than a sealing pressure between the first seal ring116and the shaft108, so that in the event of a high pressure leak the gas passes between the first seal ring116and the housing102and not between the first seal ring116and the shaft108. This may be done by adjusting the angle of the first ring angled surface116a, for example.

Thus, where high pressure gas leaks between the first seal ring116and the housing102to pass from the flow path104into the bore112, the pressure in the bore112radially outward of the seal assembly110increases. This increased pressure in the region radially outward from the seal assembly110produces a force that acts on the outer circumferential surface of the seal assembly110, and particularly the outer circumferential surface of the elastic ring120.

Accordingly, the force applied by the elastic ring120to the first ring angled surface116a(and the second ring angled surface118a) is increased by the increase in pressure in the region radially outward from the seal assembly110. This increase in force allows the first seal ring116to be loaded back up against the housing102and reinstate the seal, preventing further leakage of gas from the flow path104into the bore112.

Similarly, the increase in pressure also increases the sealing force between the second sealing ring118and the bushing seat component124, preventing fluid in the region radially outward from the seal assembly110from leaking between these components.

The static seal126, when working in conjunction with the seal assembly120, is able to prevent gas from leaking between the bushing seat component124and the valve housing102from the bore112to the external environment of the valve100.

FIG.4shows a flow chart of a method500of making a rotary valve.

At step502, a housing is provided defining a fluid flow path and having a bore;

At step504a shaft is provided in the bore and connected the shaft to a valve disk disposed in the flow path.

The seal assembly100is then installed around the shaft and within the bore. This may involve step506aof installing the first seal ring around the shaft and within the bore; step506bof installing the second seal ring around the shaft and within the bore; and step506cof installing the elastic ring between the first seal ring and the second seal ring and in contact with the angled surfaces.