AU668726B2

AU668726B2 - Improved butterfly valve

Info

Publication number: AU668726B2
Application number: AU41204/93A
Authority: AU
Inventors: Frederick Peter James Smith
Original assignee: Mm Mechanical Services & Staff
Current assignee: Fpjs Pty Ltd
Priority date: 1992-06-11
Filing date: 1993-06-11
Publication date: 1996-05-16
Anticipated expiration: 2013-06-11
Also published as: AU4120493A

Description

Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

i Name of Applicant: MM MECHANICAL SERVICES STAFF PTY LTD Actual Inventor: FREDERICK PETER JAMES SMITH Address for Service: R K MADDERN ASSOCIATES, 345 King William Street, Adelaide, South Australia, Australia Invention title: IMPROVED BUTTERFLY VALVE Details of Associated Provisional Application No(s): PL 2876 filed llth June 1992.

The following statement is a full description of this invention, including the best method of performing it known to us.

L I This invention relates to an improved butterfly valve, and in particular to a valve having an improved sealing means.

Butterfly valves are well known, and generally comprise a valve body of a generally tubular nature having a cylindrical aperture therethrough defining a valve throat or valve passage. A shaft is journalled for rotation in the valve body such that the shaft extends across the diameter of the valve throat. A circular disc or valve disc is attached to the shaft, and is arranged such that the valve disc may be rotated from a closed position where it covers the valve throat, to a fully open position where the plane of the valve disc is parallel to the central axis of the valve throat.

In known examples of butterfly valves, the valve disc may be mounted centrally on the shaft such that the plane of the disc is contiguous with the axis of the shaft.

Alternatively, the valve disc may be attached to the shaft ?0 such that the shaft is located across the surface of the valve disc. In this example, the shaft is mounted eccentrically with respect to the valve disc, and is journalled off-centre in the diameter of the valve throat such that as the shaft is rotated, the valve disc remains centrally located within the valve throat.

Such butterfly valves are normally used to control air flow, and in most cases a fluid tight seal is not required.

However, in some instances, a fluid tight seal capable of maintaining a significant pressure drop across the valve is required. In this case, known butterfly valves cannot be fabricated with sufficiently fine tolerance to ensure a tight seal. The fabrication techniques required lead to difficulty in maintaining such close tolerances. In known valves the shaft is secured to the valve disc via blocks which are in turn welded to the surface of the valve disc. It is difficult to obtain the required tolerance on the diameter of the valve disc, but further distortion will always occur when the la blocks are welded to the surface of the valve disc.

Therefore, it is an object of this invention to overcome the abovementioned fabrication difficulties, while at the same time providing an effective fluid tight seal capable of maintaining a pressure drop across the valve.

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In its broadest form, the invention, a butterfly valve, comprises a valve body having a generally cylindrical aperture therethrough defining a valve throat, a shaft journalled for rotation in the valve body such that it extends across the diameter of said valve throat, a valve disc fixed to said shaft such that the disc may be positioned across the valve throat, and an annular sealing surface comprising at least a resiliently flexible material forming a layer located around and spaced from said valve throat such that the periphery of said valve disc abuts against the sealing surface and causes resilient deflection of said sealing surface to close said valve and to assist in forming a seal around the periphery of slid valve disc.

Preferably, the inside diameter of the sealing surface in the valve throat is smaller than the outside diameter of the valve disc. The sealing surface is sufficiently flexible to allow deflection of the sealing surface as the valve disc is brought to the closed position. This ensures that the sealing surface is forced against the peripheral edge of the valve disc, thereby ensuring a fluid tight seal around the total diameter of the valve disc. Due to the movement of the sealing surface, which may occur as a result of the sealing surface being spaced from the valve throat, or by the use of a resilient means between the sealing means and valve throat, the tolerances in respect of the diameter of the valve disc and its positioning can be reasonably large. Preferably, the sealing surface tapers from either end of the valve throat to a waist or area of minimum diameter, which coincides with the periphery of the valve disc when in the closed position.

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*0i The resilient means may comprise any design which allows deflection of the sealing surface, and such designs may include an annular space between the sealing surface and the valve throat surface, or a further annular portion of resiliently flexible material such as foam, an arrangement incorporating a sprung surface, or any other type of cushioning medium.

In a further aspect of this invention, the resilient means may comprise an annular pneumatic tube having means for allowing inflation or deflation of the tube. Therefore, when the valve disc is in the closed position, the annular tube will be positioned in the throat such that it is adjacent to the periphery of the valve disc, and when the valve disc is in a closed position, the tube may be inflated thereby increasing the abutment force between the valve disc and the sealing surface. This will allow the seal to maintain a pressure drop across the valve.

Upon opening of the valve, the pneumatic tube can be deflated, thereby allowing easy opening of the valves.

A further advantage of the invention is that minimal force will be required to drive the rotation of the shaft for opening of the valve, as the resilient means allows easy movement of the valve disc from a closed position to an open or fully open position.

In order that the invention be fully understood, preferred embodiments will now be described, but it should be realised that the scope of the invention is not to be confined or restricted to the precise det 'is of the various preferred embodiments. The embodiments are illustrated in the accompanying diagrams in which:- Fig 1 shows a cross-sectional view of a butterfly valve; 3 i Fig 2 shows a part axial cross-sectional view of the valve body showing a second embodiment of the sealing surface and resilient means; Fig 3 shows a part annular cross-section of the valve body showing a third preferred embodiment of a sealing surface and resilient means; and Fig 4 shows a fourth embodiment where the resilient means comprises a pneumatic tube.

The first embodiment is shown in Fig 1, which shows a cross-sectional view of a butterfly valve 10. The valve comprises a valve body constructed from an annular cylindrical portion 11. This produces a generally cylindrical aperture which defines a valve throat 13. A shaft 14 is journalled for rotation in the valve body by bearing blocks and extends across the diameter of the valve throat 13. A valve disc 16 is fixed to the shaft 14 via attachment blocks 17. The* attachment blocks 17 mount the shaft 14 eccentrically or off-centre with respect to the valve disc 16, and the shaft 14 is journalled in the valve 10 eccentrically or offcentre so that rotation of the shaft 14 causes rotation of the valve disc 16 centrally with respect to the valve throat 13.

An annular sealing member 20 is positioned within the throat 13, and comprises a sealing surface 21 and a resilient means, which in this embodiment comprises either a space or soft material 22 between the cylindrical portion 11 of the valve body, and the sealing surface 21.

The valve disc 16 has an outer diameter which is slightly larger than the inner diameter of the annular sealing member 20. This is illustrated in Figs 2 and 3, which show depression of the sealing surface. In particular, as shown in Fig 1, the sealing surface 21 tapers from either end of the valve throat 13 to a minimum diameter or waist point which coincides with the periphery of the valve disc 16 when 4 L -i _f q_ in the closed position. Therefore, when the valve disc 16 is in the closed position where it extends across the valve throat 13, the periphery of the valve disc 16 abuts against the sealing surface 21, which deflects due to the resilient nature of the sealing surface 21, and the space or soft material 22 behind the sealing surface 21. This ensures that the sealing surface 21 will be in contact with the valve disc 16 at all points around its periphery. The tapered inner surfaces of the sealing member 20, allow the valve disc 16 to clear the outer edges of sealing surface 21 as the valve disc 16 is moving to a closed position.

Preferably, the annular sealing member 20 is formed in a resiliently flexible material, and in these embodiments, the I 5 annular sealing member 20 is fabricated from neoprene rubber Sinto a generally "cotton-reel" shape. It is then cured in an autoclave to seal the joints.

As can be seen in Fig 2, apertures must be provided in both the cylindrical portion 11 of the valve body, and the sealing surface 21 to enable the shaft 14 to pass therethrough. Therefore, the valve disc 16 is spaced from the central axis of the shaft 14 so that the periphery of the valve disc 16 abuts against the sealing surface 21 at a position spaced from these apertures.

The annular sealing member 20 has a pair of shoulders 23 i which ensure that the sealing surface 21 is spaced from the cylindrical portion 11 of the valve body. The position of the shoulders 23 may vary, such that they are closer to the central axis of the shaft 14, so as to vary the resilience of the sealing surface 21.

In a third embodiment, illustrated in Fig 3, instead of providing the shoulders 23, the flanges 12 extend past the cylindrical portion 11 of the valve body, thereby resulting in a ledge which holds the sealing surface 21 in a spaced relationship with respect to the cylindrical portion 11 of the valve body. In this embodiment, each flange 12 may be

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formed in two halves, so as to allow adjustability and ease of installation of the valve Although the embodiments shown in Figs. 2 and 3 show a space between the cylindrical portion 11 of the valve body and of the sealing surface 21, the space may be filled with a resilient material such as a sponge rubber, or other soft material, which will result in increased resilience of the sealing surface 21 and a tighter sealing force.

In an alternative, shown in Fig 4, a pneumatic tube may be positioned in the space at a point adjacent to the peripheral edge of the valve disc 16 in its closed position.

Further, the pneumatic tube 25 may be capable of being inflated or deflated, so that when the valve disc 16 is in the closed position, the tube 25 may be inflated thereby increasing the sealing force between the sealing surface 21 and the peripheral edge of the valve disc 16. Upon opening of the valve, the pneumatic tube 25 may be deflated.

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As will be seen from the above description, the invention provides the unique sealing means for a butterfly valve. In particular, the seal produced is sufficient to maintain a significant pressure drop across the valve without leakage, and i i addition the valve can be opened and closed without the requirement to exert excessive force on the shaft 14.

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Claims

1. A butterfly valve comprising a valve body having a generally cylindrical aperture therethrough defining a valve throat, a shaft journalled for rotation in the valve body such that it extends across the diametor of said valve throat, a valve disc fixed to said shaft such that the disc may be positioned across the valve throat, and an annular sealing surface comprising at least a resiliently flexible material forming a layer located around and spaced from said valve throat such that the periphery of said valve disc abuts against the sealina surface and causes resilient deflection of said sealing surface to close said valve and to assist in forming a seal around the periphery of said valve disc.

2. A butterfly valve according to claim 1 further comprising annular flanges at either end of said valve throat across which said sealing surface is positioned such that it is spaced from said valve throat.

3. A butterfly valve according to claim 1 wherein said sealing surface further comprises a pair of spaced annular shoulders, said shoulders abutting against said valve throat such that the sealing surface is spaced from said valve throat.

4. A butterfly valve according to any one of the preceding claims further comprising a resilient means positioned between said sealing surface and said valve throat.

5. A butterfly valve according to claim 4 wherein said resilient means comprises a resilient material that fills the space between said valve throat and sealing surface.

6. A butterfly valve according to claim 4 wherein said resilient means comprises a pneumatic tube that is capable of being inflated against the periphery of said valve disc so as ff t'o increase the sealing effect. 7 I *aurrrrr r Cr~

7. A butterfly valve according to any one of the preceding claims wherein said sealing surface tapers from a first diameter at either side of said valve body to a smaller second diameter within said valve throat.

8. A butterfly valve according to claim 3 wherein said sealing surface has flange portions that extend outwardly over either end of said valve throat so as to hold said sealing surface within said valve throat, said sealing surface being tapered such that said disc valve progressively engages said sealing surface as the valve closes, and further comprising resilient means positioned between said sealing surface and said valve throat.

9. A butterfly valve substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. Dated this 27th day of February 1996 MM MECHANICAL SERVICES STAFF PTY ji LTD /i By its Patent Attorneys i MADDERN 1 s^ 'Ics i 1 ABSTRACT This invention relates to a butterfly valve which provides a valve capable of maintaining a significant pressure drop across the valve when it is in a closed position. The butterfly valve comprises a valve body having a generally cylindrical aperture therethrough defining a valve throat a shaft (14) journalled for rotation in the valve body such that it extends across the diameter of the valve throat a valve disc (16) fixed to the shaft (14) such that the disc (16) may be positioned across the valve throat (13) so as to close the valve, and an annular sealing surface (21) comprising a resiliently flexible material located around the valve throat (13) such that thu periphery of the valve disc (16) abuts against the sealing surface (21) when in a closed position, the sealing surface (21) arranged with respect to the valve throat (13) so as to allow resilient deflection of the sealing surface (21) when the valve disc (16) moves into a closed position. This provides an effective seal around the periphery of the valve disc (16) which is sufficient to maintain a significant pressure drop 2C across the valve. i .1 1