Rupture disk

Abstract

A rupture disk for use in a fluid control system includes a membrane and a compressible flange, around a perimeter of the membrane. The flange defines at least one perimetrically extending void.

Claims

1. A rupture disk for use in a fluid control system, the rupture disk comprising: a membrane; and a compressible flange, around a perimeter of the membrane, wherein the flange defines at least one perimetrically extending closed void and wherein the rupture disk is formed of a homogeneous material.

2. A rupture disk as claimed in claim 1, wherein the rupture disk is rotationally symmetric about an axis.

3. A rupture disk as claimed in claim 1, wherein the flange has a substantially rectangular cross-section.

4. A rupture disk as claimed in claim 1, wherein each of the one or more voids has a polygonal cross-section.

5. A rupture disk as claimed in claim 4, wherein each of the one or more voids has a diamond-shaped cross-section.

6. A rupture disk as claimed in claim 1, wherein each of the one or more voids is completely enclosed within the compressible flange.

7. A rupture disk as claimed in claim 1, wherein the rupture disk further comprises one or more solid support segments within the flange, wherein the one or more solid support segments are arranged to span one or more respective angular ranges around the flange that are not spanned by the one or more voids.

8. A rupture disk as claimed in claim 1, wherein a diameter of the rupture disk is between 5 mm and 30 mm.

9. A rupture disk as claimed in claim 1, wherein a thickness of the membrane is between 0.1 mm and 1 mm.

10. A rupture disk as claimed in claim 1, wherein a diameter of the membrane is between 5 mm and 25 mm.

11. A rupture disk as claimed in claim 1, further comprising a perimetrically-extending lip that protruded axially from an outer surface of the compressible flange.

12. A rupture disk as claimed in 11, wherein the lip extends around an entire perimeter of the rupture disk.

13. A fluid control system comprising: a rupture disk that includes: a membrane; and a compressible flange, around a perimeter of the membrane, wherein the flange defines at least one perimetrically extending closed void and wherein the rupture disk is formed of a homogeneous material; and a housing for the rupture disk.

14. A fluid control system as claimed in claim 13, wherein the housing comprises an axially-extending mating surface for mating with an outer surface of the compressible flange.

15. A fluid control system as claimed in claim 14, wherein the axially-extending mating surface is cylindrical and has a larger diameter than a diameter of the rupture disk when the flange is uncompressed.

16. A fluid control system as claimed in claim 13, comprising a compression mechanism for axially compressing the compressible flange.

17. A fluid control system as claimed in claim 16, wherein the compression mechanism comprises a washer and a rotatable nut.

18. A fluid control system as claimed in claim 13, wherein the housing defines an elongate groove arranged to mate with a lip of the rupture disk.

19. A method of installing a rupture disk within a housing, wherein the rupture disk comprises: a membrane; and a compressible flange, around a perimeter of the membrane, wherein the flange defines at least one perimetrically extending closed void wherein the rupture disk is formed of a homogeneous material, the method comprising: positioning the rupture disk within the housing.

20. A method as claimed in claim 19, comprising compressing the flange in a direction axial to the disk.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Certain examples of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 shows a plan view of a burst disk in accordance with an example of the present disclosure, in a non-deformed state;

(3) FIG. 2 shows a cross-sectional plan view of the burst disk of FIG. 1;

(4) FIG. 3 shows a cross-sectional side view of the burst disk of FIG. 1;

(5) FIG. 4 shows a cross-sectional side view of the burst disk of FIG. 1, in an uncompressed state, positioned within a high-pressure inflation valve; and

(6) FIG. 5 shows a cross-sectional side view of the burst disk of FIG. 1, in a compressed state, positioned within the high-pressure inflation valve.

DETAILED DESCRIPTION

(7) FIG. 1 shows a plan view of a burst disk 2 in an unburst state. The burst disk 2 comprises a circular membrane 4 and an annular flange 6, located around the membrane 4.

(8) FIG. 2 shows a horizontal cross-section at approximately half the depth of the burst disk 2, while FIG. 3 shows a vertical cross-section across a diameter of the burst disk 2.

(9) The burst disk 2 in this example is a single monolithic component, formed of a homogeneous material. It may be manufactured in a single 3D printing operation from aluminum, silicon, magnesium or any other suitable material.

(10) The flange 6 is arranged about the circumference of the circular membrane 4. The thickness of the membrane 4 is substantially uniform between its upper surface 4a and its lower surface 4b, and is substantially smaller than the thickness of the flange 6. For example, in the example shown in FIG. 1, the thickness of the membrane 4 is 0.3 mm, while the axial thickness of the flange 6 (including the sealing lip 8) is 2.2 mm. The membrane 4 in this example is planar when not in use, although it will be appreciated that it may distort (e.g. bulge) somewhat when subject to a pressure differential across its upper and lower faces. In other examples, the membrane 4 may curve out of the plane of the disk 2, even when not subject to a pressure gradient—e.g. it may be permanently domed.

(11) The flange defines an annular sealing lip 8. This is an axial protrusion which extends circumferentially around an upper surface of the flange 6.

(12) The flange 6 has a substantially rectangular cross-section of approximately 2.2 mm high by 1.5 mm wide, albeit with rounded corners. The flange 6 defines seven elongate cut-outs 10 that extend circumferentially within the flange 6, as shown in FIG. 2. The cut-outs 10 each have a uniform, substantially diamond-shaped radial cross-section. Each cut-out 10 has a height of 1.3 mm and a width of 1.1 mm. The provision of diamond-shaped cut-outs 10 in the flange 6 means that, upon (vertical) axial compression of the burst disk 2, the flange 6 can expand significantly in the (horizontal) radial direction.

(13) In between each cut-out is a shorter solid support section 7 of the flange 6. Thus the flange 6 has seven support sections 7. Each support section 7 is solid and homogeneous, in order to provide greater structural support to the flange 6 and to the burst disk 2. This may allow the burst disk 2 to better withstand compression forces during installation and help to protect the membrane 4 from damage. In this example, each support section 7 spans approximately 10 degrees, while each cut-out 10 defines a hollow arc of approximately 41.2 degrees. However, the provision of such support sections 7 is optional; in other examples, the flange 6 may define a single cut-out 10 as a continuous ring all around the disk 2; this may help provide rotationally-uniform expansion under of the flange 6 under axial compression.

(14) The ring-like sealing lip 8 has a uniform, substantially-triangular radial cross-section. It has a ring-like apex 8a which defines an axial extent of the disk 2. The circle defined by the apex 8a is radially aligned with the center of each cut-out 10.

(15) The diameter of the membrane is 15 mm. The total diameter of the burst disk 2 is 18 mm.

(16) FIG. 4 shows a cross-sectional side view of the burst disk 2 of FIG. 1, in an uncompressed state, positioned within a high-pressure inflation valve 11. The inflation valve 11 comprises a housing 12 that defines a central bore (oriented vertically in FIG. 4) and is substantially rotationally symmetric around the axis of the central bore. The housing 12 has a stepped inner surface comprising a horizontal radial sealing face 12a and a vertical axial sealing face 12b, where the axial sealing face 12b extends perpendicularly from the radial sealing face 12a.

(17) The axial sealing face 12b of the housing 12 defines a cylindrical region 16 within which the burst disk 2 is located. The diameter of the region 16 is fractionally greater than the diameter of the burst disk 2—e.g. being around 18.25 mm in diameter.

(18) The radial sealing face 12a provides a seat for the upper surface 6a of the flange 6 of the burst disk 2.

(19) The inflation valve 11 further comprises a metal or polymer washer 18. The washer 18 is cylindrical and comprises a central bore that is coaxial with the central bore of the housing 12. The outer circumferential (vertical) face of the washer 18 is arranged to loosely abut the axial sealing face 12b of the housing 12. The upper surface 18a of the washer 18 can be moved axially so as to apply pressure to the lower surface 6b of the flange 6 of the burst disk 2.

(20) The inflation valve 11 further comprises a rotatable nut 13, which is able to engage the lower surface 18b of the washer 18, so as to drive the washer 18 towards the burst disk 2. The nut 13 is cylindrical and comprises a central bore that is coaxial with the central bore of the washer 18 and the central bore of the housing 12. The nut 13 has a helical screw thread on its outer face that engages with a corresponding helical screw thread on the axial sealing face 12b of the housing 12.

(21) Thus, the nut 13 may be moved towards the washer 18 by rotation of the nut 13. FIG. 4 shows the nut 13 at the position where it only just abuts the lower surface of the burst disk 2 without applying significant compressive force to the flange 6.

(22) Rotation of the nut 13, in order to move the nut 13 and the washer 18 towards the disk 2, causes the washer 18 to push against the underside 6b of the flange 6 of the burst disk 2. The axial movement of the washer 18 causes the burst disk 2 to be compressed between the upper face 18a of the washer 18 and the radial sealing face 12a of the housing 12. The provision of the washer 18 means that the burst disk 2 is not directly subject to the rotational forces caused by the rotation of the nut 13, which might otherwise damage the flange 6 or membrane 4.

(23) FIG. 5 shows a cross-sectional side view of the burst disk 2 of FIG. 4 in which the nut 13 has been rotated in order to compress the burst disk 2 against the radial sealing face 12a of the housing 12.

(24) This compression forms an axial seal between the burst disk 2 and the housing 12 as a result of radial expansion of the flange 6 of the burst disk 2, which is caused by the axial deformation and radial expansion of the flange around the cut-outs 10, under compression. This radial expansion establishes a tight interface between the vertical outer surface 6c of the flange 6 and the axial sealing face 12b of the housing 12. This prevents the axial passage of fluid around the outside of the burst disk 2.

(25) Additionally, a concave circular groove 12c extends circumferentially around the radial sealing face 12a of the housing 12. The groove 12c is dimensioned to mate with the sealing lip 8 of the burst disk 2 to form a seal for preventing the passage of fluid radially past the radial sealing face 12a. This radial seal is formed as a result of the interface between the sealing lip 8 and the groove 12c, as the washer 18 presses the lip 8 into the groove 12c.

(26) The inner surface of the nut 13, the inner surface of the washer 18 and the lower surface of the burst disk 2 together bound a first volume 14. The housing 12 and the upper surface of the burst disk 2 together bound a second volume 20. In use, the first volume 14 is fluidly connected to a high pressure chamber, e.g. a cylinder of compressed gas, and the second volume 20 is connected to a lower pressure chamber, e.g. an inflatable safety device in a deflated state at atmospheric pressure.

(27) The provision of two seals—one radial and one axial—between the first volume 14 and the second volume 20 helps to ensure that fluid does not leak from the high pressure chamber to the low pressure chamber, even if the performance one of the seals is impaired for any reason.

(28) The burst disk 2 is designed such that, when the inflation valve 11 is activated to pass fluid through the main axial bore, the membrane 4 will rupture, thus allowing pressure to vent from the high pressure chamber to the low pressure chamber. The burst disk 2 of FIGS. 1-5 is designed to rupture at a pressure differential of 225 bar, although it will be appreciate that burst disks may be engineered for many different burst pressures, depending on the application.

(29) In some examples, an engagement rod (not shown) may be arranged to apply axial pressure over at least part of the upper surface 4a of the membrane 4, thus reducing the pressure differential across the burst disk 2. In such an example, the thickness of the membrane 4 may be selected such that the removal of the engagement rod causes the pressure differential to increase above a predetermined threshold, thus causing the burst disk 2 to rupture.

(30) In alternative examples, the burst disk 2 may instead be a puncture disk. Thus the membrane 4 may be designed to be punctured by a puncturing element, such as a needle (not shown).

(31) The engagement rod (or puncturing element) may be actuated in an emergency (e.g. by an electronic control system, or by a human user) in order to rupture the disk 2 and release high-pressure fluid from the high pressure chamber, through the inflation valve 11. For example, the valve 11 may be used in the inflation mechanism of an evacuation raft on an airplane.

(32) The burst disk 2 (or puncture disk) may be installed between the housing 12 and the nut 13 without the need for lubricant, or with only a small quantity of lubricant, as the burst disk 2 does not establish an interference fit with the housing 12 until it is compressed by the relative movement of the nut 13 towards the housing 12.

(33) As the burst disk 2 is a single monolithic structure, it may be manufactured conveniently and cheaply using an additive manufacturing process such as 3D printing. The use of 3D printing may also allow the cut-outs 10 within the flange 6 of the burst disk 2 to be fabricated with small dimensions.

(34) Although the present disclosure has been described with reference to one particular orientation, it will be appreciated by those skilled in the art that the present disclosure may be implemented in any orientation, and references to “upper”, “lower”, “vertically”, etc. herein should be interpreted accordingly.

(35) In another set of examples, the burst disk 2 may be retained in a housing, similar to the housing 12 of FIG. 4, which is provided for the purposes of an over-pressure safety device, rather than as an inflation valve. For example, the housing may be located in the wall of a gas cylinder, with the burst disk 2 designed to ruptured spontaneously if the pressure in the cylinder exceeds a threshold level (relative to the ambient pressure outside the cylinder), to prevent the cylinder from exploding dangerously.

(36) It will be appreciated by those skilled in the art that the disclosure has been illustrated by describing several specific examples thereof, but is not limited to these examples; many variations and modifications are possible, within the scope of the accompanying claims.