GB2140886A - Flexible pipe-coupling arrangement - Google Patents

Abstract

The pipe coupling 10 shown in the Figure comprises inter-fitting male and female parts 11, 12. The part 11 has an enlarged head 17 having a curved periphery 18. The curve 18 is a circular arc of a radius equal to that of the cylinder 15. A cup sealing washer 23 seats in an underlying groove and provides a seal against leakage of gas flowing through the coupling. The part 11 can swivel through a solid angle indicated by arc R. <IMAGE>

Description

SPECIFICATION Flexible pipe couplings The invention relates to flexible pipe connections.

There is frequenty a need to install gas fire extinguishing systems in areas of buildings in which there is a known fire hazard e.g. in a computer room.

A fixed conduit system is connected back to one or more gas bottles typically containing Halon or carbon dioxide. In use, a valve is opened so that the gas flows rapidly through the conduit system to extinguish the fire.

It has proved necessary to monitor the content of the or each gas cylinder since over the course of time this can be reduced. For example, if there is a leak in the system, the gas bottle can be emptied without anyone being aware. Again if the system is repeatedly tested, no record may be kept of the number of tests or the amount of gas used at each test. It is desirable therefore to mount the gas bottle(s) on a weighing platform(s) so that the weight of the bottle plus its contents can be monitored. As the content decreases the bottle rises. In addition the gas bottles can vary in length by as much as 25mm.The final connection therefore between the inlet manifold of the extinguisher conduit system and the outlet of the gas bottle has to be flexible to accommodate the relative movement and the variable heights of different gas bottles, and is usually made through a length of flexible tube. The flexible coupling tube has to be of a reasonably large diameter, typically 2 inches or 50mm bore, and is normally a metal braided tube. Such tubes require relatively expensive end fitting and involved substantial manufacturing cost. However, not only are the coupling tubes expensive but they have an inherent stiffness due to their structure and size. This does not matter when an initial connection between a gas bottle and the manifold is made but the stiffness of the coupling will tend to stop movement of the gas bottle as its contents are exhausted.The mechanism monitoring the weight of the bottle will not therefore give a true reading. This can be highly dangerous in that it will indicate that the content of the bottle is greater than it really is.

It is therefore a prime object of the invention to provide a flexible pipe coupling specifically designed for incorporation in a gas fire extinguishing system but suitable for use wherever relative movement is likely to occur between the tubular sockets to be connected by the coupling.

Accordingly, the invention provides a flexible pipe coupling for incorporation in a gas, fire extinguishing system, said coupling comprising two interfitting tubular coupling parts, the first part having an end portion of its bore formed as a cylinder and the second part having an end portion fitting into the cylinder, characterised in that the end portion of the second part comprises an enlarged head including a first portion which is a relatively close sliding fit in the cylinder and a second portion of smaller diameter, said first portion having a curved profile in an axial plane to permit swivelling movement between the coupling parts and said second portion providing a seating for a flexible sealing ring forming a seal between the coupling parts.

The invention includes a fire extinguishing system comprising a gas bottle containing (orforcontain- ing) a fire inhibiting or retardant gas connected to a gas distributing manifold by a flexible coupling as aforesaid.

The invention will now be further described with reference to the accompanying drawings, in which: Figure 1 is a partial section through a flexible pipe coupling embodying the invention, Figure 2 is an enlarged fragmentary section of part of the coupling and Figure 3 is a diagrammatic drawing of part of a gas fire extinguishing system.

The flexible pipe coupling 10 shown in the drawings is known as the "Mitchell Coupling" and comprises male and female coupling parts 11,12 formed of stainless steel or other suitable metal. The female part 12 has a standard external tapered pipe thread 13 at one end and its bore is stepped to provide shoulder 14 and a cylinder 15 at its other end. The part 11 has an enlarged head 16 comprising a first portion 17 having a curved profile 18 and being a close sliding fit in the cylinder 15. In this example the curved profile 18 is an arc of a circle so that the portion 17 of the head corresponds to a parallel sided central slice of a sphere or ball. The circle radius is, in this example, equal to the radius of the cylinder.

The head 16 comprises an end portion 19 providing a seating 22 for a cup sectioned sealing ring 23.

The sealing ring 23 has its base against the radial wall of the portion 17 of the head and its side flanges are in contact with the wall of the cylinder 15 and the portion 19 of the head. A retaining ring 24 seats in a groove 25 and limits outward movement of the head 16.

The head 16 is similar to the piston used in a conventional air cylinder except that it has a hole through it of the same diameter as the inside diameter of the tube 11 and the edges are radiused to allow lateral movement i.e. swivelling of the tube.

As shown in the drawing the curved profile 18 enables the male part 11 to be swivelled through a solid angle diagrammatically represented by the arc R. In addition the head can be moved axially. During both pivotal or swivelling and axial relative movement between the parts the sealing ring 23 remains in contact with the cylinder wall and the head. Thus, the head portion 17 provides a mechanical bearing and the sealing ring 23 a seal.

Figure 3 shows a practical example of the coupling 10 connected between the inlet manifold 25 of a gas fire extinguishing system and a gas bottle 26. The part 12 is received in a threaded socket 26 secured to the manifold and the part 11 (Figure 1) is formed as a bent tube 27 which is connected to the normal lateral outlet socket 29 of a gas bottle. The bottle 26 is carried on a weighing platform schematically represented at 31.

The Mitchell Coupling may incorporate in one of the parts 11,12 a one way flow gas valve to prevent gas flow from the manifold back to the bottle.

Alternatively the valve may have its own housing and may be assembled into a unitary structure with the coupling. The unitary structure may also include an open/close valve.

The described Mitchell Coupling has been designed to replace the hose used heretofore to provide a flexible coupling between the inlet manifold 25 and the gas bottle 26. The Mitchell Coupling has the flexibility necessary to allow cylinders of different heights (tolerance up to 25mm) to be connected and permits limited lateral movement i.e.

swivelling. In addition when the gas source comprises an array of gas bottles, the Mitchell Coupling enables the bottles to be more closely stacked together than when a flexible hose is used. Further because of the low frictional resistance to movement between the coupling parts, the gas bottles can be continuously and accurately weighed to check that their contents are adequate without having to take into account the stiffness of a relatively inflexible connecting tube. Since the Mitchell Coupling is formed of metal it does not deteriorate with time.

Claims (10)

1. Aflexible pipe coupling comprising two interfitting tubular coupling parts, the first part having an end portion of its bore formed as a cylinder and the second part having an end portion fitting into the cylinder, characterised in that the end portion of the second part comprises an enlarged head including a first portion which is a relatively close sliding fit in the cylinder and a second portion of smaller diameter, said first portion having a curved profile in an axial plane to permit swivelling movement between the coupling parts and said second portion providing a seating for a flexible sealing ring forming a seal between the coupling parts.

2. A coupling as claimed in claim 1, further characterised in that the curved profile of the first portion is an arc of a circle whereby that portion corresponds to a parallel sided central slice of a sphere.

3. A coupling as claimed in claim 2, further characterised in that the radius of the profile circle arc is equal to the radius of the cylinder.

4. A coupling as claimed in claim 1,2 or 3, further characterised in that the sealing ring is provided by a cup seal, the web of the seal extending in a radial plane and the outer surfaces of the side flanges respectively sealing against the cylinder and the head.

5. A coupling as claimed in any one of claims 1 to 4, further characterised by a retaining ring to prevent withdrawal of the second coupling part.

6. A coupling as claimed in any one of claims 1 to 5, further characterised in that the cylinder portion of the bore of the first part is increased in diameter to form a shoulder limiting inward movement of the second coupling part.

7. A coupling as claimed in any one of claims 1 to 6, further characterised in that the outer ends of the two coupling parts are formed with thread so that they can be threadably coupled to the members to be connected thereby.

8. A coupling as claimed in any one of claims 1 to 7, further characterised by incorporating a one-way gas flow valve.

9. A coupling as claimed in any of claims 1 to 8, further characterised by incorporating an open/close gas valve.

10. Afire extinguishing system comprising a gas bottle containing (or for containing) a fire inhibiting or retardant gas connected to a gas distribution manifold by a flexible coupling as claimed in any one of claims 1 to 9.