SYSTEM

FIELD OF THE INVENTION

This invention relates to a demand valve, and more particularly, but not exclusively to a demand valve for use in an oxy-fuel system.

BACKGROUND TO THE INVENTION

The applicant’s provisional patent application entitled “Oxy-fuel welding and cutting system” filed on the same date as this provisional patent application and its provisional patent application entitled “Torch for an oxy fuel welding and cutting system”, are both included herewith, in their entirety, by way of reference.

As known in the industry, oxy-fuel welding, brazing, heating and cutting are processes that use fuel gases and oxygen.

The equipment used in oxy-fuel welding, brazing, heating and cutting requires an oxygen source and a fuel gas source (usually contained in cylinders), two pressure regulators, two flexible hoses (one for each source of gas), a torch and where mandatory, a flashback arrestor. This set up may also be used for soldering and brazing.

Some regulators allow pressure of the gas from the cylinders, to be used or set in accordance EN-ISO:2503. The volume required for the task to be performed is then adjusted by the operator turning needle valves at the torch. Accurate flow control with a needle valve relies on a constant supply pressure from the regulator to the torch. The hoses are manufactured to be compatible to the gases used. A double-hose or twinned design hose is sometimes used, meaning that the oxygen and fuel hoses are joined. However, beads of molten metal given off by the cutting process can become lodged between the hoses, and burn through, releasing the pressurised gas inside, which in the case of fuel gas, usually ignites.

Fuel gas such as acetylene is not just flammable; in certain conditions it is explosive. Although it has an upper flammability limit in air of 81%, acetylene's explosive decomposition behaviour makes this irrelevant. If a detonation/deflagration wave enters the acetylene cylinder, the cylinder may be blown apart by the subsequent decomposition. Ordinary check valves / non-return valves that normally prevent backflow I reverse flow are not capable to stop a flashback as they do not contain flame quenching components.

Between the regulator and hose, and ideally between hose and torch on both oxygen and fuel lines, a flashback arrestor and/or non-return valve (check valve) may be installed to prevent flame or oxygen-fuel mixture being pushed back into either regulator at the cylinder and damaging the equipment or causing a cylinder to explode. A check valve lets gas flow in one direction only. It is usually a chamber containing a ball that is pressed against one end by a spring. Gas flow one way pushes the ball out of the way, and a lack of flow or a reverse flow allows the spring to push the ball into the inlet, blocking it.

The torch is the tool that the operator uses to perform the appropriate tasks required. It has a connection and valve for the fuel gas and a connection and valve for the oxygen, a handle for the welder to grasp, and gas mixing facilities where the fuel gas and oxygen mix, with a nozzle where the flame exits Two basic types of torches are in use; (i) nozzle mixing torches and (ii) premix - injector type torches.

Acetylene, LPG and other fuel gases are highly flammable, and form explosive mixtures with the surrounding air and/or oxygen. A major cause of accidents with gas equipment is leaking connections or poorly maintained equipment and the subsequent ignition of the leaking fuel gas which is extremely flammable can create an explosion. Even small leaks can cause a flash fire or explosion, particularly when the equipment is used in poorly ventilated areas or confined spaces such as in underground mining operations where the gases can accumulate. During the operations, sparks and spatter can be generated which are a major cause for ignition.

To detect leaks in the hoses or connections, leak detection spray is applied to all fuel gas and oxygen connections starting at the cylinder valve, regulator including all other connections up to the torch nozzle. It is especially user unfriendly when an entire length of hose needs to be sprayed and checked. Leaks will be clearly indicated by foaming bubbles at the point of leakage. A user will then know that it would be dangerous to light the gases at the nozzle and/or gas system before the leak is stopped or the leaking component is replaced.

This could be quite hazardous as a lot of this gas equipment is used underground or in confined spaces and the risk of explosions and the effect thereof can be devastating.

OBJECT OF THE INVENTION

It is an object of this invention to provide a demand valve for an oxy-fuel system which, at least partially, alleviates or assists to alleviate some of the above-mentioned hazards.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a demand valve comprising: a valve body made of a nylon material and having an operatively upper and lower parts or sections secured together with securing means, a flow path therethrough, a flow path closure device and a diaphragm to move the closure from a closed position to an open position in case of a pressure difference across the diaphragm.

The valve is used in an oxy-fuel system to supply fuel therethrough only under differential pressure conditions. The valve body and all its parts are made of nylon 6; alternatively, an O-ring and diaphragm is made of a different material.

A breather hole is located off centre in a nipple or nozzle.

A breather flow path from the breather hole to any part of the diaphragm includes at least one curvature or angled section. The breather flow path extends from outside the valve through the breather hole and terminates at an inner opening of the breather hole, operatively above the diaphragm. Alternatively, or in addition, the path is arduous and may include narrower and wider sections. An axis of the breather hole is at an angle with a plane defined by the diaphragm.

There is provided for the securing means extend through at least 10 apertures in each of the lower and upper sections, alignable to receive securing devices therethrough. The apertures are in circumferentially, outwardly extending flanges with complementary annular facing surfaces. The flanges thus have facing surfaces and extend circumferentially and outwardly from facing sides of the parts.

The diameter of the diaphragm is at least 5 cm.

The valve is configured to open at .4 bar.

The valve withstand leakage up to at least 26 bar for a period of at least 1 hour.

The flow path extends from an inlet, past a valve closure when in its open position, through diffuser holes in a conically shaped diffuser, through a regulator hole to an outlet.

The closure is biased towards its closed position when the diaphragm is balanced i.e. when there is now pressure difference over the diaphragm.

These and other features of the valve are described in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention is described below, by way of example only, with reference to the drawings in which:

Figure 1 shows a perspective view of a demand valve in accordance with the invention;

Figure 2 shows a top view of the demand valve of figure 1 ;

Figure 3 shows a cross-sectional view of the demand valve of figures 1 and

2 with the valve closed off;

Figure 4 shows the same cross-sectional view of figure 3 but with the valve open;

Figure 5 shows an exploded view of the valve of figures 1 to 4;

Figure 6 shows a top perspective view of an operatively lower part of the valve exposing some inner parts in the operatively lower part of the valve.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to the drawings, a demand valve is generally indicated by reference numeral 1 .

The demand valve 1 has a body defined by upper and lower parts (or sections), or covers (1 and 4). A flow path extends through the valve body between an inlet 2 and outlet 3. The flow path is selectively openable and closable as discussed below. An inlet nozzle 2a is screwed into a complementary screw-threaded inlet opening (bore) 2b on the side of the lower part. An outlet nozzle 3a is similarly screwed into a screw- threaded outlet opening (bore) on an opposite side of the lower part 4.

The two covers are securable together with press studs 12 and press stud securing caps 13. The press studs extend through ten holes 11 in aligned apertures in the upper and lower parts/covers. The apertures are spaced about circumferentially outwardly extending co-operating flanges of the upper and lower covers. The flanges thus have facing surfaces and extend circumferentially and outwardly from facing sides of the parts.

Parts of inner, facing surfaces of the flanges receive a circumferential diaphragm flange 15 of a diaphragm 8, therebetween. A downwardly extending annular circumferential lip 10 on the flange of the diaphragm seats in an annulus (an annular groove) 9 in the upper surface of the lower cover.

A breather nozzle 6 is situated centrally on an upper surface of the upper part. The nozzle 6 includes a breather hole 7, off-centre to the nozzle 6 and toward the side of the nozzle 6.

A conically shaped diffuser 14 locates centrally in the lower cover with its apex pointing operatively upwards. The diffuser has an upper, central aperture 14e in its apex. Diffuser holes 14d are provided and spaced around in the conical part of the diffuser. The lower, widest edge of the conical section of the diffuser terminates in a thickened cylindrical wall that sealingly secures in a complementary annular receiving formation in the lower part. The underside of the diffuser terminates in a downwardly extending tubular section 14b. This section has an outer screw thread.

A support cap 17 located underneath the diaphragm 8 is movable with the diaphragm. The cap has a central downward extending shank. The shank has a screw threaded blind bore in its lower end. The shank is slidably and snugly moveable in the upper aperture 14e of the diffuser. A valve closure 15 is short tubular with a radially extending upper flange 19. The upper flange includes an upwardly extending circumferential rim 18. The upper ridge of the rim 18 forms an O-ring seat. Apertures 16 are provided in the tubular wall of the valve closure part. The closure is biased towards its closed position when the diaphragm is balanced i.e. no flow through the valve.

An assembly pin 22 has an upper screw-threaded end 21 and a lower thickened end 22a. The pin 22 extends through a central bore 17a in the valve closure 15 and screws into the blind bore in the shank 17. The thickened end 22a has a larger diameter than the bore 17. This ensures that the pin, when under upward spring (not shown) bias and assuming that the diaphragm is in rest, forces the closure 15, and specifically the rim 18 of the closure, against an O-ring 18a to close the flow path through the valve. The bias is provided by the diaphragm or by an additional spring (not shown).

A closure and securing cap with a co-axial, raised and screw threaded annular rebate, screws into a lower complementary screw threaded bore of the lower part.

Figure 6 shows a regulator hole 20 that forms part of the flow path. The hole is elongate or oval and can be made longer or shorter along its long axis to increase or decrease flow therethrough.

With the configuration of the valve as described and shown, the valve is able to withstand 26 bar without leakage. This is specifically aided by the size of the tongue and groove or annulus that assist in securing the diaphragm and the 10 securing screw to secure the main body parts of the valve together. The valve has a relatively large diaphragm but is set to open at .4 bar when it is used in the oxy fuel welding and cutting system referred to below. It is envisaged that the valve will be made from different colours to denote different inlet and/or outlet sizes. For example, black will denote 3/8 ^th BSP left hand for the EU. White will denote 9/16 ^th UNF left hand universal fine for north and south America and blue, green or red will denote 5/8 ^th BSP left hand for, inter alia, Australia.

The valve is made of nylon 6. This has many advantages such as: there is a certain amount of memory in case of deformation of the valve body and valve parts, certainly more than is the case with prior art copper valves, it performs better and lasts longer with gasses such as acetylene and it is easier to manufacture especially considering that copper valves must have less than 70% pure copper content.

The off-centre breathing hole on the side of the breather nozzle or nipple is less likely to be contaminated, especially through manual manipulation of the valve. The diaphragm can also not be manipulated by forcing a wire or other elongate, substantially straight object through the breather hole to depress the diaphragm. The arduous path from the breather hole to the diaphragm makes it almost impossible to manipulate the diaphragm with a physical object through the breather hole. The breather hole and its axis does not point toward the diaphragm. Thus a breather flow path extends from outside the valve through the breather hole and terminates at an inner opening of the breather hole, operatively above the diaphragm.

Since the valve is made of nylon, no galvanic corrosion occurs.

In use, the valve is used in an oxy-fuel welding and cutting system. The valve is connected in the fuel gas supply line between the fuel gas supply container and a torch, specifically the upstream to a fuel gas inlet of the torch.

It will be appreciated by those skilled in the art that the invention is not limited to the precise details as described herein. For example, the diffuser need not be a separate part of the valve. Instead, it could be integrally formed into the lower valve part. Many other variations are possible without departing from the scope of the invention.