GB2181530A - Flashback arrestor - Google Patents

Abstract

A flashback arrestor (1) for a gas torch comprises a body (2) accommodating a flashback arrestor element (5), the body being further provided with a spring loaded self sealing valve 6. The element is porous and of material of high thermal conductivity, and has a cylindrical or tubular wall and a closed end. A gas flow pocket or recess (19) is provided between the body and the flashback element and communicates with a space (14) in the body exteriorly of the wall of the element. A gas flow path extends through the valve, through the cylindrical or tubular wall of the element to the space (14) at the exterior thereof and through said at least one pocket or recess to a space (9) adjacent the closed end of the flashback arrestor element. When an appliance is attached to the arrestor by means of a nut (3), a valve element 7 of a further valve lifts an O-ring 24 from its seat to allow gas flow through the arrestor. <IMAGE>

Description

SPECIFICATION Flashback arrestor The present invention relates to a flashback arrestor for use, for example, with gas welding and cutting appliances such as torches and blowpipes.

A known flashback arrestor comprises a nonreturn valve and a flashback arrestor element made of porous sintered metal. A gas flow path extends within the arrestorthrough an outerwall ofthe arrestor element and through holes around the periphery of a collar surrounding the arrestor element.

The present invention aims to provide an improved flashbackarrestor comprising valve.

According to the invention there is provided a flashback arrestor comprising a body through which a gas flow path extends, the body accommodating a flashback arrestor element fixed in the body and separating an upstream portion of the gas flow path from a downstream portion of the gas flow path, the body being further provided with at least one valve through which the gas flow path extends.

The flashback arrestor element is of cylindrical or tubular form, the gas flow path extending through the element from the interior thereof to a space at the exterior thereof.

The cylindrical ortubularflashback arrestor el- ement is located between an internal shoulderofthe body and a member, such as a hose end connector retained by the body, the gas flow path extending exteriorly ofthe arrestor element from said space atthe exterior ofthe arrestor element, through at least one pocket or recess provided in the shoulder, to a space within the body on the opposite side of a closed end ofthe arrestorelementtothe interiorthereof.

Theflashbackarrestorelement is a porous element of high thermal conductivity.

Gas mayflowthrough the flashback arrestor element because it is porous but a flashback is quenched by the element and thereby arrested because of the high thermal conductivity ofthe el- ement.

The flashback arrestor element is preferably of sintered metal.

The valve or valves may be open so that gas can flow along the gas flow path or closed to preventflow of gas along the gas flow path.

The flashback arrestor may comprise, as said valve or valves, a non-return valve to prevent back flow of gas through the flashback arrestor and/or a selfsealing valve which remains closed when the flashback arrestor is not connected to an appliance but is opened by the connection of the flashback arrestorto an appliance.

Preferably the flashback arrestor comprises the non-return valve. More preferably the flashback arrestor comprises both the non-return valve and the self-sealing valve, the self-sealing valve being downstream of the non-return valve.

Preferablythe flashback arrestor element ac- commodates a movable valve element of one said valve and resilient means urging the valve element to a position in which it closes the gas flow path. The resilient means may act between the closed end of the flashback arrestor element and the valve el ement. Preferably such valve is the non-return valve.

The body may accommodate resilient means, out side ofthe cylindrical flashback arrestor element and urging a movable valve element one said valve to a position in which it closes the gas flow path. Such valve may be the self-sealing valve. The resilient means may act between the closed end oftheflash back arrestor and the valve element.

According to a preferred aspect of the invention, the aforementioned resilient means acting on re spective movable valve elements of the valves also acts on opposite sides ofthe closed end oftheflash back arrestor element.

Aflashback arrestor embodying the invention is described below by way of example with reference to the accompanying drawings wherein: Figure lisa longitudinal section through the flash back arrestor; and Figure2 is a section through the outer body ofthe flashbackarrestoralong lineA-AofFigurel.

The terms "left", "right", "leftwardly" and "rightwardly" are used below with reference to the flash- back arrestor asviewed in Figure 1.

Referring to the drawings, the flashback arrestor 1 comprises an outer casing or body 2 having, at one end, a connecting nut3 and, at the other end, a hose end connector 4.

The body 2 accommodates a flashback arrestor element 5 made of sintered metal, which is porous.

The flashback arrestor 1 also comprises a nonreturn valve including a valve element 6 accommodated in the flashback arrestor element 5 and a self-sealing valve including a valve element 7. The valve element 6 of square outer section.

The outer body 2 is formed with an internal chamber consisting of coaxial bores 9, 10, 11 and 12.

Within the bores 10 and 11 is accommodated the flashback arrestor element 5. The arrestor element 5 is of cylindrical form and has one closed end and one open end. The closed end of the arrestor element 5 is seated on a shoulder 13 betweenthe bores9and 10.

A cylindrical space or gap 14 is defined between the outer cylindrical surface of the arrestor element Sand the wall ofthe bore 11.

The flashback arrestor element 5 is held fixed in position in the outer body 2 between the shoulder 13 and the hose end connector 5, a resilient sealing ring 16 being interposed between the open end ofthe arrestor element and the bose end connector4.

Within the flashback arrestor element 5 isslidably accommodated the valve element 6 and a coil spring 17,the spring urging the valve element rightwardly.

The valve element 6 comprises a projection 6a formed with an annular groove in which is located a sealing element 18.

Three pockets 19 (see Figure 2) are machined in the shoulder 13 to provide communication exteriorly of the arrestor element 5 between the cylindrical space 11 and the bore 9.

The hose end connector4 has an enlarged end portion 4a located in the bore 12 of the outer body 2, a stem 46 and a nipple4c.Abore 18extendsthrough the hose end connector 4.

Asealing ring 19 is located in an annular groove on the enlarged end portion 4a.

The enlarged end portion 4a ofthe hose end connector is retained within the bore 12 of the outer body 2 by the free edge portion 2a of the outer body being deformed or spun over the enlarged end portion 4a.

The nut 3 is formed with a radially inwardly directed annular portion 3a located in an external groove of the outer body 2to retain the nut on the outer body. An anti-friction washer 21 is also located in the groove.

At the left end ofthe outer body 2 are provided bores 28 and 29 coaxial with the bores 9, 10, 11 and 12.

The valve member7 comprises a stem 7a slidably located in bores 28 and 29 ofthe outer body 2. The valve member7 also comprises a head 7b.

An O-ring 22 is located in a recess ofthe body 2 surrounding the stem 7a.

A bore 31 extends through the valve element7 from its head 7b and opens at a port 32 in the side of the stem 7a.

On the free end ofthe valve stem 7a, within the bore 9 is mounted an O-ring housing or member 23 of hexagonal outersection.A recess ofthe member surroundsthevalve stem and accommodates an Oring 24.

A coii spring 25 acts between the closed end ofthe flashback arrestor element Sand the 0-ring housing 23 to urge the O-ring housing 23 and the valve element7 leftwardly.

When the flashback arrestor 1 is not in use, the spring 17 causes the sealing element 18to be seated on the hose end connectorto close the left end of the bore 18 ofthe hose end connector.

Also, when the flashback arrestor 1 is not in use, the spring 25 causes the O-ring to be pressed against the end surface ofthe bore 9, whereby the O-ring 24 closes the left end of the chamber within the outer body 2.

In use ofthe flashback arrestor, there is fitted onto the hose end connector 4 a gas supply hose connec- ted through a regulatorto a gas cylinder. The selfsealing valve remains closed until an appliance is attached to the flashback arrestor by means of the nut 3, the appliance then pushing the valve element 7 rightwardlyto disengage the O-ring ring 24from the left end ofthe chamber within the outer body 2.

Gas may then flow along the hose, the pressure of the gas lifting the valve element 6 and the sealing element 18 away from the hose end connector 4. The gas flows along a path through the bore of the hose end connector4, into the interior of the flashback arrestor element 5, radially outwardlythrough the cylindrical wall ofthe arrestor element into the cylindrical space 14, through the pockets 19 into the bore 9 and through the port 32 and the bore 31 of the valve element 7 to the appliance.

In the event of a flashbackfrom the appliance, the flashback is arrested at the flashback arrestor element 5thereby preventing the flashback damaging the non-return valve and travelling along the hose.

Reverse flow of gas through the flashback arrestor cannot occur because only when the pressure in the hose end connector 4 exceeds the pressure in the flashback arrestor element 5 by at least a certain amountisthesealing element18 lifted awayfromthe hose end connector.

When the appliance is unfastened from the flashback arrestor 1 the self-sealing valve is closed by the spring 25 urging the O-ring housing 23 againstthe left end of the bore 9. Hence no gas can flow from the hosethroughtheflashbackarrestor.

It will be appreciated that the flashback arrestor 1 as described above has no soldered joints orjoints made with epoxy resin (e.g. "Araldite" Registered Trade Mark). The spinning over of the outer casing 2 at 2a makes the flashback arrestortamperproof.

Claims (11)

1. Aflashback arrestorcomprising a body accommodating a flashback arrestor element, the body being further provided with at least one valve, the flashback arrestor element being a porous element of material of high thermal conductivity and having a cylindrical ortubularwall and a closed end, the flashback arrestor element being located between an internal shoulder ofthe body and a member retained by the body, at least one pocket or recess being provided at the shoulder and defined between the body and the flashback arrestor element, a space being defined in the body exterioriy ofthe wall ofthe flashback arrestor element and a space being defined in the body externally oftheflashback arrestorelementand adjacenttheclosed end thereof, a gas flow path extending through the body, the flow path extending through said at least one valve, through the cylindrical ortubularwall of the flashback arrestor element to the space atthe exterior thereof and through said at least one pocket or recess to the space adjacent the closed end oftheflashback arrestor element.

2. Aflashback arrestoraccording to claim 1, wherein the flashback arrestor element is ofsintered metal.

3. Aflashbackarrestoraccording to claim 1 or2, comprising as one said valve, a non-return valve to prevent back flow of gas through the flashback arrestor.

4. A flashback arrestor according to any preceding claim, comprising, as one said valve, a selfsealing valve which remains closed when the flashback arrestor is not connected to an appliance but is opened bytheconnection oftheflashbackarrestorto an appliance.

5. Aflashback arrestor according to claims 3 and 4, wherein the self-sealing valve is downstream of the non-return valve.

6. Aflashback arrestor according to any preceding claim, wherein the flashback arrestor element accommodates a movable valve element of one said valve and resilient means urging the valve elementto a position in which it closes the gas flow path.

7. Aflashbackarrestor according to claim 6, wherein the resilient means acts between the closed end oftheflashback arrestor element and the valve element.

8. Aflashback arrestor according to any preced ing claim, wherein the body accommodates resilient means, outside of the cylindrical flashback arrestor element and urging a movable valve element of one said valve to a position in which it closes the gas flow path.

9. Aflashbackarrestoraccording to claim 8, wherein the resilient means acts between the closed end of the flashback arrestor and the valve element.

10. Aflashbackarrestoraccording to claim 8 or 9 as appendantto claim 7, wherein the resilient means, acting on respective movable valve elements of the valves, also act on opposite sides of the closed end of the flashback arrestor element.

11. Aflashback arrestorsubstantially as descri- bed herein with reference to and as illustrated in the accompanying drawings.