The present invention will be described with particular reference to a ventilation stopping for use in coal mines. However it will be appreciated that the device of the present invention may find applications in other than coal mines and no limitation is intended thereby.

BACKGROUND ART In underground mining operations it is necessary to provide ventilation to introduce fresh air into the mine and to remove gases. Ventilation is critical in a coal mine in order to control methane levels within the mine. Methane, which is entrained in the coal and released during working of the mine is highly explosive, particularly when combined with certain quantities of air.

Another potential hazard in coal mines is the presence of coal dust in the air which can readily ignite in the event of an explosion.

Underground mines typically have an extensive system of tunnels, only some of which are worked at one time. The costs involved in ventilating all sections of the mine are prohibitive. In order to limit costs, ventilation is normally supplied only where it is required. This is conventionally done by blocking off those sections of the mine which are not in use.

Ventilation stopping curtains made from heavy fabric materials treated with flame retardants are known. In some cases, stoppings are constructed from materials which are readily available in the mine such as fibro or the like.

Explosions are a constant hazard in underground coal mines. Typically, there is an initial, minor methane

explosion. Such an explosion is referred to as the first explosion. If the first explosion ignites the air borne coal dust, then a major or second explosion is initiated.

A disadvantage of known ventilation curtains is that in the event of an explosion they may be damaged or destroyed. When this happens, fresh air can pass from the working to the nonworking areas of the mine. Further, the flow of methane gas can no longer be controlled. These situations may present serious safety hazards to those working in the mine.

Stoppings which are strong enough to resist the force of small explosions are known. These stoppings are typically concrete block walls and are used to seal tunnels which are no longer in use. However, it is necessary to redirect ventilation through to different areas of the mine. Thus ventilation stoppings should be able to be simply and easily erected, removed and re- erected at desired locations. Consequently, those types of stoppings constructed for permanently sealing tunnels are not suitable for controlling ventilation.

It is therefore an object of the present invention to provide a device which may at least partially overcome the above disadvantages or provide the public with a useful choice.

SUMMARY OF THE INVENTION According to a first broad form of the invention there is provided a device for sealing an opening against the flow of gas, the device having a plurality of zones adapted to be at least partially filled with non-flammable material, the device being able to pivotally attach to an upper periphery of the opening and also be in sealing engagement with the opening, the device being adapted to temporarily move away from said sealing engagement in response to pressure generated by an explosion so as to at least partially release said pressure.

According to a second broad form of the present invention there is provided a method for sealing an opening, said method comprising the steps of pivotally

attaching the device as described in the first broad form to the upper periphery of the opening and at least partially filling the zones with a non-flammable material.

The device of the present invention includes a plurality of zones which are adapted to be at least partially filled with a non-flammable material. The zones may be made from any suitable material which is impervious to the flow of gas and to the non-flammable material with which the zones are to be filled. Preferably, the material is a plastics material such as vinyl, although other materials such as synthetic or natural rubber may be used.

The zones are adapted to be at least partially filled with a non-flammable material. The material may be a solid such as grout or concrete and a light weight concrete is preferred. The material may also be a particulate material. Preferably the material is a liquid and especially preferred liquid is water, which is readily available at a mine site. The zones may be filled, or at least partially filled with the material before or after installation. The zones may therefore be filled either on or off site as desired.

The zones may be in any shape which are able to hold the non-flammable material. Preferably, the zones are in the form of parallel tubes. Preferably the tubes are vertically aligned when the device is installed in an opening. The vertically aligned tubes may be open ended to facilitate on site filling. Alternatively the tubes can be sealed after filling with the non-flammable material. The device may also include a combination of sealed and open ended tubes.

In use, the device is attached to the upper periphery of the opening. The device may be attached by any suitable means and such methods are well known to persons skilled in the art. As mentioned above, the zones may be filled with non-flammable material either before or after installation. Preferably the zones are filled to capacity and preferably all zones are filled. It will be

appreciated that in some cases it may not be necessary to completely fill each zone and/or fill the zones to capacity.

The device may be formed from a single sheet of material having the zones integrally formed therein.

Alternatively the zones may be installed individually or in banks. The zones or banks thereof may be joined after installation. This enables the width of the device to be varied as required. In a particularly preferred embodiment, the zones are tubes, which may be cut to length and the bottoms sealed on site. In this way, the device may be customised to seal different sized openings.

It is often desirable to allow workers and machinery to pass through sealed openings to allow access to other parts of the mine. The device of the present invention may accordingly be provided with doors or other means of access. For example, some of the tubes may be connected by a zipper or a hook and loop type fastener such as that available under the trade mark VELCRO to allow a worker to pass through the opening.

The device is adapted to sealingly engage the opening against the flow of gas. Such engagement may be provided by any suitable means. The edges of the device may abut the perimeter of the opening. Alternatively, or in addition to, aprons or other engagement means may be provided on some parts of the perimeter and/or device to facilitate engagement. Preferably, an apron is attached to the upper part of the perimeter. As to the engagement of the device with the floor, the material filled zones of the device may abut the floor directly. Alternatively, the device may include a lower apron portion which may engage the floor. An engagement member may also be attached to the floor and the device may sealingly engage the member.

When the device is installed in an opening and the zones are filled with non-flammable material, the weight of the material typically maintains the device position. Thus the device does not move out of sealing

engagement in response to pressure variations which may normally be caused by the ventilation system.

In a particularly preferred form of the invention, the engagement means between the floor and walls of the opening is in the form of a hook and loop type fastener such as that available under the trade mark VELCRO. The VELCRO provides an acceptable gas seal between the device and the floor and walls but may readily disengage therefrom in response to pressure from an explosion.

In the event of a minor explosion in the vicinity of the opening, the pressure generated by the explosion will cause the device to move out of sealing engagement. Typically the lower part of the device will pivot away from the floor. After the explosion, the lower part of the device falls back to the floor due to the weight of the non-flammable material contained therein so as to at least partially recreate the seal. This means that in cases where there is fresh air being provided to one side of the seal, very little air will be lost through the opening to non ventilated sections of the mine. This is essential to the safety of those workers located in the ventilated part of the mine. Further, because the zones are filled with an non-flammable material they are able to at least partially absorb some of the pressure generated by the explosion.

In an especially preferred embodiment of the invention, the non-flammable material is a liquid or particulate material and the zones are adapted to disperse the material into the atmosphere in response to an explosion. When the material is water, a water barrier is created. The water barrier dampens coal dust in the air and minimises risk of further explosions caused by ignition of the coal dust. If the material is in the form of a particulate material such as a powder, the powder may entrap air borne coal dust as it falls to the floor. The material may be dispersed by any suitable means. For example the zones may contain pressure release valves

which are activated in response to pressure generated by an explosion.

In a particularly preferred embodiment, the zones are vertically aligned open ended tubes. When the device moves out of sealing engagement, the tubes pivot away from the floor and at least some of the material spills out into the atmosphere. Not all of the material will tip out of the tubes and enough will remain so that the tubes will have sufficient weight to reseal against the floor. Typically, 40 to 60t of the material will be lost.

DETAILED DESCRIPTION OF THE INVENTION By way of example only, the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic view of a preferred device of the present invention installed across an opening; Figure 2 is a detailed side view of a section of the device of Figure 1; Figure 3 is a front view of the section of Figure 2; Figure 4 is an isometric schematic view of a further preferred device of the present invention; Figure 5 is a cross section of the device of Figure 1 and Figure 6 is a cross section of a further preferred device of the present invention.

Figure 7 is a cross section of a further preferred device of the present invention.

Figure 1 illustrates a device in the form of a ventilation stopping 11 installed in a tunnel 12. The stopping has a plurality of tubes 13. The tubes 13 are attached by chains 14 to a C shaped frame 15. The frame extends along the top wall 16 of the tunnel and is attached to the tunnel by chemical anchoring points 17.

Figures 2 and 3 illustrate the attachment of the tubes 13 to the C shaped frame 15 in detail. Figure 2 also illustrates a tube 13 being filled on site with water from a hose 18. The tubes hold about 55 to about 65 litres of water when filled. The C shaped frame 15 is covered by a

vinyl apron 19. A channel 20 is attached to the floor 21 of the tunnel by chemical anchoring points 17. The channel 20 holds the bottom ends 22 of the tubes. This assists in providing an efficient seal. The stopping 11 has a vertical zipper or hook and loop type fastener 24 extending from the floor which is sized to allow a worker to pass through the stopping 11.

Figure 4 illustrates a further preferred stopping 30. The stopping is similar to that illustrated in Figure 1 and the same reference numbers are used to illustrate the same features. The stopping 30 has a door frame 31 incorporated therein.

During installation of the stopping illustrated in Figures 1 to 4, the tubes are cut to length as required. The bottom of each tube is sealed with a cap which is installed on site. The tubes are then hung from the C frame as illustrated in Figures 2 and 3. When the tubes are hung they are joined by means of a joint strip.

Figure 5 is a cross section of part of the stopping illustrated in Figure 1 to 4. The tubes 13 are joined by a cup/cord joint 33. Figure 6 illustrates an alternative method of joining the tubes 13 in which the tubes are separated by a vinyl panel 41. A zipper or hook and loop type fastener 42 is located in one of the panels.

Alternatively, the tubes may be in the form of integrally joined banks. Typical banks may include between 3 and 6 and preferably 5 tubes. The individual banks may then be joined together. The banks may be joined by any suitable means such as joint strips or a hook and loop type fastener.

Figure 7 illustrates a cross section of a preferred device of the invention and in particular illustrates a preferred means of engaging the lower portion 50 of the device 11 with the floor 51. An engagement member 52 is located on the floor and includes a pair of adjacent vinyl members 53 filled with an inert material such as stone dust or foam. The inward facing walls of the members have a layer of a hook and loop type

fastener. The lower portion of tube 13 has a double sided flap 54 complimentary to the hook and loop type fastener or members 53. The flap 54 is engaged by the members. A loose filler material 55 such as stone dust may cover the members.

It can be seen that the stopping as illustrated in the Figures is simple to install. The stopping can be customised to fit tunnels of different sizes and can be removed and re-erected as desired. Also, once installed, the stopping can provide an efficient seal to the flow of gas. In the event of a minor explosion, the tubes will be pivoted up and way from the floor. This will result in water being tipped from the tubes to provide a water barrier. This water barrier dampens any coal dust in the atmosphere and reduces the possibility of a second explosion. The remaining water in the tubes provides the tubes with sufficient weight to fall back to the floor and recreate the seal. It is estimated that a maximum of 15% of the ventilation will be lost in this manner. The stopping thereby maintains a safe level of fresh air to workers operating nearby. The stopping also reduces the risk of fire by dampening any coal dust as well as releasing pressure generated by the explosion.