Method and apparatus for applying rock dust to a mine wall
Rock dust is applied to a mine wall for mine fire suppression in combination with a chemical foam, by generating the foam from air and a foamable liquid in a mixing chamber, and delivering the foam through one flexible conduit and air-entrained rock dust through another flexible conduit to a portable assembly composed of a Y-joint and a delivery nozzle for combining the foam and rock dust and applying the combination directly to a mine wall.
1. A method of applying rock dust to a mine wall comprising:
entraining rock dust in air in a first flexible conduit, thereby causing a mixture of rock dust and air to flow through said first flexible conduit;
causing a flowable foam to flow through a second flexible conduit;
combining said mixture of rock dust and air taken from said first flexible conduit with said flowable foam taken from said second flexible conduit in a mixing chamber within a movable assembly, said mixing chamber having inlets connected respectively to said first and second flexible conduits, thereby producing, in said mixing chamber, a mixture of rock dust, air and foam;
causing said mixture of rock dust, air and foam to flow, from said internal chamber of the movable assembly, through a nozzle connected to said movable assembly; and
applying the mixture of air, rock dust and foam flowing through said nozzle to a mine wall by moving said movable assembly relative to the mine wall while aiming said nozzle at said mine wall;
wherein, unless said nozzle is restrained, the connection of said nozzle to the movable assembly causes said nozzle to move with said movable assembly whenever said movable assembly is moved relative to said mine wall.
2. The method according to claim 1 , in which said inlets of the mixing chamber are branches of a Y-joint.
3. The method of claim 1 , in which said flowable foam is produced by mixing a foamable liquid with air.
4. The method of claim 1 , in which said nozzle is in fixed relationship to, and movable with, said movable assembly.
5. The method of claim 1 , in which air and rock dust are mixed in a second mixing chamber and delivered from said second mixing chamber to said first conduit.
6. The method of claim 1 , in which air and rock dust are mixed in a second mixing chamber and delivered from said second mixing chamber to said first conduit, and in which the concentration of rock dust in the mixture of air and rock dust air flowing through said first conduit is adjusted by varying the aperture of a restriction through which rock dust flows into said second mixing chamber.
7. The method of claim 1 , in which air and rock dust are mixed in a second mixing chamber and delivered from said second mixing chamber to said first conduit, and in which the flow of air to be mixed with rock dust in said second mixing chamber is adjusted by varying the aperture of a restriction through which said air flows into said mixing chamber.
8. The method of claim 3 , in which the mixing of a foamable liquid with air to produce a flowable foam is carried out in a mixing block, and in which the rates at which foamable liquid and air are supplied to the mixing block are independently controlled.
9. The method of claim 3 , in which the mixing of a foamable liquid with air to produce a flowable foam is carried out in a mixing block, in which foamable liquid is fed under pressure into said mixing block, and in which the rates at which foamable liquid and air are supplied to the mixing block are independently controlled.
10. The method of claim 3 , in which the mixing of a foamable liquid with air to produce a flowable foam is carried out in a mixing block, in which the rates at which foamable liquid and air are supplied to the mixing block are independently controlled, in which foamable liquid is pumped into said mixing block by an air-driven pump driven by air supplied by a source of compressed air through a first air valve, and in which air from said source of compressed air is supplied to said mixing block through a second air valve.
11. A method of applying rock dust to a mine wall comprising:
entraining rock dust in air in a first conduit, thereby causing a mixture of rock dust and air to flow through said first conduit;
causing a flowable foam to flow through a second conduit;
combining said mixture of rock dust and air taken from said first conduit with said flowable foam taken from said second conduit, thereby producing a mixture of rock dust, air and foam;
causing said mixture of rock dust, air and foam to flow through a nozzle; and
applying the mixture of air, rock dust and foam flowing through said nozzle to a mine wall;
in which air and rock dust are mixed in a mixing chamber and delivered from said mixing chamber to said first conduit, in which the concentration of rock dust in the mixture of air and rock dust flowing through said first conduit is adjusted by controlling the flow of rock dust into said mixing chamber, in which the air to be mixed with rock dust in said mixing chamber flows into said mixing chamber through an adjustable restriction having a variable aperture, and in which the flow of rock dust into said mixing chamber is controlled in response to an air pressure drop across said adjustable restriction, said valve restricting the flow of rock dust into said mixing chamber opening to allow rock dust to flow into the mixing chamber at a greater rate as the aperture of said adjustable restriction is reduced.
12. The method of claim 11 , in which the concentration of rock dust in the mixture of air and rock dust flowing through said first conduit is adjusted by varying the aperture of an adjustable restriction through which rock dust flows into said mixing chamber.