1. Field of the Invention
This invention relates generally to tunnel boring machines, and more particularly to a machine that utilizes a casing centered within a casing structure, and still more particularly to one which utilizes a spoils ejector adjacent the cutting head at the forward end of the auger that is turned by the boring machine.
2. Description of the Related Art
This invention is directed to the providing of an auger boring machine of the type used in the installation of in-ground pipe. For decades, prior art boring machines have been positioned on tracks in a large hole at the initiation site of a tunnel. The machine has a power source that pushes a casing into a tunnel dug by a rotating drill head. This digging is accomplished by the power source turning an auger that extends within and is parallel to the casing. At the terminal end of the auger is a drilling head that revolves as the auger spins, the drilling head cuts soil and/or rocks loose from the ground. The cut soil and/or rock are referred to as spoils and are evacuated from the tunnel by the auger blade.
Prior art tunnel boring machines bore tunnels 4-96″ in diameter. The machines cost thousands of dollars to set up to begin the digging of a tunnel. When adjustments need to be made, it can take a day. Oftentimes, the auger used in these machines has to be removed from within the casing if a problem is encountered at the cutting head. This takes time and incurs expense.
It is thus apparent that the need exists for an improved tunnel boring machine which in addition to being easy to use, permits tunnels to be bored faster and more economically than in the past.