Patent Publication Number: US-5295734-A

Title: Method and apparatus for drilling a tunnel

Description:
FIELD OF THE INVENTION 
     The invention relates to a method by which a tunnel drilling apparatus is driven forward, and to an apparatus by which the drive is transmitted forward to the drill head, particularly in driving a tunnel in rock. 
     BACKGROUND OF THE INVENTION 
     Previously known from the applicant&#39;s earlier invention No. FI-891706 is a method of driving a drilling apparatus forward, wherein the drilling apparatus is forced from the working pit into the tunnel by means of protecting tubes, the driving power unit being in the working pit. The same method is also known from the publication GB-2 157 344. 
     U.S. Pat. No. 2,669,441 discloses how the drill head is driven forward by means of a protecting tube provided with an internal spiral system which steers excavated material towards the tunnel opening. 
     Driving the drill head forward by means of protecting tubes, which are to be installed in the tunnel, is applicable to drillings in normal and watery terrains, wherein a protection tube is often an absolute necessity because of landslippage. It is quite clear that driving the drilling apparatus forward by means of protecting tubes is also advantageous since protecting tubes must be forced into the tunnel anyway. On the other hand, a protection tube is not usually needed when drilling into rock, in which case this method is not applicable. 
     Using a rotating tube for driving an apparatus forward is also applicable for tunnel drilling, but in this case, tee protecting tube is fitted with rotating elements in the rocky wall and the other end of the protecting tube needs at least one great thrust bearing. The joints between the protection tubes, which are arranged sequentially, must be lap joints. In addition, in this case, the directional stability is not the best possible. 
     SUMMARY OF THE INVENTION 
     With the method and apparatus of this invention a crucial improvement over said disadvantages has been achieved as presented in the enclosed patent claims. 
     The main advantage of this invention is that the protecting drum ca be a tube of relatively light construction transmitting only the torsion to the drill head, no thrust bearing is needed in the drive end and the supporting rollers and bearings, needed for the rotating protecting tube, can at the same time function as transmitters of the forward drive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is more closely described as follows with reference to the enclosed drawings where: 
     FIG. 1 shows the advance of a drill head in rock; and 
     FIG. 2 shows a driving and power-transmitting head in the working pit. 
    
    
     DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a drilling apparatus advancing in rock, provided with tools (25,28) with percussion bits (26,27). The tools are supported by medium-driven cylinders (24,29) and the tools can move in their holders (22,30) parallel to their longitudinal axes. The rotating head portion (19) is supported with rollers (21) to the head drum (20). By means of an auxiliary drum (16) the head drum (20) is fitted with a collar ring (17) against which a roller (18) is leaning as a thrust bearing. For drill head steering, the head drum (20) is fitted with steering cylinders (10) attached to holders (13,14) with jointings (11,12). The counterdrum leans against the framework of the rollers (6). The roller units (5) carry rollers (6) which support the conveying tubes (1) and have wheels (7) for driving them forward. The conveying tubes (1) are provided with spiral ribbing (2) The drilling apparatus is provided with conveying tubes and rollers arranged in succession. It is advantageous to join these a units of same length one after another. The rollers can be placed in the tunnel bottom section but, in addition, the conveying tubes can also be supported by a plurality of rollers on different places in the tunnel circumference. 
     FIG. 2 shows the tunnel opening where conveying tube units and roller units are added as the tunnel advances. The rotary movement is transmitted over chains (4). A motor (33) rotates the conveying tubes by means of a gear rim (34). The motor is secured to framework (32) by means of a supporting arm (35). Roller units (5) are driven forward by a driving cylinder (31) as drilling advances and the driving power is transmitted to the drill head from the roller units (5) by means of drum section (15) and steering cylinders (10) (FIG. 1). The cylinder (31) is supported against the pit back wall with a plate (36). 
     The roller units arranged one after another, can be provided at their contact points (8) with connecting parts (FIG. 1). They can be joined together for instance so that the rollers can be drawn off the tunnel and at the same time, together with the roller units; also, the entire drilling apparatus can be pulled out in case of damage. 
     Special attention is to be paid to the fact that the invention is not restricted to the embodiments of the prior art but it can be modified within the limits of the enclosed patent claims. The rollers in the roller units can be replaced with bearing surfaces and the frame dimension of the roller units can be a multiple of the rotating tube length or divisible by its total.