The invention relates to a tunnel drilling apparatus provide with a working tool at drill head and to a method by means o which the drill waste is removed from the working tool insid the protecting pipe.

Previously is known tunnel drilling apparatus with one working tool a.o. from the US-patent 4,122,683. A working drill head that rotates on cutting the tunnel front wall is introduced in the publication. The excavated material is shifted into the protecting tube of the drill head and further to the rear end of the apparatus. The apparatus has a plurality of abutments immobilized against the tunnel walls enabling adjustment of the drilling direction by providing support from the tunnel walls to the protecting tube and turning the tool or the mobile part of the tool head in desired direction for instance by means of turning cylinders.

The US-patent 2,919,121 introduces an apparatus with one tunnel drilling tool by means of which excavated material is shifted into a rotating tube. Outside this tube there is another tube, the actual protecting tube enveloping the drill head. This tube is supported by wheels and expanding ring segments against the tunnel walls and adjustment of the drilling direction is provided with these wheels and ring segments.

The disadvantage of the above described solutions is characterized in that the excavated material has access to the bottom of the tunnel during working because of the placement of bit components in applied tools with respect to the protecting tube. A space is left open between the bits and the protecting tube, where excavated material simply piles up. It is complicated to force the material between the protecting tube and the driving tube and even not quite possible in

driving a tunnel in unbroken rock. In these cases, a certain quantity of drill waste always remains in the tunnel, which means hindrance to the drill head alignment, since control of driving is effected through leaning on the tunnel walls. Then disturbing drill waste piles up especially in the lower parts of the tunnel and wedges itself between the protecting tube and the tunnel.

The method and apparatus according to this invention provide' a crucial improvment of said disadvantages. In order to put this into practice, the method and apparatus are characterized in what has been described in the enclosed patent claims.

It can be considered the main advantage of the invention that the drill head can force itself through to the inner surface of the reliably waste-free tunnel which makes it possible to use a simple direct forward-driving drill head without any kind of control equipment. Furthermore, a lap joint prevents acces of loose soil from tunnel upper surface to striking bit neck portion, where it would cause interruption of drill bit stroke in no time at all. Advantageously, the method of this invention is applicable to tunnels with small-sized diameters, preferably to ones with diameters under 800 mm. In addition, the advantage of this invention is increased since it is especially difficult to furnish small-diameter drill heads with control equipment

In the following the invention is described in detail with reference to the enclosed drawing.

Figure 1 is a drill head with a tool.

Figure 2 is a drilling apparatus resting on the tunnel bottom firmly supported by the steering tunnel walls

The tool (4) in figure 1 comprises a bore bit holder (51) with openings (2), along which the drill waste is conveyed by compressed air from the bit front end to the protecting tubes (3,7). Compressed air enters the tool along a hose (8) and at least a part of it is conducted to the bit front end to convey drill waste. Between the drill bit holder and its protecting tube (3), theres is a lap joint to prevent access of drill waste to the outside of the protecting tube. Arrangement of position and direction of openings (2) makes it possible to provide an ejector affect in the lap joint so that even drill waste, which may have somehow passed the drill bit, is sucked up into the protecting tube. The collar ring (52) provided with openings is attached to the protecting tube but is, on the other hand, also in the groove of the tool, thus securing the lap joint when the bit component is moving in operation.

The protecting tube comprises two parts, one of them (7) attached to the other (6) by screws. The tool is supported with rolls (5, 17) against the protecting tubes. The hydraulic cylinder (10), the piston (11) and the piston rod (9) function as a thrust bearing. The rotating conveyor drum (15) has ribbings (14) that transmittin the rotation and conveying the waste. The line of compressed air and the hydraulic hoses (19, 20) to the drill head are arranged in the back of this ribbing. Compressed air is conducted from the rotating tube by means of a collector ring (12) to an immobile pipe. The collector ring is secured to the protecting tube with braces (18).

The tool (25) in figure 2 is provided with a drill bit (21) and a bit holder (22). Compressed air is conducted also to the bit front end and further through the bit and its openings (22) into the protecting tubes (23, 28) to convey waste as it advances. The tool head is secured with a bearing support

(24). In the protecting tubes holdfast points against tunnel bottom adjusting rings (26,36)are fitted with screws (47). Adjustming rings of different height or only sliding brackets (38) can be used on protecting tubes lower surface. The interterposition of the protecting tubes can be adjusted with turning cylinders (46) secured with brackets (45) to the protecting tubes. The rotating motion is brougth to the tool by means of a conveying drum (39) provide with an intern ribbing (40) and a compressed air line (-42) and hydraulic hoses (41) are arranged behind it. To the front edge of the conveying drum (39) a cylindrical part (37) is fastened with brackets (38) , the front face of which functions as a thrust bearing area and the shell surface as a radial bearing area. From this part the rotation is transmitted to the tool by means of a bushing (30). The inner bushing (43) is also rotating and from its inside the drill waste is shifted to the conveying drum. Around the bushing (30) an immobile hydraulic pressure distributor (33) is blocked into position by means of a collar ring (32). The roller system (34) functions as a thrust bearing and the rollers (35) as a radial bearing.

This invention is not restricted to the embodiments of prior art but it can be modified within the limits of the enclosed patent claims.