The invention relates to a method for control of the advance of tunnel drilling apparatus in soil or rock, by means of which the forward drive is effected by a power unit through pushing the rear end of the drilling apparatus at the tunnel opening, all through the tunnel. As the tunnel drive advances, the drilling apparatus can be furnished with extensions, from the rear end of which the pushing is effected.

Previously is known a control system for forward driven drilling apparatus, wherein the control of the driving force is dependent on the torque of the drilling apparatus. The tool in the drill head cuts the tunnel front wall through rotation. The rotary motion is transmitted to the drill head from the tunnel opening in general by the rotating soil-conveying tubes. The torque of the conveying tube system is monitored and as the torque drops, the drilling apparatus is driven forward.

An applicable method is also to provide the tool in the drill head with a relatively short feed of its own, the length of which the tool moves on, drilling the tunnel, and when the feed travel comes to its end, the tool reverts to start and the entire drilling apparatus is driven forward respectively. This procedure is known e.g. from the GB-publication No. 2 091 316 and the US-patent No. 4,167,289.

The disadvantage of a torque montitoring control method is the growth of torque when the tunnel drive advances. The farther the tunnel work advances the more the resistance of rotation drops, which can be caused for instance by the conveying tubes transmitting the torque. Therefore, when the tunnel drive advances, the control system becoitfes insensible to tool hindrances far from the tunnel opening and damage pf tool is quite possible.

In a system where the tool is provided with an individual built-in feed motion in the drill head, the mounting of tool becomes complicated and even the control syst-em must be of a kind that senses the qualities and variations of soil ahead.

With the method and apparatus provided by this invention, a crucial improvement of said disadvantages has been achieved. To put this into practice, the method of this invention is characterized in what has been presented in patent claim 1 ^* , and the apparatus in what has been presented in patent claim 8.

It can be considered the main advantage of this invention that feed-back is received uninteruptedly about the relatively great driving force towards the driving power unit rear end and its effect on the drill head. Thereby the driving force is not allowed to rise so much that it could damage the .tool. When the drilling apparatus advances in the tunnel, the tool at the drill head is always the first one to hit the tunnel front wall and the impact causes raise of pressure in the tool supporters and this information is exploited in the invention. With the apparatus according to the invention, the drill head, the conveying tubes as well as the protecting tubes (if used) are fed all the way, uninterrupted, through the tunnel. As per the above mentioned publication, interruption is caused a.o. by the step-by-step push of the protecting tubes in order to follow the drill head, since there is no forward drive of the protecting tubes during drilling.

In the following the invention is more closely described with reference to the enclosed drawing in which Fig. 1 is a drill head provided with two tools. Fig. 2 is a driving power unit in the working pit. Fig. 3 is a drill head with one tool.

Fig. 4 is a drilling apparatus, where the tool affecting force turns to pressure information in the working pit. Fig. 5 is a drilling apparatus, where the tool affecting force turnes to pressure information in the working pit .

Figure 1 shows a drilling apparatus for tunnel drive in rock, provided with percussion tools (25 and 28). These tools are supported against the medium-driven cylinders (24 and 29) and movable in their holders (23 and 30) parallel with their longitudinal axis. Thereby the forces affecting the tool bits (26, 27) parallel with the longitudinal axis, are detectable as pressure in the support cylinders (24, 29). The rotating drill head (19) is supported with rolls (21) against the front end drum (29). By means of an auxiliary drum (16) a collar ring (17) is fixed to the front end cylinder, which is also the support face for the roll (18) that functions as thrust bearing. In connection with this as thrust bearing functioning roll or with the collar ring, also a medium-driven pressure sensor can be installed. Rise of pressure due to forces towards the drill bits, can be detected from this sensor and transmitted to the tunnel working pit as pressure information along hose (9) resting on rollers (5,6,7) at the bottom of the tunnel.

The hoses which transmit pressure information can also be arranged behind the spiral ribbing (2) in the conveyor drum (1). The chains (4) transmit the torsion from one conveyor drum to another.

For the control of the drill head, the head is provided with steering cylinders (10) fastened through joints (11, 12) to the holders (13) and (14). The counterdrum (15) leans on the

roller frames (5). The steering cylinders (10) are medium- driven and the pressures towards the cylinder can also be de-tected as rise of pressure in these cylinders. The pressure hoses of these cylinders are, preferably, taken to the tunnel working pit along the roller frames.

Figure 2 shows the power unit (31) in the working pit. A cylinder is provided as power unit resting on the frame (32)'. The cylinder is supported against the pit back wall with a plate (36). The motor (33) rotates the conveying tube by means of a cog-wheeled annular part (34) in the rear end of the conveyor tube. The entire drilling unit is driven by the cylinder as drilling proceeds, e.g. controlled by pressure information received from one of the actuators in figure 1.

Figure 3 shows a cylinder (46), which functions as thrust bearing behind the tool (40) in the drilling head. The tool is enveloped in the protecting tubes (39,43) and provided with a drill bit (37) with openings (38). The tool rests on rollers (41) and the thrust bearing on rollers (52, 53). The compressed-air hose (44) and the hydraulic hoses (55, 56) are taken to the drill head behind the ribbing (50) of the rotating conveyor tube (51). Around cylinder (46) there is an immobile ring (48) provided with an inside groove along which compressed air can uninteruptedly enter the drill head through pipe (44). Hydraulic pressure is conducted to both sides of piston (47) through holes bored in cylinder (46). The forces towards the tool can be detected as rise of pressure in the hydraulic cylinder which functions as thrust bearing in the working pit.

Figure 4 shows an auxiliary frame (73) placed on framework (74) and driven by the actual driving cylinder (72) at the rear end (71) of the auxiliary frame. Inside the auxiliary

frame there is an immobile collar ring (68) from which small- sized cylinders (67) push the thrust bearing gart (65, 66), which can slide within the auxiliary frame, and a part (64, 61,62) conducting compressed-air. The motor rotates by means of an articulated shaft (69) the center part (61) which is mounted with bearings to rotate within the collar part (64). Inside the protecting tube (57), which is forced into the tunnel, a screw (75) rotates conveying soil or rock off the tunnel. Simultaneously, the centre tube (59) of the screw works as a conducting pipe of compressed air. The tool in the drill head is rotating and joined directly to the centre tube of the conveying tube. Thereby the forces toward tool are transmitted along tube (59) to the thrust bearing (66) and further over it to the cylinders (67). The flange (60) of the auxiliary frame (73) transmits the driving force (72) of the driving cylinder (72) to the protecting tube (57) but the driving force against the tool must at the same time come through the cylinders (67), whereat it is possible to get information about their pressure from the force toward the tool .

Figure 5 shows a fragment of drilling apparatus in the working pit, where the hydraulic cylinder functions as thrust bearing. The driving cylinder (85) pushes by means of end pieces (84, 87) the auxiliary frame (77) which can slide upon the framework and which drives the protecting tube (57) into the tunnel. The hydraulic pressure hoses (82, 83) are taken through the hollow piston rod of the cylinder and arranged on both sides of the piston. The cylinder and the center part (76) are mounted on bearings to rotate inside the ring (91) provided with packings (92). The thurst bearing unit can move within the auxiliary frame which rests on rollers (90). The motor (79) rotates via chain (80) a chain wheel (81) fastened on the cylinder surface, the rotation

forces toward the tool in the drill head are transmitted to the hydraulic cylinder, which functions as thrust bearing, and can be detected as rise of pressure in the hyd-raulic system. To the driving cylinder, for instance adjusted pressure is transmitted over a pressure reduction valve, whereat the rise of cylinder (89) pressure leads to drop of set-value in the driving cylinder pressure regulating valve or it stops circulation of hydraulic fluid to the driving cylinder.

The control system can also be so arranged that for the actuators sensing tool affecting forces, a proper constant pressure is set and maintained through adjustment of cylinder pressure. This is a most advantageous method in cases where the drill head is provided with only one rotation producing tool .

This invention is not restricted to the embodiment desribed in the specification and in the drawings but it can be modified within the limits of the enclosed patent ^' claims. Pressure information from the tool is not necessarily taken all the way to the working pit along pressure hoses but intermediate electric or acustic wave based communication media can be used .