Ring cutter for tunnel drilling in rock
BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     The present invention is related to a ring cutter for tunnel drilling in rock, which cutter is secured to the rotation body of the cutter ring with a dovetail shaped cross section. 
     B. Description of the Prior Art 
     Tunnel drilling machines or full face machines are used with idle journalled ring cutters distributed on the surface of the cutter head, each ring thereby being subjected to strong wear as well as some deformation. Replacing such cutter rings in known embodiments, requires dismantling the cutter to remove the cutter ring itself. Some known cutter rings comprise several segments, however, this configuration is not practical in use of certain rock types. Other configurations use complete rings are used which therefore lead to relative expensive and time consuming replacement work which also for the operator also means requires heavy working. 
     SUMMARY OF THE INVENTION 
     With the cutter rings according to the present invention, a cutter ring in two parts is provided which is suitable for practical use and additionally may be replaced within a very short time. This is achieved with the cutter ring according to the present invention as defined with the features of the accompanying claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, FIG. 1, discloses an axial section of a cutter ring bearing and FIG. 2 discloses a side view of the bearing on FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A rotational body 2 is journalled on a shaft 6 secured to the cutter head of the drilling machine. The outer circumference of the rotational body 2 is provided with a dovetail groove which in one side is expanded to a key way. In the dovetail groove are arranged diametrically opposed, two radially inwardly protruding pins 6, adapted for receipt in corresponding hole 9 in each cutter ring half 1. The holes 9 are arranged in the middle of the cutter ring halves 1. By inserting the two cutter ring halves 1 in the dovetail groove and with the pin 6 protruding into the hole 9, the cutter ring halves 1 may be displaced axially by a corresponding shape of the holes 9 in such a way that the cutter ring halves 1 may abut against the one half of the dovetail groove in the rotational body 2. Between the cutter ring halves 1, two gaps 3 with a dimension between 1.5 and 8 mm, preferably between 2 and 4 mm are provided. The gaps 3 have such a size that the cutter ring halves 1 can be manufactured by simple cutting of a complete cutter ring and the gap thereby is not that large to allow detrimental strokes will occur on the edge, as well known to be the case by larger gaps. On the other hand the gaps enable the cutter ring 1 to be deformed to a certain degree without closing the gap and thereby incur internal stress. 
     The cutter ring halves 1 are secured to the rotational body 2 by clamping rings 4 comprising two equal halves where the dimensions 8 between the two clamping ring halves preferably are offset 30° in relation to the gaps 3. The clamping rings 4 preferably have a wedge shaped cross section where one of the side surfaces is abutting against the cutter ring 1 and the other surface is abutting against a corresponding inclined surface in the rotational body 2. 
     The cutter ring is secured to the rotational body 2 by bolts 5 in axial planes 7 being offset 60° in relation to each other, and with the gaps 3. 
     By tightening of the bolt 5, the cutter ring 1 is pressed against one of the inclines surfaces of the dovetail groove in the rotational body 2, thereby secured with sufficient force. 
     The two pins 6 ensures that the cutter ring 1 will not rotate in relation to the rotation body 2 and the clamping ring 4. 
     Dismantling and assembling of a new cutter ring 1 is made very easy by removing the bolts 5 and the two halves of the clamping ring 4. Thereafter the cutter ring halves 1 easily can be replaced and the two halves of the clamping ring are again tightened by the bolts 5 with a force large enough to fix the cutter ring 1 to the rotation body 2.