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BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a shield tunneling machine that excavates a tunnel or other similar passage while crushing obstacles encountered during excavation.  
         [0002]     There has heretofore been known a shield tunneling machine having water jet spray nozzles provided on a cutter head that is provided at the forward end of a shield body in the excavation direction and rotatable relative to the shield body to excavate a tunnel or the like while crushing obstacles encountered during excavation [see Japanese Patent Application Unexamined Publication (KOKAI) No. Hei 10-280880].  
         [0003]     However, the conventional shield tunneling machine still has a problem to be solved. That is, because the spray nozzles are immovable, it is impossible to properly control the spray nozzles according to the size and configuration of each particular obstacle encountered during excavation, and hence difficult to break it into easily removable pieces with high cutting quality.  
       SUMMARY OF THE INVENTION  
       [0004]     In view of the above-described circumstances, an object of the present invention is to provide a shield tunneling machine capable of breaking obstacles effectively with high cutting quality by properly controlling movable abrasive jet spray nozzles according to the size and configuration of each particular obstacle.  
         [0005]     To attain the above-described object, the present invention provides a shield tunneling machine including a shield body and a cutter head provided at the forward end of the shield body in the excavation direction. The cutter head is rotatable relative to the shield body. An abrasive jet spray nozzle for spraying abrasive jet water is movably provided on the cutter head.  
         [0006]     Preferably, the abrasive jet spray nozzle is radially movable and thus capable of cutting an obstacle encountered during excavation into a round shape and further cutting it radially.  
         [0007]     Preferably, the abrasive jet spray nozzle is oscillatable to allow the spray direction to be changed.  
         [0008]     Preferably, a slurry is mixed in the abrasive jet water sprayed from the abrasive jet spray nozzle.  
         [0009]     Preferably, a fixed spray nozzle for spraying high-pressure jet water is provided on the cutter head, and the obstacle is searched for on the basis of reflected sound of high-pressure jet water sprayed from the fixed spray nozzle.  
         [0010]     The fixed spray nozzle may be used for cleaning cutter bits provided on the cutter head.  
         [0011]     Preferably, cutter bits are provided in proximity to the abrasive jet spray nozzle to protect it.  
         [0012]     Preferably, a drive mechanism for the abrasive jet spray nozzle is a hydraulic cylinder drive system comprising a cylinder and a piston rod.  
         [0013]     The drive mechanism for the abrasive jet spray nozzle may be a threaded rod drive system comprising a drive motor and a threaded rod.  
         [0014]     The drive mechanism for the abrasive jet spray nozzle may be a rack-and-pinion drive system comprising a drive motor, a rack and a pinion.  
         [0015]     Preferably, at least two radially spaced abrasive jet spray nozzles are provided as the above-described abrasive jet spray nozzle. Each abrasive jet spray nozzle is supported by a nozzle head and radially movable.  
         [0016]     Preferably, the nozzle head is provided in a radially extending enclosure. The enclosure is always supplied with cleaning water. The nozzle head is immersed in the cleaning water and radially movable.  
         [0017]     Preferably, each abrasive jet spray nozzle is swivelable.  
         [0018]     Preferably, the swivelable abrasive jet spray nozzle is decentered with respect to the swivel axis.  
         [0019]     In the shield tunneling machine according to the present invention, the abrasive jet spray nozzles are movable relative to the cutter head. Therefore, obstacles encountered during excavation can be broken effectively with high cutting quality by properly controlling the movable abrasive jet spray nozzles according to the configuration and size of each particular obstacle.  
         [0020]     Thus, according to the present invention, abrasive jet spray nozzles are provided on the cutter head. While the cutter head is being rotated, abrasive jet water is sprayed from the nozzles to cut an obstacle into ring shapes. Then, while the abrasive jet spray nozzles are being moved radially, abrasive jet water is sprayed therefrom, thereby breaking a large obstacle into fan-shaped pieces.  
         [0021]     The above and other objects, features and advantages of the present invention will become more apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]      FIG. 1  is a fragmentary longitudinal sectional view of the shield tunneling machine according to an embodiment of the present invention, showing a shield body including a cutter head.  
         [0023]      FIG. 2  is a front view of the cutter head shown in  FIG. 1 .  
         [0024]      FIG. 3  is a diagram showing a hydraulic cylinder drive mechanism for abrasive jet spray nozzles shown in  FIG. 2 , in which (a) shows a state where a nozzle head is positioned radially outward, and (b) shows a state where the nozzle head is positioned radially inward.  
         [0025]      FIG. 4  is a diagram showing in detail the arrangement of the nozzle head shown in  FIG. 2 .  
         [0026]      FIG. 5  is a diagram showing in detail the arrangement of the abrasive jet spray nozzle shown in  FIG. 4 .  
         [0027]      FIG. 6  is a schematic view for explaining the operation of the abrasive jet spray nozzles shown in  FIG. 2 .  
         [0028]      FIG. 7  is a diagram showing a threaded rod drive mechanism as another example of the abrasive jet spray nozzle drive mechanism shown in  FIG. 2 .  
         [0029]      FIG. 8  is a diagram showing a rack-and-pinion drive mechanism as another example of the abrasive jet spray nozzle drive mechanism shown in  FIG. 2 .  
         [0030]      FIG. 9  is an explanatory view showing an arrangement in which the nozzle head shown in  FIG. 2  is reciprocatably immersed in cleaning water.  
         [0031]      FIG. 10  is a schematic view showing various examples of the layout of nozzle heads shown in  FIG. 2 , in which: (a) shows an arrangement in which nozzle heads are provided on both sides, respectively, of one mounting plate, and a fixed spray nozzle is provided on this mounting plate; (b) shows an arrangement in which one nozzle head is installed on one mounting plate, and the other nozzle head is installed on the other mounting plate, and moreover, a fixed spray nozzle is provided on the first-mentioned mounting plate; (c) shows an arrangement in which nozzle heads are provided on one mounting plate at respective positions opposite each other across the rotating shaft, and a fixed spray nozzle is installed on this mounting plate; and (d) shows an arrangement in which nozzle heads are provided on one mounting plate at respective positions opposite each other across the rotating shaft, and a fixed spray nozzle is installed on the other mounting plate.  
         [0032]      FIG. 11  is a conceptual view showing an example in which the abrasive jet spray nozzle is provided swivelably.  
         [0033]      FIG. 12  is a conceptual view showing another example in which the abrasive jet spray nozzle is provided swivelably and decentered with respect to the swivel axis. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]     Embodiments of the shield tunneling machine according to the present invention will be described below in detail with reference to the accompanying drawings.  
         [0035]      FIG. 1  is a fragmentary longitudinal sectional view of the shield tunneling machine according to an embodiment of the present invention, showing a shield body  1  of the shield tunneling machine. In  FIG. 1 , the shield body  1  includes a cutter head  2  having a rotating shaft  3 . The shield body  1  further includes a slurry discharge pipe  4 ′. The cutter head  2  is provided at the forward end of the shield body  1  in the excavation direction. As shown in  FIG. 2 , the cutter head  2  has a ring plate  3 ′. The ring plate  3 ′ has mounting plates  4  and  5  secured thereto. The mounting plates  4  and  5  extend diametrically of the ring plate  3 ′ and intersect each other perpendicularly.  
         [0036]     The mounting plates  4  and  5  intersect each other at the rotating shaft  3 . The mounting plates  4  and  5  are provided with center bits  6 , cutter bits  7 , leading bits  8  and trimming bits  9  appropriately.  
         [0037]     In this embodiment, the mounting plate  4  is provided with nozzle heads  10  on both lateral sides thereof. Each nozzle head  10  has abrasive jet spray nozzles  10   a.  Cutter bits  11  are provided at both sides of each abrasive jet spray nozzle  10   a  to protect it.  
         [0038]     The nozzle head  10  is driven by a drive mechanism (drive system)  10 A as shown in parts (a) and (b) of  FIG. 3 . In this embodiment, the drive mechanism  10 A is a hydraulic cylinder drive system comprising a piston rod  12  and a hydraulic cylinder  13 . The nozzle head  10  is secured to one end of the cylinder  13  through a mounting head  14 . The cylinder  13  is movable in reciprocating directions along the piston rod  12  in response to switching between IN and OUT of oil pressure.  
         [0039]     The piston rod  12  is formed with a passage  12   a  for supplying ultra-high pressure water from the rotating shaft  3 . The passage  12   a  communicates with the abrasive jet spray nozzles  10   a  through a supply pipe  12   b.    
         [0040]     The piston rod  12  has a space  12   c  for allowing the supply pipe  12   b  to advance and retract in the piston rod  12 .  FIGS. 4 and 5  show the arrangement of the nozzle head  10  in detail. The nozzle head  10  is connected with supply pipes  15  for supplying a slurry (starch-based cutting fluid). As shown in  FIG. 5 , abrasive jet water  10   e  is sprayed with air  10   d  surrounding it. In this embodiment, three abrasive jet spray nozzles  10   a  are provided for each nozzle head  10 , as shown schematically in  FIG. 6 . The abrasive jet spray nozzles  10   a  are spaced in the radial direction of the cutter head  2 , in which the mounting plate  4  extends. It should be noted, however, that one or two abrasive jet spray nozzles  10   a  may be provided for each nozzle head  10 .  
         [0041]     As shown in  FIG. 1 , the cutter head  2  is rotated about the rotating shaft  3  by a drive motor  17 . While the cutter head  2  is rotating, abrasive jet water  10   e  is sprayed from the abrasive jet spray nozzles  10   a,  thereby allowing an obstacle  18  encountered during excavation to be cut in ring shapes. Further, by moving the abrasive jet spray nozzles  10   a  radially at high speed, the obstacle  18  cut in ring shapes can be cut radially.  
         [0042]     With the abrasive jet spray nozzles  10   a,  because a slurry is mixed into high-pressure jet water, it is possible to cut and break the obstacle  18  efficiently while minimizing the wear of the abrasive jet spray nozzles  10   a.    
         [0043]     The drive mechanism  10 A for the abrasive jet spray nozzles  10   a  according to the present invention is not limited to that shown in  FIG. 3 . The drive mechanism  10 A may be arranged as shown in the following modifications.  
         [heading-0044]     (First Modification)  
         [0045]     For example, as shown in  FIG. 7 , the nozzle head  10  is secured to the forward end of a threaded rod  19 , and a gear  20  is provided on the rear end of the threaded rod  19 . An output shaft  22  of a drive motor  21  is meshed with the gear  20 . With this drive mechanism, the rotation of the drive motor  21  is converted into forward or backward movement of the threaded rod  19 , thereby moving the nozzle head  10  back and forth in the radial direction.  
         [heading-0046]     (Second Modification)  
         [0047]     For example, as shown in parts (a) and (b) of  FIG. 8 , the nozzle head  10  is provided with a rack  23 , and a pinion  24  that is meshed with the rack  23  is mounted on an output shaft  26  of a drive motor  25 . With this drive mechanism, the rotation of the drive motor  25  is converted into forward or backward movement of the rack  23 , thereby moving the nozzle head  10  back and forth in the radial direction.  
         [heading-0048]     (Third Modification)  
         [0049]     It is desirable from the viewpoint of protecting the drive mechanism  10 A from sludge and other contamination that the nozzle head  10  according to the present invention should be arranged as shown in  FIG. 9 . That is, a radially extending vessel  27  is provided on the mounting plate  4 , and cleaning water  28  is always supplied into the vessel  27 . The inside of the vessel  27  is held at a positive pressure, and the nozzle head  10  is immersed in the cleaning water  28 .  
         [0050]     With the above-described arrangement, it is possible to prevent adhesion of contamination to the drive mechanism  10 A. Hence, it is possible to allow the nozzle head  10  to reciprocate smoothly and to minimize the incidence of failure. It should be noted that in  FIG. 9  reference numeral  29  denotes a nozzle cover, and reference numeral  30  denotes seal rings.  
         [heading-0051]     (Fourth Modification)  
         [0052]     In the foregoing embodiment, the nozzle heads are provided on both lateral sides of the mounting plate  4  as shown schematically in (a) of  FIG. 10 . However, the present invention is not necessarily limited to the above. The arrangement may be such that, as shown schematically in (b) of  FIG. 10 , one nozzle head  10  is installed on the mounting plate  4 , and the other nozzle head  10  is installed on the mounting plate  5 , which extends in a direction perpendicular to the mounting plate  4 . The arrangement may also be such that, as shown schematically in (c) and (d) of  FIG. 10 , the nozzle heads  10  are provided at respective positions opposite each other across the rotating shaft  3 .  
         [0053]     Further, the arrangement may be such that, as shown in (a) to (c) of  FIG. 10 , a fixed spray nozzle  31  that sprays high-pressure jet water is provided on the mounting plate  4 . Sound generated by spraying of high-pressure jet water from the fixed spray nozzle  31  and reflected from the obstacle  18  is analyzed with an oscilloscope. In this way, the presence of the obstacle  18  is searched for, and the nozzle heads  10  are moved based on the result of the analysis.  
         [0054]     The fixed spray nozzle  31  may be provided on the mounting plate  5 , which intersects the mounting plate  4  perpendicularly, as shown in (d) of  FIG. 10 .  
         [0055]     Although in this embodiment the fixed spray nozzle  31  is used to search for an obstacle  18 , it may be used for cleaning the cutter bits  7 .  
         [heading-0056]     (Fifth Modification)  
         [0057]     Although in the foregoing embodiment the nozzle heads  10  are radially movable, the arrangement may be as follows. As shown in  FIG. 11 , the nozzle head  10  is mounted on a hydraulic rotary actuator  32 . The spray direction O 2  of the abrasive jet spray nozzle  10   a  is set obliquely to the swivel axis O 1  of the nozzle head  10 . Thus, the spray direction O 2  is changed by swiveling the nozzle head  10 . The arrangement may be as shown in  FIG. 12 . The abrasive jet spray nozzle  10   a  is provided swivelably and decentered with respect to the swivel axis O 1  to broaden the range of changes in the spray direction O 2  of abrasive jet water.  
         [0058]     The shield tunneling machine according to the present invention is usable in construction work of tunnels, underground passages, trenches for piping of water supply and sewerage systems, manholes, and so forth.  
         [0059]     It should be noted that the present invention is not limited to the foregoing embodiments but can be modified in a variety of ways.

Summary:
A shield tunneling machine has a shield body and a cutter head rotatably provided at the forward end of the shield body in the excavation direction. Abrasive jet spray nozzles for spraying abrasive jet water are movably provided on the cutter head. Obstacles encountered during excavation can be broken efficiently with high cutting quality by properly controlling the movable abrasive jet spray nozzles according to the size and configuration of each particular obstacle.