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         the drill bit constant. The drilling head 5 comprises a car-
         riage 51, adapted to slide along suitable guides 35 provided
         in mast 3, both on the fixed portion 30 and on the mobile por-
         tion 32, so as to be able to slide along the entire longitudinal
         extension of mast 3.
         Cable with optical fiber for prestressed concrete
         Pat. 9,575,271 U.S. class G01B 11/16 Int. class G02B 6/44
         Inventor: Kenichi Fuse, Hadano, JP.
         Assignee: EMPIRE TECHNOLOGY DEVELOPMENT LLC,
         Wilmington, DE.
           A reinforcing cable for a prestressed concrete structure is
         disclosed. The cable has an optical fiber entwined between   Figure 6: Side view of an embodiment of a cable for externally
         the twisted wire ropes that form the cable. The optical fi-  reinforcing prestressed concrete.
         ber facilitates in situ monitoring of cable integrity by com-  plaited, or twisted around the core rope 20. Of course, the
         paring optical signal transmission over time. A reinforcing   total number of ropes N, the number of core ropes and the
         cable  is  disclosed  in  accordance  with  one  embodiment  of   number of outer ropes may vary. The illustrated embodi-
         the disclosure. The cable includes one or more wire ropes   ment includes a total of seven ropes, with one core rope 20
         twisted together, each wire rope comprising a plurality of   and six outer ropes 30. If the total number N of wire ropes is
         wire strands twisted together, and one or more optical fi-  seven and the diameter of each wire rope is approximately
         bers entwined with and contacting at least some of the one   11.1 mm, an outside diameter of the reinforcing cable 2 will
         or more twisted wire ropes, each optical fiber comprising a   be approximately 33.3 mm. Alternatively, for example, if the
         core configured to transmit an optical signal and a cladding   total number N of wire ropes is nineteen and the diameter
         around the core.                                     of each wire rope is approximately 9.5 mm, an outside di-
           In some embodiments, the cable may further contain a   ameter of the reinforcing cable 2 will be approximately 47.5
         plastic coating surrounding the cable. In some embodiments,   mm. Of course it is understood that the diameter of the wire
                                                              ropes themselves, and consequently, the outside diameter of
                                                              the reinforcing cable may vary.
                                                               In some embodiments, and with reference to figures 5 and
                                                              6, each of the core  20  and/or  outer  wire  ropes  30 may be
                                                              formed from a plurality of wire strands 40 twisted or braided
                                                              together. Each wire strand may have a straight solid-core
                                                              wire or a twisted multi-stranded wire in order to produce
                                                              increased strength and flexibility. The wire strand can be
                                                              made, for example, of PC steel wire, PC twisted steel wire,
                                                              PC hard steel wire  and combinations thereof.  The  wire
                                                              strands 40 and/or the wire rope 30 may be coated in a plas-
                                                              tic, so that the wire strand may be insulated from undesir-
                                                              able moisture, salt, acid or alkaline substances and electric-
                                                              ity which may cause corrosion. Figures 6 and 7 illustrate a
                                                              plastic coating 32 around the outer surface of the wire rope
                                                              30. This plastic may be selected from polyolefins, nylon, Tef-
                                                              lon and combinations and copolymers thereof. Further, the
         Figure 5:  Cross-sectional  view  of an embodiment  of a cable for   polyolefin may be selected from polyethylene, polypropylene,
         externally reinforcing prestressed concrete.         polybutylene and copolymers thereof.  The plastic can fur-
                                                              ther include carbon black, antioxidant, or other UV absorb-
         each wire strand may include a straight solid-core wire or a   ing or reflecting material, and combinations thereof, in order
         twisted multi-stranded wire. In some embodiments, at least   to prevent oxidization due to sunlight.
         one wire strand may be coated in a plastic. In some embodi-
         ments, the plastic may be selected from the group consist-
         ing of polyolefins, nylon, Teflon and copolymers thereof. In
         some embodiments, the polyolefin may be selected from the
         group consisting of polyethylene, polypropylene, polybutyl-
         ene and copolymers thereof. In some embodiments, the plas-
         tic may further contain carbon black, an antioxidant, or a
         combination thereof. In some embodiments, the plurality of
         wire strands may be selected from the group consisting of
         PC (Prestressed Concrete) steel wire, PC twisted steel wire,
         PC hard steel wire, and any combination thereof.
           With reference to figures 5 and 6, an embodiment of a rein-
         forcing cable is illustrated. Figure 5 is a cross-sectional view
         showing a number of N wire ropes (N: a natural number) are
         arranged with a center or core rope 20 and (N-1) outer ropes
         30 surrounding the core rope 20. As can be appreciated from
         figures  5  and  6,  the  outer  ropes  30  may  be  laid,  braided,   Figure 7: Cross-sectional view of one of the outer wire ropes.

         54     Wire Rope News & Sling Technology   June 2017
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