Page 60 - Wire Rope News & Sling Technology - August 2018
P. 60

continued from previous page                         and 12, the wire ropes  12,  14,  16,  18 extend between a
                                                              hoisted object 20 and a counterweight 24 and contact an
                                                              electrically connecting sheave 22. In the embodiment illus-
                                                              trated in figure 13, the system 10 is used to monitor four
                                                              wire ropes 12, 14, 16, 18 in a 2:1 roping configuration. In
                                                              figure 13, the wire ropes 12, 14, 16, 18 extend between first
                                                              and second hoistway ceiling mounts 23, 25, and contact an
                                                              electrically connecting sheave 22, as well as several electri-
                                                              cally non-connecting sheaves 27, 29, 31.
                                                               In figure 13, first and second electrically non-connecting
                                                              sheaves 27, 29 are connected to a hoisted object 20, and a
                                                              third electrically non-connecting sheave 31 is connected to a
                                                              counterweight 24. In other embodiments, the system 10 may
                                                              be used to monitor greater than or less than four wire ropes
                                                              12, 14, 16, 18 and/or the system 10 may be used to monitor
                                                              wire ropes 12, 14, 16, 18 that are arranged in another roping
         Figure 10: Schematic circuit diagram for elevator belt fault detection.
                                                              configuration.
         detection unit  52 in  the form of  an AC voltage, or alter-  The wire ropes 12, 14, 16, 18 each include a plurality of
         natively  a  DC  voltage  source,  and  the  bridge  circuit  58   electrically conductive wire strands that are wound together
         outputs a signal voltage via output leads  56 to the fault   in a known manner to form the wire ropes 12, 14, 16, 18.
         detection unit  52. The fault detection unit  52 compares   The wire strands may be made of steel, or another accept-
         the excitation voltage to the signal voltage and evaluates   able material. Referring to figures 11 and 13, the wire ropes
         an electrical impedance and/or electrical resistance of the   12, 14, 16, 18 each include a body 26 that extends between
         belt 16. The measurements are dynamic such that changes
         in complex impedance or electrical resistance are evalu-
         ated by the detection unit 52 and are indicative of wear,
         fretting and wire breakage in the cords 32 of the belt 16.
         Configuring the cords 32 as a bridge circuit 58 suppresses
         noise from electromagnetic interference (EMI), tempera-
         ture variation along a length of the cords 32, and tensile
         load variation along each cord 32. The connection scheme
         increases the total resistance of the circuit 58 and reduced
         the interrogating current through the cords  32, thus im-
         proving signal to noise ratio. Further, since the cords 32
         are all interconnected in the circuit 58, all of the cords 32
         are monitored simultaneously, thus reducing a number of
         required measurement channels.

         System and method for monitoring wire ropes
         Pat. 9,862,572 U.S. class B66B 7/1223 Int. class B66B 7/12
         Inventor: Richard N. Fargo, Plainville, CT.
         Assignee: Otis Elevator Co., Farmington, CT.
           This patent presents a system and method for monitoring
         a  first  wire  rope  and  second  wire  rope.  The  first  and  sec-  Figure 11: Schematically illustrates an embodiment of the system and
         ond wire ropes each include a contact portion that contacts   method for positioning wire ropes.
         a sheave, a first end portion, and a monitored portion that
         extends between the contact portion and the first end por-  first and second end portions 28, 30 of the wire rope 12, 14,
         tion. The sheave electrically connects the contact portions   16, 18. In the embodiment illustrated in figures 11 and 12,
         of  the  first  and  second  wire  ropes.  The  system  includes  a   the first end portions 28 of the wire ropes 12, 14, 16, 18 are
         controller that is electrically connected to each of the first   connected to the hoisted object 20, and the second end por-
         and second wire ropes to form a circuit with the monitored   tions 30 of the wire ropes 12, 14, 16, 18 are connected to the
         portions of the first and second wire ropes. The controller   counterweight 24. In the embodiment illustrated in figure
         selectively applies a signal to the monitored portions of the   13, the first end portions 28 of the wire ropes 12, 14, 16, 18
         first  and  second  wire  ropes  and  determines  an  electrical   are connected to the first hoistway ceiling mount 23, and the
         characteristic  thereof.  The  controller  uses  the  determined   second end portions 30 of the wire ropes 12, 14, 16, 18 are
         electrical characteristic to determine a condition of the first   connected to the second hoistway ceiling mount 25.
         and second wire ropes.                                The body 26 of each wire rope 12, 14, 16, 18 is electrically
           Referring  to  figures  11-13,  the  present  disclosure  de-  uninsulated; e.g., along the body 26, the wire strands of the
         scribes embodiments of a system 10 for monitoring a con-  wire rope 12, 14, 16, 18 may be exposed. The first and sec-
         dition of a plurality of wire ropes 12, 14, 16, 18. The wire   ond end portions 28, 30 of each wire rope 12, 14, 16, 18 are
         ropes 12, 14, 16, 18 aid in hoisting an object 20, and they   electrically insulated; e.g., the first and second end portions
         contact an electrically connecting sheave 22. Aspects of the   28, 30 may be encased in a polyurethane jacket. The body 26
         present invention are not limited to the embodiment shown   of each wire rope 12, 14, 16, 18 includes a contact portion 32
         in figures 11-13. In the embodiment illustrated in figures   that is in contact with the electrically connecting sheave 22.
         11 and 12, the system 10 is used to monitor four wire ropes   The position of the contact portions 32 on the wire ropes 12,
         12, 14, 16, 18 in a 1:1 roping configuration. In figures 11   14, 16, 18 changes as the wire ropes 12, 14, 16, 18 are moved

         60     Wire Rope News & Sling Technology   August 2018
   55   56   57   58   59   60   61   62   63   64   65