Page 66 - Wire Rope News & Sling Technology - December 2019
P. 66

INVENTOR’S CORNER
         continued from previous page
         and thus, surface pressure may be dispersed. Accordingly, the
         rope may maintain its roundness well, and the dimensional
         stability of the rope may also be maintained well.
           Also, as shown in figure 18, a diameter of each strand is
         formed to be small in this stated order: the diameter of the
         center strand 10, the diameter of the outer layer strand 30
         and the  diameter  of the  inner  layer strand  20,  and is  set
         to fall within the above-described range with respect to the
         diameter of the first circle 40 so that the fill factor may be
         maintained, as described above, as high as 64-67%, and at
         the same time, a rope diameter may be within a permissible
         tolerance range (EN12385-5) of the rope diameter. That is,
         the permissible tolerance range of the rope diameter is given
         as +2% from a rope nominal diameter, and in the rope for an
         elevator according to the present invention, the diameter of
         each strand is set to be in the above-described range, thereby
         satisfying the permissible tolerance range. When the diam-
         eter of each strand is out of the above-described range with   Figure 19: Drawing schematically illustrating figure 18  in terms of
         respect to the diameter of the first circle 40, the fill factor is   strands.
         less than 64% or exceeds 67%, and the rope diameter is out   tion rate decreases, whereas interlocking pressure between
         of the permissible tolerance range of the rope diameter.  strands increases, thereby degrading flexibility and decreas-
           Further, in the rope for an elevator according to the pres-  ing fatigue life.
         ent embodiment, the center strand 10, the inner layer strand   According to the embodiment of the present invention, as
         20 and the outer layer strand 30 are manufactured by a sin-  described above, spacing of the inner layer strands 20 is set to
         gle closing process, and thus, the fill factor is maintained as   range between 0.3% and 0.6%, and spacing of the outer layer
         high as in the above-described range. As shown in figure 19,   strands 30 is set to range between 0.5% and 1.0%. Thus, no
         when a gap formed by spacing apart adjacent inner layer   interlocking pressure may occur while the rope is used, and
         strands 20 is defined as a gap NG between the inner layer   structural instability due to excessive spacing may be solved.
         strands 20, and a diameter of a second imaginary circle 50   Accordingly, since spacing of the inner layer strands 20
         circumscribed around the inner layer strands 20 is defined   and the outer layer strands 30 is set to be in the above-de-
         as an inner layer rope diameter NR, the relationship of 0.3%   scribed range, the rope may have a high fill factor, thereby
         l (NG/NR)x100 l 0.6% is established. In this respect, (NG/  increasing breaking load and improving a safety factor of the
         NR)x100 is defined as spacing of the inner layer strands 20.  rope. Furthermore, the rope may have a high elastic coeffi-
           In addition, when a gap formed by spacing apart adjacent   cient and a low elongation rate. Due to the high elastic coeffi-
         outer layer strands 30 is defined as a gap OG between the outer   cient and the low elongation rate, vibration during driving of
         layer strands 30, and the diameter of the first imaginary circle   an elevator is minimized, and thus, riding comfort increases.
         40 circumscribed around the outer layer strands 30 is defined   Also, according to the embodiment of the present inven-
         as an outer layer rope diameter OR, the relationship of 0.5%   tion, a pitch of the center strand 10 is formed to be 6-8 times
         l (OG/OR)x100 l 1.0% is established. In this respect, (OG/OR)  as large as the diameter of the center strand 10, a pitch of
         x100 is defined as spacing of the outer layer strands 30.  the inner layer strand 20 is formed to be 8-10 times as large
           Spacing is an essential element of elevator ropes and has   as the diameter of the inner layer strand 20, and a pitch of
         a  lot  to  do with  a  structural  elongation  rate  and  fatigue   the outer layer strand 30 is formed to be 6.5-8.5 times as
         life.  When spacing  is  large,  the  structural elongation  rate   large as the diameter of the outer layer strand 30.
         increases,  and dimensional stability  deteriorates. On the   As the pitches are set to be in the above-described ranges,
         other hand, when spacing is too small, the structural elonga-  all the strands constituting the rope are subjected to load-
                                                              ing when the rope is subjected to loading, and accordingly, a
                                                              structural elongation rate of the rope decreases, and load dis-
                                                              tribution additionally becomes uniform. When the pitches are
                                                              out of the above-described ranges, load is relatively concen-
                                                              trated on one or two of the center strand 10, the inner layer
                                                              strand 20, and the outer layer strand 30, and the rest of them
                                                              is less subjected to loading, causing lack of uniformity in load
                                                              distribution. For example, load may be concentrated on the
                                                              center strand 10, and the inner layer strand 20 or the outer
                                                              layer strand 30 may be relatively less subjected to loading.
                                                              Lift crane with moveable counterweight
                                                              Pat. 10,457,530 U.S. class 1/1 Int. class B66C 23/76
                                                              Inventor: David J. Peck, Manitowoc, WI., Joseph R. Rucin-
                                                              ski, Manitowoc, WI.
                                                              Assignee: Manitowoc Cranes, LLC., Manitowoc, WI.
                                                               A lift crane includes a carbody; moveable ground engag-
                                                              ing members; a rotating bed rotatably connected to the car-
                                                              body; and a boom pivotally mounted on the rotating bed. The
         Figure 18: Cross-sectional view of a rope for an elevator.  crane is configured for assembly in at least two configura-

         66     Wire Rope News & Sling Technology   December 2019
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