Page 68 - Wire Rope News & Sling Technology - December 2019
P. 68

INVENTOR’S CORNER
         continued from previous page                         mounted on the boom butt, as shown in figure 22. If desired,
                                                              an additional hoist drum 19 can be mounted at the base of
                                                              boom 22, as shown in figures 22 and 23. The boom 22 may
                                                              comprise  a  luffing  jib  pivotally  mounted  to  the  top  of  the
                                                              main boom, or other boom configurations.
                                                               The counterweight  unit  35 is moveable with  respect to
                                                              the rest of the rotating bed 20. In the crane 10, the rotating
                                                              bed 20 includes a counterweight support frame 32, prefer-
                                                              ably in the form of a welded plate structure including a pair
                                                              of  spaced-apart  side  members  best  seen  in  figures  24-26.
                                                              The counterweight support frame  32 supports the move-



























                                                              Figure 23:  Side  elevation  view  of the  mobile lift  crane, with  the
                                                              counterweight in a rearward position.

         Figure 22:  Side  elevation  view  of the  mobile lift  crane, with  the   able counterweight unit 35 in a moveable relationship with
         counterweight  in a  mid-position, and showing  the crane  with its   respect to the counterweight support frame 32. The coun-
         boom and live mast.                                  terweight support frame 32 comprises a sloped surface pro-
                                                              vided by flanges 39 that the counterweight unit 35 moves
           A boom hoist system on crane 10 allows the angle of the
         boom 22 relative to the plane of rotation of the rotating bed 20   on, that surface sloping upwardly compared to the plane of
         to be changed in the crane 10, the boom hoist system includes   rotation between the rotating bed and the carbody as the
         rigging connected between the rotating bed 20, the mast 28   counterweight support frame extends rearwardly.
         and the boom  22. The boom hoist system includes a boom   The counterweight tray 33 includes rollers 37 which rest
         hoist drum and boom hoist line reeved between a sheave set   on the flanges 39 welded to the plate structure of the support
         on the mast and a sheave set on the rotating bed. The mast   frame. The rollers 37 are placed on the top of the counter-
         28 is pivotally connected to the rotating bed and the boom   weight tray 33 so that the tray 33 is suspended beneath the
         hoist rigging between the mast and the boom comprises only   counterweight support frame 32. In the crane 10, the coun-
         fixed length members in the form of two sets of pendants 25   terweight support frame constitutes the rearmost fixed por-
         (only one of which can be seen in the side view) connected   tion of the rotating bed. Further, the counterweight support
         between the mast 28 and the top of the boom 22. In addition   frame 32 is supported on the rotating bed 20 in a fashion
         the boom hoist rigging includes multiple parts of boom hoist   such that the moment generated by the counterweight unit
         line 27 between sheaves 23 on the rotating bed and sheaves
         on the second end of mast 28. A boom hoist drum 21 on the
         rotating bed can thus be used to take up or pay out boom hoist
         line 27, changing the angle of the live mast 28 with respect
         to the rotating bed, which in turn then changes the angle of
         the boom 22 with respect to the rotating bed 20. (Sheaves 23
         and drum 21 are not shown on figures 24-26 for sake of clar-
         ity.) Alternatively, the mast 28 could be used as a fixed mast
         during normal crane operation, with boom hoist line running
         between an equalizer and the top of the mast to change the
         angle between the mast and the boom.
           A load hoist line 24 for handling a load extends from the
         boom  22, supporting a hook  26. The rotating bed  20 may
         also include other elements commonly found on the mobile
         lift crane, such as an operator’s cab and whip line drum 29.   Figure 24:  Partial perspective  view, with  the  counterweight in a
         The load hoist drum 13 for the hoist line 24 is preferably   rearward position.
         68     Wire Rope News & Sling Technology   December 2019
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