Page 61 - Wire Rope News & Sling Technology - February 2020
P. 61

INVENTOR’S CORNER
         is much less than the traction wheel 2, it can greatly reduce   Adjustable length tensioning member
         the cost of the whole elevator system. In this embodiment,   Pat. 10,479,657 U.S. class 1/1 Int. class B66C 23/00
         the middle-drive type means that the tractor 2 is installed   Inventor: Ian M. Moore, Manitowoc, WI.
         between the lift car 1 and the guide pulley 4.       Assignee: Manitowoc Crane Companies, LLC., Manitowoc, WI.
           In elevator field, disposing a tractor above a guide pulley   This patent presents an adjustable length tensioning
         is generally conventional practice, because it is in line with   member that comprises a rope, a first connector on the rope,
         the principle of general structure mechanics and can provide   a second connector on the rope, and a plurality of connec-
         a larger mechanical drive force to the lift car. Under this ap-  tion points between the first connector and the second con-
         proach, the wire rope that connects the tractor and the guide   nector. The plurality of connection points have a diameter
         pulley has to use either of full-wound or semi-wound type to   greater than a diameter of the rope. The rope may be passed
         wind, wherein, the full-wound type is that each wire rope   through a socket coupled to a first crane component and one
         winds around the tractor twice, therefore two correspond-  of the connectors on the rope is coupled to a second crane
         ing  rope  groove  are  needed; the  semi-wound  type is  that   component. One of the plurality of connection points engages
         each wire rope winds around the tractor once, therefore only   a seat on the socket to tension the rope between the socket
         one corresponding rope groove is needed. But both the two   and the connection point.
         types have a defect that the tractor bears the most weight of   The term “crane suspension  assembly section” refers  to
         the lift car and the counterweight device, which causes the   sections that are connected together to form a suspension as-
         working life of the tractor is shortened greatly.    sembly for a crane. Examples of crane suspension assembly
           The practice of disposing the tractor below the guide   sections include a) sections, sometimes called strap sections,
         pulley used  by the present invention, theoretically, goes   of the backstay between the boom top and the equalizer or
         against the conventional mechanics principle, and to over-  live mast; b) sections of the backstay between a boom butt
         come this  problem, the present  invention  uses  a newly   and a jib strut; c) sections of the backstay between a jib strut
         winding type of the wire rope between the tractor and the   and a jib top, and d) counterweight strap sections between a
         guide pulley.  In  particular,  corresponding  to the  struc-  mast top and a counterweight. Besides strap sections, which
         ture that the tractor is disposed below the guide pulley,   are traditionally elongated rigid metal members with a head
         the wind type of the wire rope 3 of the present invention   on each end with a hole there through, sometimes wire rope
         uses mixing wind type of combination of full-wound and   pendants or even carbon fiber tension members are used to
         semi-wound, wherein the full-wound increases the contact                              continued on next page
         area between the wire rope 3 and the tractor 2 as well as
         the guide pulley 4, to improve driving force, and the semi-
         wound improves the safety performance, because the semi-
         wound type needs only one corresponding rope groove, in
         the case that the amounts of the rope groove disposed are
         fixed, the semi-wound type can increase the amount of the
         wire rope contrary to the full-wound type, and in the el-
         evator field, the more the amount of the wire rope are, the
         larger the safety factor is.
           In the selected embodiment, the tractor 2 locates at the
         lower right of the guide pulley 4, and at this time, the lift
         car 1 locates at the lower right of the entire elevator system,
         and the counterweight device 5 locates at the lower left of
         the entire elevator system. Furthermore, the angle between
         the lines between the traction wheel 6 center and the guide
         pulley 4 center and the horizontal plane is b, and the range
         of the b is between 0°-90°. In the optimized embodiment, the
         range value of the b is 40°-75°. The value of b directly deter-
         mines the load level of the tractor 2. It can be known from
         figure 4 that the tractor 2 in the embodiment is located at
         the lower right of the guide pulley 4, and the value of b is 56°
         for example; and the lift car 1 is located below the tractor 2.
         In this embodiment, the best value of the b is 45°.
           The tractor 2 of the elevator as a drive part is installed
         between the lift car 1 and the guide pulley 4; the lift car 1 is
         hung by one end of the wire rope 3 after the end of the wire
         rope 3 passing through the guide pulley 4 and the traction
         wheel 6 on the tractor 2; and the counterweight device 5 is
         hung by the other end of the wire rope 3; the traction force
         caused by the friction between the wire rope 3 and the wheel
         groove of the traction wheel 6 drives the lift car 1 to run up
         and down. Through the middle arrangement of the tractor
         2, the guide pulley 4 bears the majority of the weight of the
         lift car 1 and the counterweight device 5, and the tractor 2
         bears only the minority of the weight of the lift car 1 and the
         counterweight device 5; thus, it can effectively reduce the
         load borne by the tractor 2 and greatly improve the service   Figure 5: Illustrates a side view of an embodiment of a mobile lift
         life of the tractor 2.                               crane having a live mast.

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