Patent Publication Number: US-6341669-B1

Title: Pivoting termination for elevator rope

Description:
FIELD OF THE INVENTION 
     This invention pertains to the field of rope (cable) hitches and terminations, and in particular, to a pivoting termination for an elevator rope. 
     BACKGROUND OF THE INVENTION 
     An elevator is a hoisting and lowering mechanism equipped with a car or platform which moves in guides in a vertical direction. Electric elevators are suspended and moved by a series of pulleys (sheaves) and cables (ropes). In a typical arrangement, a wire rope is reeved over a number of sheaves, terminating in a hitch on the top and bottom of the car. Care is typically taken during the installation to mount the various sheaves in the machine room or on the car in such a manner as to ensure only vertical strain is applied to the wire ropes terminating in hitches. This reduces metal fatigue on the wire rope that would occur if subjected to horizontal bending forces. 
     Coated steel belts (CSB&#39;s) have been developed which are strong enough to replace the traditional wire cables used with elevators. These CSB&#39;s permit sheave and hitch arrangements that were not practical when using wire ropes. In an arrangement where the CSB hitch or termination is subjected to horizontal forces as well as vertical forces, metal fatigue is a concern. 
     SUMMARY OF THE INVENTION 
     Briefly stated, a pivoting hitch for an elevator rope includes a horizontal shaft or ball having a circular base and a flat top. The shaft or ball rests on a seat. An elevator rope is connected to a rod which passes through a hole in the shaft or ball and is suspended on the flat part of the shaft or ball by a spring. The shaft is used when multiple ropes are used to suspend an elevator car. When used with an overslung or underslung elevator car suspension, the pivoting hitch keeps the rope angles on both sides of the elevator car the same. 
     According to an embodiment of the invention, a pivoting hitch for an elevator rope includes a shaft being shaped as a right cylindrical prism, with a base having a circular arc joined at both ends by a straight line whereby the shaft has a flat portion and a rounded circular portion; at least one hole through the shaft, the at least one hole being substantially perpendicular to the flat portion; the rounded circular portion of the shaft resting on a seat, wherein a shape of the seat that makes contact with the shaft is congruent to the rounded circular portion of the shaft; the seat resting on a lower hitch plate; the lower hitch plate having at least one hole therein; at least one rod passing through the at least one hole in the lower hitch plate, through the at least one hole of the shaft, and through at least one spring; and an end of the at least one rod being connected to a termination for a rope, and another end of the at least one rod being connected to the spring. 
     According to an embodiment of the invention, a pivoting hitch for an elevator rope includes a shaft being shaped as a right cylindrical prism, with a base having a circular arc joined at both ends by a straight line whereby the shaft has a flat portion and a rounded circular portion; at least two holes through the shaft, the at least two holes being substantially perpendicular to the flat portion; the rounded circular portion of the shaft resting on a seat, wherein a shape of the seat that makes contact with the shaft is congruent to the rounded circular portion of the shaft; the seat resting on a lower hitch plate; the lower hitch plate having at least two holes therein; at least two rods each passing through a separate one of the at least two holes in the lower hitch plate, through a separate one of the at least two holes of the shaft, and through one spring each; and an end of each rod being connected to a separate termination for a rope, and another end of each rod being connected to the corresponding spring. 
     According to an embodiment of the invention, a pivoting hitch for an elevator rope includes a shaft being shaped as a right cylindrical prism, with a base having a circular arc joined at both ends by a straight line whereby the shaft has a flat portion and a rounded circular portion; at least one hole through the shaft, the at least one hole being substantially perpendicular to the flat portion; the rounded circular portion of the shaft resting on a seat, wherein a shape of the seat that makes contact with the shaft is congruent to the rounded circular portion of the shaft; the seat resting on a lower hitch plate; the lower hitch plate having at least one hole therein; at least one rod passing through the at least one hole in the lower hitch plate, through the at least one hole of the shaft, and through at least one spring; an end of the at least one rod being connected to a termination for a rope, and another end of the at least one rod being connected to the spring; and one side of the seat being contained by a hitch weldment and another side of the seat being contained by a side plate; wherein one side of the seat is contained by a hitch weldment and another side of the seat is contained by a side plate; and wherein the elevator rope is reeved from the pivoting hitch over a first sheave, a second sheave, and a drive sheave, and the first and second sheaves are attached to an elevator car that travels through a hoistway; wherein a first portion of the rope is between the pivoting hitch and the first sheave, a second portion of the rope is between the first sheave and the second sheave, a third portion of the rope is between the second sheave and the drive sheave, and a first rope angle between the first and second portions is equal to a second rope angle between the second and third portions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a typical hitch (termination) according to the prior art. 
     FIG. 2 shows an elevator car supported in an overslung fashion with a pivoting termination according to an embodiment of the invention. 
     FIG. 3 shows the pivoting termination of FIG.  2 . 
     FIG. 4 shows a horizontal shaft used in an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a wire rope  2  is connected to a thimble rod  4  which in turn is connected to a hitch plate  6 . Thimble rod  4  is secured in place with a plurality of nuts  10  and a cotter pin  8 . A centering washer  12  is sometimes used to keep thimble rod  4  aligned in hitch plate  6 . A spring  14  is optionally used to ensure that the tension on all ropes remains equal. The word “rope” means a wire rope or a coated steel belt (CSB) as those terms are used in the elevator industry as well as a synthetic non-metallic rope such as is disclosed in U.S. Pat. No. 5,881,843 (SYNTHETIC NON-METALLIC ROPE FOR AN ELEVATOR). 
     Referring to FIG. 2, a rope  20  is shown running from a pivoting hitch  40  to a first car sheave  22 , then across a top of an elevator car (not shown) to a second car sheave  24 , after which rope  20  runs to a drive sheave  26  and then to a counterweight (not shown). A rope portion  20   a  makes a rope angle α with a rope portion  20   c , and a rope portion  20   b  makes a rope angle β with rope portion  20   c . As the elevator car moves downward within a hoistway, rope angles α and β decrease, approaching a theoretical limit of 90° for an infinitely long hoistway. As the elevator car moves upward, rope angles α and β increase, and are at their maximum when the car is as high as it will go. In order to keep the elevator car horizontally centered, rope portion  20   c  must be kept horizontal, which means that rope angles α and β must be kept equal. 
     Pivoting hitch  40  includes a rod  42  which is shown here connected to rope  20 , depicted here as coated steel belt (CSB), by a CSB termination  44 . The lower end of rod  42  and CSB termination  44  are inside a car dead end hitch weldment  46 . 
     Referring to FIG. 3, rod  42  of pivoting hitch  40  runs from CSB termination  44 , through a hole  48  in a hitch plate  50 , and extending through a hole  51  in a shaft  52  where it is connected to the top of a spring  54 . Shaft  52  is optionally a ball when a single rope is being terminated, but a shaft is used when a plurality of parallel ropes are being terminated. FIG. 4 shows a shaft  52  with a plurality of holes  51  for terminating three ropes. 
     A flat top  55  of shaft  52  receives spring  54 . Spring  54  acts to maintain a stable tension on rope  20 , which helps cushion the elevator car and its occupants. Shaft  52  is seated in a seat  53  which is preferably of a material such as Dupont&#39;s Delrin®, which is a very durable acetal engineering plastic with natural lubricity. The part of seat  53  which makes contact with shaft  52  is preferably contoured to match the corresponding contours of shaft  52  which make contact with seat  53 . A plate  56  on one side of seat  53  is preferably included to contain seat  53 , whereas another side of seat  53  is preferably contained by hitch weldment  46 . 
     While the present invention has been described with reference to a particular preferred embodiment and the accompanying drawings, it will be understood by those skilled in the art that the invention is not limited to the preferred embodiment and that various modifications and the like could be made thereto without departing from the scope of the invention as defined in the following claims.