Abstract:
A termination device for terminating a flexible flat tension member includes a socket and two opposing wedges mounted therein. One of the wedges is preferably pinned within the socket while the other wedge is removable. The invention provides a reliable termination with a safety back-up to retain the tension member even if friction in the device is reduced due to soiling with a friction reducing material.

Description:
This application is a divisional of U.S. patent application Ser. No. 09/476,964, entitled “Flexible Flat Tension Member Termination Device” filed Jan. 11, 2000. 
    
    
     TECHNICAL FIELD 
     The present invention relates to elevator systems. More particularly the invention relates to a termination for a flexible flat tension member. 
     BACKGROUND OF THE INVENTION 
     A conventional traction elevator system includes a car, a counterweight, two or more ropes (tension members) interconnecting the car and counterweights; terminations for each end of the ropes at the connection points with the car and counterweights, a traction sheave to move the ropes and a machine to rotate the traction sheave. The ropes have traditionally been formed of laid or twisted steel wire which are easily and reliably terminated by means such as compression terminations and potted terminations. 
     Compression type terminations for steel ropes of larger diameters (conventional steel elevator ropes) are extremely effective and reliable. The range of pressures placed on such terminations is reasonably broad without adverse consequence. Providing that the pressure applied is somewhere reasonably above the threshold pressure for retaining the ropes, the termination is effective. 
     With an industry trend toward flat ropes, those ropes having small cross-section cords and polymeric jackets, significantly more criticality is involved in effectively terminating the same. More specifically, the polymeric coating can creep to even 50% of its original thickness when subjected to pressure. Prior art knowledge which teaches one to exceed a threshold omits a critical parameter for a flexible flat tension member. Upper limits on compression are also important for such tension members. 
     Since current knowledge in the art of tension member terminations is less than sublime for flexible flat tension members due both to the small cord diameter and the jacket properties discussed above, the art is in need of a tension member terminating device which specifically optimizes terminations of the flexible flat tension members currently emerging in the field. 
     SUMMARY OF THE INVENTION 
     A flexible flat rope (tension member) termination device is disclosed herein which comprises a socket, the socket including a pair of pins, a load side bearing wall having a friction surface, and a cut side bearing wall having a friction surface. The socket defines an interior hollow sized to accept two wedges in an opposed position relative to one another which together provide compressive and frictional forces that are desirable for securing a flat rope therein, the flat rope is threaded from a load end of the termination device around a first wedge, then back downwardly around a second wedge and then upwardly to its end. The arrangement provides about 35 MPa of compressive force on the flat rope over an effective friction surface of about 75 square centimeters. No fasteners are necessary during site assembly thus speeding assembly time and reducing cost considerations while optimizing termination reliability. In order to increase the coefficient of friction of the device, the surfaces upon which the flat rope will make contact are preferably textured. By increasing friction through textured surfaces the compressive force necessary to secure the flat rope is lower. This is desirable to reduce creep and thus extend the useful service life of the flat rope. 
     In addition to the foregoing, the reduction in creep allows for monitoring of the condition of the flat rope using magnetic flux leakage or electrical conductivity. Since creep is effectively eliminated, grounding of the rope does not occur. Thus magnetic or electrical conductivity may be monitored from one end of the rope to the other end of the rope. Since losses due to grounding are eliminated in the above discussed termination, conductive readings of the strands of the rope will accurately reflect the condition of the strands. 
     In another embodiment of the invention, a pair of capstans are employed to provide the necessary frictionally compressional forces required to terminate a flexible flat rope. One capstan is fixed while a second capstan is moveable toward or away from the first capstan. The device may be used to terminate a tension member whose working end extends downwardly from the device or whose working end extends upwardly from the device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several Figures 
     FIG. 1 is a perspective view of an elevator system; 
     FIG. 2 is a perspective assembly view of the termination device of the invention; 
     FIG. 3 is a perspective exploded view of the of the termination device of the invention; 
     FIG. 4 is a cross-sectional view of the termination device of the invention taken along section line  4 — 4  in FIG. 2; and 
     FIG. 5 is a side elevation view of a second embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, the relative location of the tension member termination device of the invention can be ascertained. For clarity, an elevator system  12  is illustrated having a car  14 , a counterweight  16 , a traction drive  18  and a machine  20 . The traction drive  18  includes a tension member  22  interconnecting car  14  and counterweight  16  which member is driven by a sleeve  24 . Both ends of tension member  22 , i.e., a car end  26  and a counterweight end  28  must be terminated. It is either of these termination points for a flexible flat tension member with which the invention is concerned. An exemplary tension member of the type contemplated in this application is discussed in further detail in U.S. Ser. No. 09/031,108 filed Feb. 26, 1998 entitled Tension Member For An Elevator and U.S. Ser. No. 09/218,990 entitled Tension Member For An Elevator filed Dec. 22, 1998, both of which are entirely incorporated herein by reference. The elevator system depicted, is provided for exemplary purposes to illustrate the location of the device of the invention. 
     Referring now to FIG. 2 a termination device  30  of the invention is illustrated. For point of reference, one of skill in the art will recognize tension member  22  which is visible at the bottom of the drawing figure and at the top of the drawing figure. The member is numbered at both places where it is visible for clarity. Tension member  22  is threaded through termination device  30  as will be discussed hereunder. 
     Termination device  30  comprises a socket  32  of a generally tubular shape which provides sides  34  and  36 , a cut side plate  38 , and a load side plate  42 . Cut side plate  38  and load side plate  42  provide friction surfaces ( 40  at cut side plate  38  and not shown at load side plate  42 ). In a preferred construction of socket  32  of the invention, side  36 , cut side plate  38  and load side plate  42  are manufactured as a unit to which side  34  is connectable by a pair of clevis pins  50  and  54 . Preferably pins  50  and  54  each employ a cotter pin (not shown) to complete the assembly. One of ordinary skill in the art will recognize cotter pin holes  60  in pins  50  and  54 . Socket  32  is thus held together between the heads of clevis pins  50  and  54  and the respective cotter pins. 
     Device  30  is supported by a support  44  having at an uphole end thereof a connector such as a pin hole  46  as shown. At a lower end of support  44  is a connector  48  which preferably is a sleeve as shown through which pin  50  is passable, said pin  50  being anchorable to socket  32  as illustrated. Any means of anchoring pin  50  to housing  32  is employable. It should be noted that the positioning of the pin  50  is selected to center the pin and thus the support  44  over the load side  52  of tension member  22  as is visible in FIG.  4 . By centering pin  50  with load side  52  of tension member  22 , device  30  is caused to hang straight and additional forces are not placed upon tension member  22 . 
     The second pin  54  is provided to positionally secure a wedge through hole  55  and prevent one of the preferably two wedges employed herein from becoming unintentionally disassociated with socket  32 . Hole  55  is preferably larger in diameter than pin  54  in order to allow wedge  56   b  to have play when pinned. The play is beneficial in that it facilitates self-centering of the wedge  56   b  with the balance of termination device  30 . Self centering ensures a very effective termination while reducing the cost of manufacturing since tolerances of manufacture are not required to be as tight due to this self-centering feature. 
     Referring to FIG. 4, a wedge system of the invention employs preferably two wedges that are identical to one another (ease of manufacturing). Each wedge  56  is tear drop shaped in cross section and provides a contact surface for the tension member  22 . Each angular surface of each wedge is preferably at about 15° from a centerline of each respective wedge. The curved portion of each wedge is preferably of a radius of 15 millimeters. The positioning of the two wedges in one preferred embodiment is well illustrated in FIG.  4 . It will be appreciated that the load side plate  42  and cut side plate  38  are parallel to one another and that the function of the wedges is to urge tension member  22  against friction surfaces on plates  38  and  42 . 
     In order to terminate tension member  22 , one need merely thread the member  22  through the device  30  from the bottom (in the drawing) and around the wedges  56  as shown. Preferably at least about 200 millimeters of tension member  22  should extend out of the device  30  and beyond cut side plate  38 . Once the wedges are “set” the termination is complete and will reliably and safely hold the elevator car. 
     It will be recognized by one of ordinary skill in the art that a single wedge  56   a  would be sufficient to reliably hold the elevator car as such single wedge systems currently are in existence. Single wedge systems typically employ friction surfaces for contact with a tension member which have a coefficient of friction of about 0.25. This coefficient of friction is easy to obtain by providing a textured surface and when provided in connection with the above-identified device allows for the termination to actually use only one of the two wedges. On occasion differing coefficients may be desired or may be imposed upon the system. In such low coefficient of friction situations a conventional single wedge termination might not be as desirable or desired. The invention, because of its greater surface area and opposed wedges  56   a  and  56   b  allows for the use of lower coefficient of friction surfaces, while still providing a reliable termination. Under normal circumstances all of the force of tension member  22  is reacted out by the time tension member  22  has wrapped completely around wedge  56   a . In other words, there is no tension left in tension member  22  after the contact areas of wedge  56   a . For this reason, wedge  56   b  plays a role only as a stop for wedge  56   a . Alternatively, the invention provides a safety backup to ensure the tension member does not slip in conditions where the coefficient of friction has degraded to less than 0.25. This can occur if the friction surfaces of plates  38  and  42  become lubricated by any number of possible lubricants. In such event, tension still remaining in the tension member beyond the contact areas of wedge  56   a  because of the reduced friction is reacted out in wedge  56   b  and the socket remains serviceable. 
     In addition to ensuring a reliable termination, the invention also ensures that creep of the polymeric jacket material is not experienced. This is beneficial since it prevents grounding of the steel cords inside the polymeric jacket against the termination device  30 . Therefore it is possible to monitor continuity, either electrically or magnetically, along the individual cords. If continuity is lost or degraded, cord damage would be suspected and repaired or the tension member replaced. 
     Referring now to FIG. 5, a second embodiment of the invention is illustrated wherein a tension member is terminated by a device having the capability of being utilized as a termination device for a tension member having a working end extending upwardly or a termination device for a tension member having a working end extending downwardly. The device includes a frame  70  which is attachable either to the top of the hoistway (not shown) or to an elevator car (not shown) or counterweight (not shown). Fixedly attached to frame  70  is bracket  72  which preferably comprises two plate like members each attached to the frame only or attached to one another via, for example, forging, etc. At one end of bracket  72 , a capstan  74  is fixedly attached thereto at a predetermined angle by any suitable mechanical affixation means. The desired angle will preferably include a positioning of one flat surface  76  of capstan  74  in a vertical position. A second capstan  78  is positioned adjacent first capstan  74  as illustrated but is not affixed to bracket  72 . Rather second capstan  78  is allowed to slide within bracket  72  in groove  80  via a pin  82  extending from capstan  78 . Groove  80  and the sliding of capstan  72  allows for simple insertion of a tension member  22  to terminate the same. The sliding provision of second capstan  78  also allows the weight of whatever object is suspended by tension member  22  to cause capstan  78  to move toward capstan  74 . This is important with respect to the termination capability of the device of the invention since the tension member  22  being wrapped as shown in FIG. 5 is compressed in the area illustrated by arrow  84  between the two capstans. 
     It should be noted that the second capstan  78  will tend to find its own position within bracket  72  since it includes a complementary angle to that of capstan  74 . Thus, it can be expected that surface  86  of capstan  78  will orient itself in a vertical position parallel to surface  76  of capstan  74 . Tension member  22  is preferably wrapped over the curved section  88  of capstan  78  through the central area  84  between capstan  74  and capstan  78 , around the curved section  90  of capstan  74  and up to an end termination on the flat surface  76  of capstan  74 . 
     The tension member  22  is preferably bolted to capstan  74  by a plurality of threaded fasteners (bolts)  92 , which preferably is six bolts. A plate  94  is used as a bolt seat and to compress tension member  22  against surface  76  of capstan  74 . In a preferred embodiment, the plate  94  includes curved ends  96  to prevent injury to tension member  22 . 
     In one preferred embodiment it is noted that a backup retaining device comprises a wedge  98  adhesively mounted to a terminal end  100  of tension member  22 . Thus, in the extraordinarily unlikely event that the tension member began to slip through the termination device of this embodiment, the wedge  98  would be drawn into the confined space between bolt plate  94  and flat surface  76  of capstan  74  where it would wedge against tension member  22  and prevent further migration of the tension member  22  out of the termination device of this embodiment. 
     Although the invention has been shown and described with respect to exemplary embodiments thereof; it should be understood by those skilled in the art that various changes, omissions, and additions may be made thereto, without departing from the spirit and scope of the invention.