Abstract:
Several embodiments of terminations for flat flexible tension members include wedge type terminations, pinching terminations, and frictional terminations and combinations of the above.

Description:
TECHMICAL FIELD 
     The present invention relates to elevator systems. More particularly, the invention relates to various embodiments for terminating a flexible flat tension member. 
     BACKGROUND OF THE INVENTION 
     A conventional traction elevator system includes a car, a counterweight, two or more tension members interconnecting the car and counterweights; terminations for each end of the tension members at the connection points with the car and counterweights, a traction sheave to move the tension members and a machine to rotate the traction sheave. A second type of conventional elevator roping system is known to the art as a 2-to-1 roping system where the rope is terminated to a dead hitch and not the counterweight and car. The tension members have traditionally been formed of laid or twisted steel wire which are easily and reliably terminated by means such as a compression terminations and potted terminations. 
     Compression-type terminations for steel tension members of larger diameters (conventional steel elevator tension members) 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 tension members, the termination is effective. 
     Clamp-type and existing wedge-type and termination devices have been employed for flexible flat tension members and are adept at providing reliable terminations. They are, however, expensive and can be difficult to disassemble, after weighting. The expense related to clamp-type terminations is due to the number of individual components needed as well as the time for installing the same. Existing wedge-type terminations, while being less expensive to manufacture than clamp-type terminations and less time consuming to install, they are still more expensive than is desirable in the industry due to the need for a texturing of the surface to prevent the coefficient of friction on the wedge from dropping below the number required to prevent movement of the tension member therethrough for example if the wedge becomes unintentionally lubricated. Moreover, existing wedge-type terminations when used with flat tension members tend to be difficult to disassemble for maintenance after a load has been placed on them. Thus, the art is still in need of a termination device that reaches an advantageous price point, is easy and timely to assemble and is easy and timely to disassemble. 
     SUMMARY OF THE INVENTION 
     The above-identified drawbacks of the prior art are overcome or alleviated by the termination device of the invention. The termination device of the invention is a single wedge device wherein the wedge is maintained in position (tension wrapped therearound) by a load side of a socket on one side and on the other side by two pins, one being fixed and one being removable which pins are mounted on said socket. The device operates similarly to other single wedge termination devices in that the wedge is drawn downwardly into a socket to provide compressive force on a tension member threaded between the socket and the wedge. The device of the invention differs, however, in significant ways in that it reliably terminates a tension member while using less material and less height, pinches the flat rope in a desirable location (stronger holding capacity) and additionally facilitates easy assembly and disassembly of the device. While prior art wedge devices are easy to assemble, they are difficult to disassemble as noted above. By employing the removable pin arrangement for the device of the invention, the wedge remains easily removable without regard for creep of the tension member jacket over time. The removable pin is positioned so that when installed it provides excellent support for the wedge and when it is disengaged, allows the wedge to be easily removed from the socket. 
     In another embodiment of the invention the “pinching” effect on the tension member is provided by a protrusion or bump on the unloaded side of the termination device. The “bump” pinches the tension member providing a stronger holding capacity. Moreover, the location of the bump causes a redistribution of the normal force associated with the load side of the termination device to move compressive force to location experiencing less tensile force. 
     In another embodiment of the termination devices of the invention a lever concept is employed to terminate a tension member where no additional parts such as wedges are necessary. Rather in the lever embodiment, a tension member need merely be inserted into the device and a load placed on the tension member. The load pulls on one end of the device which imposes a compressive force on the tension member in another end of the device. The concept is applicable primarily to low overhead applications but of course could be used for any application. 
     In yet still another embodiment of the invention, a rotary termination device is disclosed which provides significant frictional surface area to remove tensile stress in a tension member and simultaneously allows a component of the device having the frictional surface area to rotate and provide a clamping or compressive force to a cut end of the tension member against a second component of the device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several FIGURES: 
     FIG. 1A is a perspective view of a one-to-one elevator system; 
     FIG. 1B is a perspective view of a two-to-one elevator system; 
     FIG. 2 is a perspective partially exploded view of a first embodiment of the invention; 
     FIG. 3 is a elevation view of the first embodiment of the invention; 
     FIG. 4 is top plan view of the same invention; 
     FIG. 5 is a partial perspective view of the first embodiment of the invention; 
     FIG. 6 is a schematic cross section of a second embodiment of the invention; 
     FIG. 7 is a schematic side elevation view of a third embodiment of the invention which employs leverage to apply a compressive force on a tension member; 
     FIG. 8 is a schematic side view of a fourth embodiment similar to the embodiment of FIG. 7 but providing further and enhanced compressive area; 
     FIG. 9 is a another schematic side view of a fifth embodiment of the invention where friction in the device prior to the leverage point is enhanced; 
     FIG. 10 is a schematic side view of an sixth embodiment of the invention; 
     FIG. 11 is an enlarged view of a portion of the embodiment of FIG. 10 found within circumscription line  11 — 11 ; and 
     FIG. 12 is a across section view of the invention of FIG. 10 taken along section line  12 — 12  in FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1A, the relative location of the tension member termination device of the invention can be ascertained. For clarity, an elevator system  12  is illustrated having 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 sheave  24 . In an alternate configuration, referring to FIG. 1B a two-to-one roping system is illustrated. The general components of such system are a car  15  and counterweight  17  which are interconnected by tension member  22  through idlers  21  and traction sheaves  19 . Such systems are generally compensated by compensation line  25  and sheave  23 . The tension member of this configuration is connected to dead end hitches at  29 . Both ends of tension member  22 , i.e., a car end  26  and a counterweight end  28  or, in a 2-to-1 roping embodiment, the two dead end hitches  29  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 also entitled Tension Member For An Elevator and 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 perspective partially exploded view of the termination device  30  is illustrated. One of ordinary skill in the art will appreciate the compact size of a socket  32  of the invention. Socket  32  provides support for preferably three pins and a wedge to terminate a tension member. At the top of the drawing, socket  32  provides a pin mount  34  to support a pin  35  and bolt  37  (FIG. 5) which conventionally attaches to a dead hitch  29  (FIG. 1B) or to the car and counterweight of FIG.  1 A. Socket  32  further provides a fixed pin mount  36  to support a fixed pin  38  (could be removable) and a removable pin mount  40  to support a removable pin  42 . The location of pins  42  and  38  relative to a wedge  44  inserted into socket  32  with a flat tension member  22 , control the distribution of the normal pressure on the tension member  22  exerted by wedge  44  against socket  32 . This is important to the invention and beneficial to the industry because the total stress in any terminated tension member is the combination of the tensile stress imposed by the load on the tension member  22  and the normal compression stress imposed by a wedge or other clamping device. The tensile stress in the member is highest where the tension member  22  enters the termination device  30 . The tensile stress in tension member  22  is lessened as it extends into the termination device because of friction between wedge  44  and socket  32  on a load side  54  (FIG. 3) of the device  30 . Thus by the time tension member  22  reaches a rounded portion  46  of wedge  44 , much of the tensile stress originally existing in tension member  22  due to a load thereon occasioned by a hanging elevator car or counter weight (not shown) has been removed by friction. By distributing the normal compressive stress away from an entrance  48  to the termination device  30 , total member stress can be reduced making re-roping operations less frequent. 
     Controlling the normal compressive stress on tension member  22  is a function of the size and angle of wedge  44  in combination with the locating pins  38  and  42 . A preferred placement according to the invention is one in which compressive stress is reduced where tensile stress is high, shifting higher a compressive force to areas where tensile stress in tension member  22  is less. More specifically, pin  38  should be located to allow wedge  44  to apply a lesser compressive load to the tension member  22  at the opening of socket  32 . Pin  42  is placed such that wedge  44  will create a greater compressive load on tension member  22  at a higher location  50  on wedge  44  than near an entrance  48  to socket  32 . Pin  38  is positioned to allow wedge  44  in the vicinity of point  52  to move slightly to the left in FIG. 3 to unload (compressive force) tension member  22  at entrance  48  to socket  32 . One of ordinary skill in the art will appreciate that the pin location and the angle of wedge  44  work together to create the distribution of compressive load. Moreover and as is visible in FIG. 3, the pattern of the tension member  22  wrapping around the various components of device  30  is also a factor in biasing compressive stress to region  50 . 
     Focusing on FIG. 3, it will be appreciated that tension member  22  enters socket  32  at entrance  48  and is frictionally and compressively secured on load side  54  of socket  32 /wedge  44 . In this location, the majority of the tensile stress existing in tension member  22  from the load of the elevator car is removed therefrom. Preferably about 50% of the tensile stress in member  22  is removed in this section (assuming a coefficient of friction of about 0.25). Tension member  22  then extends over curved section  46  of wedge  44  where more frictional forces are available but compressive forces are not. Tension member  22  loses about 60% more of the remaining tensile stress in this region. Proceeding down wedge  44  to second flat surface  56 , the balance of tensile stress is removed from tension member  22 . There is also, as will be noted from the drawing, a compressive force on the tension member in the area of flat surface  56  and an additional “pinching” force from pin  42  and from pin  38 . The pinching force additionally helps to lock tension member  22  into termination device  30 . It is important to note that the pinching profile provided must be located after the curved section  46  because in this location the tensile force in the rope has been reduced by friction and compression and allows the luxury of a high locally compressed area without risk of breakage. Tension member  22  is wrapped around pin  38  and then passed between pin  42  and wedge  44  to complete the termination. It is important to note that a single width of tension member  22  is deposed between pin  38  and wedge  44  while a double thickness of tension member  22  is disposed between pin  42  and wedge  44 . This functions to increase compressive loading of tension member  22  both between pin  42  and wedge  44  and between wedge  44  and socket  32  in region  50 . In addition, a security clamp (not shown) can be added at cut end  60  of tension member  22  but is not necessary. 
     A benefit of the arrangement of the invention is that pin  42  is specifically removable. This is important with respect to disassembly for adjustment or re-roping operations. By removing pin  42 , wedge  44  need only be lifted a small amount to relieve termination pressure on tension member  22 . Wedge  44  is then easily removed from termination device  30  and the tension member released. Because of the much reduced level of effort and time required to disassemble the device, expense is saved and the art is benefited. Moreover, the termination device  30  itself is less expensive to manufacture due to the simple components thereof. 
     In a second embodiment of the invention a socket  70  is formed to receive a wedge  72  wherein load side  74  of socket  70  is located relative to dead hitch pin hole  76  to center pin hole  76  over a load side of tension member  22  so that the load (elevator car not shown) will hang from dead hitch (not shown) through pin hole  76  in a centered manner. The device, then, creates no additional stress on tension member  22  due to bending. Tension member holding of the invention is provided by friction and compression on load side  74  of socket  70  and additionally by a pinching feature  78  located on an unloaded side  80  of socket  70 . 
     Load side  74  of socket  70  is preferably of a high coefficient of friction. Texturing to enhance the coefficient of friction on the inside surface of load side  74  for a distance which may be from a small area to an area equivalent to the length of a wedge may be done to increase the natural coefficient of friction of the material of socket  70  if required or desired. Load side  74  functions identically to the foregoing embodiment in all respects. 
     At the unloaded side  80  of socket  70 , wedge  72  bears upon only a “bump”  78  or other raised surface feature which provides a pinching effect on tension member  22  against wedge  72 . The bump itself is preferably elongated in the lateral direction so that the peak of the bump entirely traverses tension member  22 . Preferably the bump is rounded to provide better holding power on the tension member  22 . The placement of bump  78  is also important to the invention since its placement has an effect on the compressive load imposed on the load side  74  of socket  70 . By carefully placing bump  78 , the compressive load may be shifted to a location on load side  74  that is subject to less tensile stress from the load of an elevator car (not shown). The stress distribution has been discussed hereinbefore and is applicable to this embodiment identically. 
     Referring now to FIG. 7 another termination device of the invention is illustrated. This embodiment applies compressive force to the tension member  22  through a leverage arrangement. Leverage is created, by lower lever  140  through fulcrum  142  to upper lever  144 . It is to be understood the terms “lower” end and “upper” are relative and could be reversed without changing the friction of the device. 
     Lower lever  140  preferably provides a top surface  146  having a radiused load end  148  which radius is preferably selected to meet minimum bend radius requirements for a flat tension member. A pin  150  is provided for fulcrum  142 . Preferably sufficient room is provided between a pair of arms  152  extending from lever  144  to receive lever  140  and tension member  22 . Arms  152  are also preferably long enough to provide minimally enough space between surface  146  of lever  140  and a lower surface  154  of lever  144  to allow tension member  22  to be invested therebetween. It should also be noted that lever  144  is preferably longer than lever  140  in order to provide material in which pin hole  156  may be bored and be centered above a load direction of tension member  22 . 
     In another embodiment of the invention, referring to FIG. 8, the basic concept remains the same but compressive force generated by the device is enhanced due to the location of the generation of such force. The embodiment includes a lower level  162  having a friction surface  164  with a radius  166  on one edge thereof and an angled surface  168  on another edge thereof. A pivot pin  170  is located in a preselected position relative to the length of lower level  162 . The appropriate placement of pin  170  is determined by calculation and is discussed further hereunder. An upper lever  172  is preferably longer than lever  162  on one end thereof to provide material through which pin hole  174  is provided. On an opposite end of lever  172  from pin hole  174  is angled section  176  which is provided with an angled contact surface  178 . Contact surface  178  is preferably about parallel with angled surface  168  when the upper and lower levers  162 ,  172  are in a parallel relationship to one another. Arms  180  (only one visible) are preferably long enough to space lever  172  from lever  162  by an amount sufficient to ensure that compression of the rope occurs between surface  168  and  178  and not between the horizontal surfaces. 
     In the embodiment, the tension member  22  is threaded through from right to left in the drawing. The load (elevator car not shown) placed on tension member  22  causes the termination device to act by pulling the right side of lever  162  downwardly making the left side of lever  162  impinge on surface  178  of lever  172 . The clamping or compressive force on the tension member between surfaces  168  and  178  is dictated by:        FN   =     F                   R     (       S   ·   sin                   α     )                                
     Where F is the load on tension member  22 ; 
     R is the distance between a center of load F and pivot point  170 ; 
     S is the distance between pivot point  170  and the desired location of clamping force FN, as shown in FIG. 8; 
     α is the angle between a line normal to lever  172  and surface  178 . 
     Mechanical advantage is increased in this embodiment as can be illustrated by an example. Where the latter embodiment would create a mechanical advantage of 3, the angular surfaces of this embodiment where the angle a =20 degrees provide a mechanical advantage of 8.8. A significant enhancement is therefore realized in this embodiment without adding significant complexity to the device. 
     In yet another similar embodiment of the invention, referring to FIG. 9, the termination device  190  is made shorter than its two proceeding cousins by adding frictional forces through curved contact surfaces. The device does not experience higher loading on the pivot than the embodiments of FIGS. 7 and 8. In this embodiment an upper lever  192  provides a sinuous contact surface  194  on its lower surface which approximates a sinuous contact surface  196  on lower lever  198 . The sinuous surfaces provide enhanced frictional characteristics and thus remove tensile stress from tension member  22 . By so removing the leverage on a pivot pin  200  in lower lever  198  is not made higher by a shorter overall length of device  190 . A pin hole  202  is provided in upper lever  192  to secure device  190  to a dead end hitch (not shown). 
     Referring now to FIGS. 10-12 another alternative termination device of the invention is illustrated. The device  210  employs a rotary movement with a substantial friction surface  212  on a cam  214  as well as a clamping action on cut end  216  of tension member  22  between cam  214  and socket  218 . 
     Cam  214  is of a complex french curve-type configuration with a hole  222  bored therein to nest with boss  224  of socket  218 . The bored hole is preferably off center in cam  214 . The location of hole  222  is dictated by maximizing the ratio between r 1  and r 2 . Cam  214  is rotatable about boss  224  which causes cam extension  226  to come into compressive contact with knob  228  of socket  218  (an impingement area). Since cut end  216  of tension member  22  passes between cam extension  226  and knob  228 , it is subjected to compressive force when cam  214  is urged to rotate by a load being placed upon tension member  22 . 
     The force retaining tension member  22  is defined as F 2 . F 2 =K fric X Fnorm          Where                 Fnorm     =     F1   ×       (     R1   /   R2     )       Tan                 a                                
     R 1  and R 2  are distances as depicted in FIG.  10  and angle a is the angle between the knob surface and the trajectory of the motion of the cam extension  226  in the point of contact when cam is rotating about boss  224 . 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.