Traction enhanced controlled pressure flexible flat tension member termination device

Information

  • Patent Grant
  • 6820726
  • Patent Number
    6,820,726
  • Date Filed
    Tuesday, December 22, 1998
    25 years ago
  • Date Issued
    Tuesday, November 23, 2004
    19 years ago
Abstract
A tension member termination device optimized for terminating flexible flat tension members, the device including a socket with a compression portion and a bulbous portion and a compression plate on each side of the compression plate on each side of the compression portion fastenable by fasteners extending through all of these feature. The device provides a pathway for the tension member through the device and upon torquing the fasteners reliably secures the tension member while avoiding deleterious pressure and stress therein.
Description




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 is not all that is of concern for flexible flat tension members. Upper limits on compression are also important.




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.




DISCLOSURE OF THE INVENTION




According to the present invention, a compression termination device having a friction enhancing construction while reducing compressive forces applied to the tension member, comprises a load side plate, a cut side plate and a socket, a portion of which being receivable between said load side and cut side plates and a portion of which is bulb shaped. The plates and socket are of sufficient width to accept a flexible flat tension member of a selected width and are securable together by fasteners. In a condition where the fasteners are loose, the tension member is insertable between the load side plate and socket, toward and around the bulb and back up between the cut side plate and socket whereafter tightening of the fasteners produces significant frictional forces on the tension member to retain the same while compressive forces on the tension member are intentionally limited to about 2 Mpa on the load side of the device and 5 Mpa on the cut side of the device. Friction is increased by texturing the surfaces of the termination device with which the tension member makes contact. With compressive forces as stated, creep is minimized while the termination maintains a sufficient gripping force to provide a factor of safety (fos) of 12 to maintain adequate strength of the termination.




Since creep is a possibility even with Mpa levels at the stated limits, the invention optionally includes a structure providing resilience such that compressive force on the tension member will remain in the acceptable range even if creep does occur.




The termination of the invention further optionally includes a jamming device attachable to the cut end of the tension member. In the unlikely event of tension member slippage through the termination device, the jamming device will be drawn into the termination device and will prevent the tension member cut end from pulling through the termination device.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a perspective view of an elevator system;





FIG. 2

is an exploded perspective view of the termination device of the invention;





FIG. 3

is an end elevation view of a socket of the invention;





FIG. 4

is a side elevation view of a socket of the invention;





FIG. 5

is a top plan elevation view of a socket of the invention;





FIG. 6

is a view similar to

FIG. 3

but having studs installed therein;





FIG. 7

is an end elevation view of a compression plate of the invention;





FIG. 8

is a side elevation view of a compression plate of the invention;





FIG. 9

is an end elevation view of the invention in an assembled and torqued condition;





FIG. 10

is a side elevation view of the invention in an assembled and torqued condition;





FIG. 11

is a schematic view of a nut and bolt width belleville washers thereon in the uncompressed condition;





FIG. 12

is a schematic view of a nut and bolt width belleville washers thereon in the compressed condition;





FIG. 13

is a schematic view of an alternate biasing means of the invention;





FIG. 14

is a schematic view of the termination device of the invention illustrating force directions for calculations provided herein;





FIG. 15

is a perspective view of the pivot connector of the termination device of the invention;





FIG. 16

is a perspective assembled view of the jamming device of the invention;





FIG. 17

is a perspective view of the interior portion of one side of the jamming device; and





FIG. 18

is a perspective view of the interior portion of a second side of the jamming device.











BEST MODE FOR CARRYING OUT THE INVENTION




Referring to

FIG. 1

, the relative location of the tension member termination device of the invention can be ascertained. For clarity, the elevator system


12


is illustrated having car


14


, 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 sleeve


24


. Both ends of tension member


22


i.e., car end


26


and counterweight end


28


must be terminated. It is this termination point 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 Continuation-In-Part Application 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.




Focusing on the termination device, referring to

FIG. 2

, and noting that both ends


26


and


28


may be similarly terminated, the device of the invention comprises, principally, a socket


30


around which a flat flexible tension member extends (not shown), a load side plate


80


and a cut side plate


96


. The invention further comprises a resilient compression subsystem and a pivoted connector which will be discussed hereinbelow.




Returning to the principal portion of the invention and directing attention to

FIGS. 2-5

, socket


30


includes a tapered end


32


to both ease insertion of a tension member in the loosely assembled condition of the device and additionally and importantly to avoid a sharp edge which would otherwise promote fatigue in the tension member where the member enters the termination device


10


. The taper is from both major surfaces of socket


30


i.e., load surface


34


and cut surface


36


. Socket


30


further includes troughs


38


and


40


, respectively. Troughs


38


and


40


are sized to receive a tension member of a width that has been pre-selected. Each trough nests with a section of the tension member when the termination device is assembled. Each trough may be left smooth and the termination device will remain effective. It is preferred, however, to texture each trough and the bulb surface


42


thereby increasing the coefficient of friction of all surfaces of socket


30


with which the terminated tension member will make contact. A preferred method for texturing troughs


38


and


40


as well as surface


42


is by sand blasting. It will be understood however that other methods such as machining, chemical etching, etc. could also be used.




Socket


30


further includes binding wings


44


and


46


having a plurality of fastener clearance holes


48


and, in a preferred arrangement, a plurality of stud receiving openings


50


. The number of holes


48


depends upon the length socket


30


and the allowable pressure on the tension member. In the embodiment of

FIGS. 3 and 4

, four holes


48


, and three openings


50


are provided on each wing


44


and


46


. In a preferred embodiment, openings


50


are threaded to receive studs


52


(FIG.


6


). It should be noted that studs


52


, as shown in

FIG. 6

extend only toward the cut side


36


of socket


30


. Studs


52


enable the application of a greater compressive load on cut side


36


of socket


30


than the load applied on load side


34


of socket


30


which is applied by bolts extending completely through device


10


. In other words, the load placed on the respective sides of socket


30


(through plates discussed hereunder) by the bolts (which extend through the device) and nuts is approximately equal; studs


52


allow more load to be placed on the cut side as is desirable and explained further hereinafter.




In a preferred embodiment, socket


30


(the section bound between the plates) is about 9 to about 12 millimeters thick to support the stress placed thereon.




Referring back to

FIG. 5

, surface


42


is illustrated as a depressed area between shoulders


54


and


56


. The shoulders are preferably provided to assist in properly seating a tension member when the termination is being constructed. This helps to ensure that the load bearing cords of the tension member do not experience significantly unequal leading. Significant shoulder height is not necessary to achieve the desired result. A height of about 1 millimeter for each shoulder has been found to function adequately.




The final feature of socket


30


is pin receptacle


58


which preferably includes bushing


60


therein. Pin receptacle


58


is located in bulb


62


of socket


30


but is offset from the center axis of bulb


62


. More specifically, and to minimize angular stress in the tension member, receptacle


58


is offset toward the load side


34


of socket


30


and is positioned to be aligned on center with a tension member assembled with said termination member. By so locating the receptacle, and thus the pivot point in the system, the load hanging therefrom is aligned with the load side of the tension member engaged with the termination device of the invention.




Socket


30


is important to the functionality of the termination device of the invention principally because it provides three distinct friction zones and a smooth bend surface for the tension member. The combination reduces the compression force required to prevent tension member slippage which is particularly helpful where flexible flat tension members having polymeric jackets are employed. Reducing the compression force that would otherwise be required, alleviates creep and reduces stress in the tension member. This is desirable since it may reduce the number of re-roping operations that would be carried out during the life of the elevator.




Thus far only the socket


30


has been described and it will be apparent to one of ordinary skill in the art that the socket alone does not retain the tension member. Reference is, therefore, made to

FIGS. 7 and 8

where the load side and cut side plates


80


and


96


, respectively, are described. It should be noted that plate


80


and plate


96


are identical in a preferred embodiment and are provided distinct numerals merely to distinguish each side of the termination device (which is side dependent) rather than to signify any distinction between the plates themselves.




Plates


80


and


96


are curved at longitudinal top


82


and bottom


84


ends thereof. The degree of the curvature is selected to, at end


82


, reduce fatigue of the tension member at the point where it enters the termination device. The curve at


82


preferably mirrors the tapered end


32


of socket


30


. Bottom end


84


is curved to match the transition from the compression portion of socket


30


to bulb


62


. In a preferred embodiment, the curves at


82


and


84


as well as those in the opposite plate


96


are identical so that plates


80


and


96


are interchangeable and orientable in either direction. This facilitates assembly of the termination device.




On the convex side


86


of each plate


80


and


96


(it should be noted that the sub numerals employed to describe features of each plate will be identical because the features are identical and no distinction as to side of the termination device is necessary), a region


88


is provided where a textured surface is desirable. The texture may be of any type that increases the coefficient of friction without being significantly deleterious to the jacket of the tension member. In one preferred embodiment sand blasting of the region is indicated. It will be understood that the region may be textured by machining, chemical etching, knurling, etc. if desired or otherwise indicated. A preferred range of friction for the device of the invention is about 0.15 to about 0.5. Region


88


is outlined in

FIG. 8

in phantom lines.




Due to the texturing processes, and especially the sand blasting process, the termination device may become more susceptible to corrosion. In order to avoid or inhibit such corrosion, it has been determined that yellow zinc plating may be advantageously used. Alternatively, stainless steel material or aluminum material may be used for the device of the invention.




Bordering Region


88


on each longitudinal side thereof are a plurality of clearance holes


90


. In a preferred embodiment, seven holes


90


are provided on each side of Region


88


. Holes


90


accept through passage of bolts to assemble device


10


and also studs


52


discussed with reference to FIG.


6


. Although it has been stated that plates


80


and


96


are preferably interchangeable, it is possible to eliminate holes on the load side plate


80


which correspond to studs


52


estimating only from the cut side


36


of socket


30


. The holes that can be eliminated may be ascertained by reference to

FIG. 9

wherein bolts


100


are illustrated as extending through the entire assembly and studs


52


only extend through one side thereof, therefore only requiring clearance holes


90


in the cut side plate.




Referring to

FIGS. 9 and 10

, the device


10


is illustrated in the assembled condition with bolts


100


and studs


52


properly torqued. The torque applied is discussed further hereunder but is dictated by the allowed pressure on the tension member which is about 2 Mpa on the load side and about 5 Mpa on the cut side of the termination device


10


.




Preferably a biasing arrangement is included in the assembly of device


10


, more specifically, it is desirable to anticipate possible creep of the tension member and therefore provide means to maintain the prescribed normal force on the tension member even if it is reduced in thickness by the effects of creep. One such arrangement is illustrated in

FIGS. 11 and 12

. In

FIG. 11

, the biasing arrangement of a stack of belleville washers


102


is illustrated the uncompressed state.

FIG. 12

on the other hand, illustrates the same stack of washers


102


after torquing of the bolt


100


. In the event the volume of material bound between a bolt head


194


and nut


106


(

FIG. 9

) decreases after torquing, due to creep of the tension member, washers


102


will expand and maintain the pressure on the tension member. The normal pressure on the tension member will thus be maintained. The additional benefit of easy visual inspection for creep is realized by the invention since if the washers exhibit a spaced appearance like that of

FIG. 11

, retorquing is required. Belleville washers are known to the art and do not require specific explanation. Other biasing means are also employable with the device of the invention with the joining concept being that the predetermined normal force on the tension member be maintained. One alternate biasing means is a corrugated spring metal sheet


110


which would be placed atop cut side plate


96


in place of washers


102


. Sheet


110


has holes


112


for through passage of bolts


100


or studs


52


depending upon location. Holes


112


are preferably slotted to allow for longitudinal expansion of the spring sheet during torquing of fasteners and consequent compression of spring sheet


110


.




Referring now to

FIG. 14

, a schematic view of the invention with the plates exploded from the socket and with the forces and tensions required indicated. The invention provides five friction areas which combine to form three friction zones. The areas include: (1) the inside surface of the load side plate which contacts one side of the tension member; (2) the load side of the socket (corresponds to load plate) providing friction on an opposite side of the tension member from the load side plate; (3) the bulbous section which provides a continuous frictional surface on which the tension member is on contact; (4) the cut side of the socket and (5) the cut side plate inside surface, surfaces


4


and


5


being opposed. These five areas create three friction zones that are resolved in the following equations to determine adequacy of the assembly. Each zone is mathematically quantifiable. The sum of the three frictions must be sufficient to prevent slippage. Practically speaking, it is desirable to attain a 100% holding efficiency. In order to achieve this efficiency, the sum of the three friction zones must be equal to or exceed the breaking strength of the tension member being employed. With an assembly having a 100% holding efficiency, the tension member will break before the termination device allows the tension member to slip. In the following equations, several assumptions are made: The rope breaking strength is 30,000 Newtons; the coefficient of friction (μ) for the sand blasted surfaces that are preferred in the invention is 0.25; and the plate normal force is a function of the number of bolts employed multiplied by 1540 Newtons which is the expected force delivered by each bolt. These numbers are exemplary and clearly can be adjusted depending upon circumstances. One of ordinary skill in the art following exposure to this disclosure should be fully capable of adjusting the calculations to conform to any specific parameters given without undue experimentation.

FIG. 14

is informative and used in connection with the following formulas employed to determine gripping strength of device


10


and stress in various components.




Suppose Hitch Tension is Divided Into 3 Regions:








T




1




→T




2


  (Region 1)










T




2




−T




3


,  (Region 2)






and








T




3




−T




4


  (Region 3)






we know, T


1


=flexible flat tension member breaking strength and T


4


=O,




since if T


4


>O tension member will slip in the termination device




For example, Assume




Region 1




T


1


=30,000 N=tension member Breaking Strength




μ=0.25=coefficient of friction










N
1

=

Plate





normal





force







=

12


,


320





N






(

8





bolts
×
154





ON

)















for region 1 (referring to

FIG. 14

) F


1


=μN


1






F


1


=μ(N


1


) 2 plates




F


1


=μ0.25 (12,320) 2 plates




F


1


=6160N




and








T




2




=T




1




−F




1








so










T
2

=

(


30


,


000

-
6160

)







=

23


,


840

N














Region 2




From Traction Theory We Know:











T
2


T
3


=




μθ






or






T
3


=


T
2



μθ










T
3

=



23


,


840





e



(
.25
)




(
Π
)



=


23


,


840

2.291















T


3


=10,405 N




Region 3




From Previous Calculations,








T




3


=10,405 N






and T


4


must be =<0 (values greater than 0 indicate tension member slippage) Cut side plate has 14 fasteners×1540N (the studs


52


are available only to the cut side plate)




Assume N


2


>N


1


=21,560 N, and then calculate for slippage








T




4




=T




3




−F




2








and








F




2


=μ(N


2


) 2 plates










F




2


=0.25 (21,560) 2










F




2


=10,780 N






Criteria








IF F




2




≧T




3


,






design is adequate, tension member will not slip








F




2




>T




3


? (YES)






10,780N >10,405N, so design is adequate




PRESSURE ON URETHANE tension member:




EXAMPLE I




125 mm long




Tension member is 30 mm wide






Pressure
=


N
A

=


11000





N


30





mm





.125





mm













=2.933 MPa=425 psi




In this example the pressure is beyond that taught in the invention




EXAMPLE II




Tension member plates are 190 mm long




30 mm wide






Pressure
=


N
A

=






LOAD





SIDE






12320

N




30.190

=


2.16





MPa

=



313





psi

_







(
LOAD
)














CUT





SIDE






21560

N




30.190

=

3.78





MPa







548





psi

_







(
CUT
)












IN THIS EXAMPLE THE PRESSURE EXERTED ON THE TENSION MEMBER IS ACCEPTABLE FOR BOTH SIDES OF THE TERMINATION DEVICE. THUS, PLATES ARE LONG ENOUGH.




Bolt Torque Calculations (for First Example only):




Example I




125 mm plates with 8 bolts.




LOAD PER BOLT








N




1




=N




2


=11,000 N














LOAD





PER





BOLT

=



11


,


000

8

=

1375

N












BOLT SIZE/THREADS:




M8−8 mm course thread Pitch=1.25




PROP CLASS 8.8




BOSSARD CATALOG TABLE, PRELOAD TORQUE









PRELOAD
_




TORQUE
_











17


,


050





N




24





N


-


M




BOSSARD





CATALOG






So





for





1


,


540





N






1540

17


,


050




(
24
)


=
2.17




N


-


M










T
=

0.2





F





ι





d







=


0.2






(
1540
)






8

=

2.5





N


-


M















where Ft=1540N and d=8 mm




PLATE DIMENSIONAL CALCULATIONS













I


3
16






PLATE

=

(

1





inch





strip

)











1



(

3
16

)

3


12

=


.0005493

















                        


5.4931
×

10

-
4












Δ
=


5






wl
4



384





EI











I

1
4


=



1







(
.25
)

3


12

=
.001302











Δ
=


5






(
425
)








(
1.653
)

4



384






(

3
×

10
7


)







(
.0005493
)












1.302
×

10

-
3








in
.4


_




















Δ
=



.002507





in








if





Δ

=





Pl
3


48

EI


=


425






(
1.181
)







1.653
3



48






(

5.493
×

10

-
3



)







(

3
×

10
7


)













.002866





in






(

3
16

)


















~

=



M
C


I

Uniform






Dist
.




Load




=




[
145.159
]



.1875
2


.0005493

=

-

13.608
.0005493









24


,


774





psi






M





max







wl
2

8








425







(
1.653
)

2


8


=
145.159















UNIFORM DIST. LOAD







~

1
4


=



M
C

I

=




[

145.159
_

]





[

2.50
_

]


1.302
+

10

-
3




=

13


,


935





psi













Referring to

FIG. 15

, a clevis is illustrated. Clevis


120


is seen connected to the termination assembly in

FIG. 2

(in exploded condition). The clevis is conventional and will be easily recognized by one of skill in the art. The clevis


120


is employed to provide a pivot point near a terminal end of the loaded tension member to reduce vibratory fatigue therein. Clevis


120


is connected to socket


30


by pin


122


extending through receptacle


58


.




Referring now to

FIGS. 16-18

, an optional device


130


for use with the termination device


10


is illustrated. The purpose of device


130


is to jam with termination device


10


in the unlikely event of tension member slippage through device


10


. Device


130


is clamped onto the cut end of the tension member somewhere beyond region T


4


as discussed above. When engaged with the tension member, device


130


cannot move thereon. Thus, if the tension member slipped it would draw device


130


into contact with cut side plate


96


and side


36


of socket


30


and would jam there preventing further slippage.




Device


130


comprises a female portion


132


(

FIG. 17

) and a male portion


150


(FIG.


18


). Female portion


132


features a tension member groove


134


approximately the thickness of the tension member which is intersected by crimp grooves


136


and


138


. Bore holes


140


are provided for through passage of fasteners


142


. Male portion


150


provides tension member deformation ridges


152


and


154


which are intended to extend into grooves


136


and


138


, respectively upon assembly of device


138


. Portion


150


further includes holes


156


which are coaxially with holes


140


when device


130


is assembled to facilitate through passage of assembly bolts


142


.




In use, a cut end of a tension member, i.e., the end not being used to support the elevator, is inserted in groove


134


and portion


150


is placed in position. When the bolts


142


are tightened, ridges


152


and


154


force the tension member to follow a tortuous path around the ridges and into grooves


136


and


138


. In this way the tension member is prevented from moving relative to device


130


and if device


130


moves into contact with device


10


to tension member slippage, the slippage will be arrested.




While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of invention. Accordingly, it is to be understood that the present invention has beer described by way of illustration and not limitation.



Claims
  • 1. A tension member termination device for an elevator system comprising:a socket having a bulbous end, said socket defining a tension member path therearound; a load side plate affixable to said socket to apply a normal pressure to a load side of an end of a tension member between said socket and said load side plate; and a cut side plate affixable to said socket to apply a normal pressure to a cut side of said end of said tension member between said socket and said cut side plate; wherein said path defined by said socket includes a surface which is textured to increase the coefficient of friction thereof.
  • 2. A tension member termination device for an elevator system as claimed in claim 1 wherein said surface is sand blasted.
  • 3. A tension member termination device for an elevator system as claimed in claim 1 wherein said load side plate and said cut side plates are affixed to said socket by a plurality of fasteners common to both plates.
  • 4. A tension member termination device comprising:a compression member against which a tension member is compressible, said compression member having a load side and a cut side; a pivot associated with said compression member, said pivot having a center wherein said the center of said pivot is aligned with a tension member in the load said of said compression member.
  • 5. A tension member termination device for an elevator system comprising:a socket having a bulbous end, said socket defining a tension member path therearound; a load side plate affixable to said socket to apply a normal pressure to a load side of an end of a tension member between said socket and said load side plate; and a cut side plate affixable to said socket to apply a normal pressure to a cut side of said end of said tension member between said socket and said cut side plate; wherein said socket further includes studs extending from said socket in a direction to intersect said cut side plate enabling a greater compressive load to be placed upon said cut side plate than said load side plate.
US Referenced Citations (23)
Number Name Date Kind
216013 Ida Jun 1879 A
421120 Young Feb 1890 A
966243 Ritter Aug 1910 A
982742 Piper Jan 1911 A
1164115 Pearson Dec 1915 A
1450528 Varney Apr 1923 A
1730197 Elsey Oct 1929 A
2062653 Hocher Dec 1936 A
2189671 Mardis Feb 1940 A
2223389 Schaedler Dec 1940 A
2234029 Heckendorf Mar 1941 A
2552173 Hocher May 1951 A
3052320 Dardy Sep 1962 A
3103344 Figge Sep 1963 A
4143446 Down Mar 1979 A
4388837 Bender Jun 1983 A
4405828 Shook Sep 1983 A
4570753 Ohta et al. Feb 1986 A
5435044 Ida Jul 1995 A
5526552 De Angelis Jun 1996 A
5566786 De Angelis et al. Oct 1996 A
5855254 Blochle Jan 1999 A
6173872 Cohen Jan 2001 B1
Foreign Referenced Citations (16)
Number Date Country
679268 Feb 1964 CA
2154422 Mar 1996 CA
318110 Jan 1920 DE
1010713 Jan 1920 DE
589075 Dec 1933 DE
2136540 Dec 1933 DE
613640 May 1935 DE
115089 Sep 1975 DE
3623407 Jan 1988 DE
999585 Nov 1949 FR
754786 Aug 1956 GB
1 401 197 Jul 1975 GB
2134209 Aug 1984 GB
8-40669 Feb 1996 JP
PCTFI9700823 Jan 1997 WO
PCTFI9700824 Jan 1997 WO
Non-Patent Literature Citations (3)
Entry
PCT Search Report for Ser. No. PCT/US99/03642 dated Jun. 1, 1999.
PCT Search Report for Ser. No. PCT/US99/03642 dated Jun. 1, 1999.
Hannover Fair 1998.