Textiles: spinning – twisting – and twining – Strand structure – Covered or wrapped
Reexamination Certificate
1999-10-18
2001-11-13
Lindsey, Rodney M. (Department: 3765)
Textiles: spinning, twisting, and twining
Strand structure
Covered or wrapped
C057S213000
Reexamination Certificate
active
06314711
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a synthetic fiber rope, preferably of aromatic polyamide.
Especially in materials handling technology, for example on elevators, in crane construction, and in mining, ropes are an important element of machinery and subject to heavy use. An especially complex aspect is the loading of driven or over pulleys deflected ropes, for example, as they are used in elevator construction.
In conventional elevator installations the car sling of a car, which is moved in an elevator hoistway, and a counterweight are connected together by a steel rope. To raise and lower the car and the counterweight, the rope runs over a traction sheave that is driven by a drive motor. The drive torque is transferred by friction to the section of the rope which at any moment is lying in the angle of wrap. At this point the rope is subjected to high transverse forces. As the loaded rope is reversed by passing over the traction sheave, the strands move relative to each other to compensate for differences in tensile stress. The same refers to ropes wound on drums as they are used in elevators or cranes.
On elevator installations the lengths of rope needed are large, and considerations of energy lead to the demand for smallest possible masses. High-tensile synthetic fiber ropes, for example of aromatic polyamides or aramides with highly oriented molecule chains, fulfil these requirements better than steel ropes.
By comparison with conventional steel ropes of the same cross sectional area, ropes constructed of aramide fibers have a substantially higher lifting capacity and only between one fifth and one sixth of the specific gravity. In contrast to steel, however, the atomic structure of aramide fiber causes it to have a low ultimate elongation and a low shear strength.
Consequently, so that the aramide fibers are subjected to the smallest possible transverse stresses as they pass over the traction sheave, there is proposed in European patent document EP 0 672 781 A1, for example, an aramide fiber rope suitable for use as a traction rope. Between the outermost and inner layers of strands there is an intersheath which prevents contact between the strands of different layers and thereby reduces the wear due to their rubbing against each other. The previously known aramide rope described so far has satisfactory values of service life, resistance to abrasion, and fatigue strength under reversed bending stresses; however, it has been established that due to the parallel lay there is a possibility that in the permanently loaded traction rope, an inner torque acts over a section of rope beginning at the traction sheave, and as it passes over the traction sheave the section twists or untwists about its longitudinal axis. As a consequence of the resulting stress, changes in the structure can occur, which then lead to excessive length of individual outermost strands. The excessive lengths are transported within the rope in repeated passages of the rope over the traction sheave. Such a change in the structure of the rope is undesirable because it could lead to a reduction in the breaking load of the rope or even to failure of the rope.
SUMMARY OF THE INVENTION
An objective of the present invention is to avoid the disadvantages of the known synthetic fiber rope and to propose a synthetic fiber rope with a non-twisting structure.
The advantages resulting from the present invention relate to the fact that torques which arise under load due to the construction of the rope are by means of the opposite lay of the strands of the outer layer to the inner strands that carry them mutually canceled out resulting externally in a non-twisting rope construction. In principle, the advantages are obtained by any rope according to the invention which is under tensile loading irrespective of whether the rope in question is used in a moving or stationary manner.
It is advantageous to construct the inner layer of strands from strands with different diameters. An arrangement which alternates large-diameter strands and small-diameter strands results in a layer of strands with an almost circular cross section and a high fill factor. Overall, the strands then lie close together and support each other, resulting in a very compact and firm lay which deforms little on the traction sheave and demonstrates no tendency to unwind.
Furthermore, due to strands of different layers lying on top of and parallel to each other, contact occurs along their length which results in a much lower level of surface pressure perpendicular to the strands. This applies in the same way to aramide fibers of a strand. If the synthetic fibers of a strand are laid in the same direction of lay as the strands themselves, improved cohesion of the lay is obtained.
Moreover, the service life of parallel laid strands can be increased if, for example, in a parallel lay rope with two layers, the direction of twist of the fibers of strands of one layer of strands is opposite to the direction of twist of the fibers of strands of the other layer.
An advantageous distribution over the entire cross section of the strands of the forces acting on a synthetic fiber rope used as a traction rope is achieved in a preferred embodiment of the invention by means of the strands on the outside and the strands of the inner layer of strands being laid with a ratio between their lengths of lay of between 1:5 and 1:8. When the rope is loaded this results in a homogeneous distribution of stress over all the high tensile strands. This means that all the strands contribute to the tensile strength of the rope, thereby giving a high fatigue strength under reversed bending stresses and a long service life for the rope overall.
REFERENCES:
patent: 1373632 (1921-04-01), Phelps
patent: 3106815 (1963-10-01), Nance et al.
patent: 3395530 (1968-08-01), Campbell
patent: 3425207 (1969-02-01), Campbell
patent: 4022010 (1977-05-01), Gladenbeck et al.
patent: 4050230 (1977-09-01), Senoo et al.
patent: 4202164 (1980-05-01), Simpson
patent: 4270341 (1981-06-01), Glushko
patent: 4317000 (1982-02-01), Ferer
patent: 4365467 (1982-12-01), Pellow
patent: 4624097 (1986-11-01), Wilcox
patent: 4716989 (1988-01-01), Coleman et al.
patent: 4827708 (1989-05-01), Verreet
patent: 5526552 (1996-06-01), De Angelis
patent: 5566786 (1996-10-01), De Angelis
patent: 5852926 (1998-12-01), Breedlove
patent: 5881843 (1999-03-01), O'Donnell et al.
patent: 6068087 (2000-05-01), Moncini
patent: 925181 (1963-05-01), None
patent: 986994 (1983-01-01), None
U.S. application No. 09/422,527, filed Oct. 21, 1999.
U.S. application No. 09/449,330, filed Nov. 24, 1999.
U.S. application No. 09/449,332, filed Nov. 24, 1999.
U.S. application No. 09/487,985, filed Jan. 20, 2000.
U.S. application No. 09/488,290, filed Jan. 20, 2000.
U.S. application No. 09/488,304, filed Jan. 20, 2000.
Inventio AB
Lindsey Rodney M.
MacMillan Sobanski & Todd LLC
LandOfFree
Stranded synthetic fiber rope does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Stranded synthetic fiber rope, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stranded synthetic fiber rope will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2606155