Textiles: spinning – twisting – and twining – Strand structure – Covered or wrapped
Reexamination Certificate
2000-01-20
2001-11-27
Worrell, Danny (Department: 3741)
Textiles: spinning, twisting, and twining
Strand structure
Covered or wrapped
C057S211000, C057S232000
Reexamination Certificate
active
06321520
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates a sheathed synthetic fiber rope, preferably of aromatic polyamide, and a process for manufacturing it.
In materials handling technology, especially on elevators, in crane construction, and in open-pit mining, moving ropes are an important element of machinery and subject to heavy use. An especially complex aspect is the loading of driven ropes, for example as they are used in elevator construction and for suspended cable cars. In these instances 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.
Such a sheathed synthetic fiber rope has become known from the European Patent document 0 672 781 A1. There, the synthetic sheath is applied by extrusion in such a manner that a large surface of adhesion to the strands is formed. However, when the rope bends on the rope sheave or pulley the strands perform compensatory movements which, under certain circumstances, can cause relative movement of the strands of different layers of strands. These movements are greatest in the outermost layer of strands and particularly when the drive torque is transferred by friction to the section of rope lying in the angle of wrap of the rope sheave, can cause the sheath to lift off and form pile-ups. Such a change in the structure of the rope is undesirable because it can cause the rope to have a short service life. The same applies to ropes wound on drums as they are used in mining.
The problem underlying the invention is that of proposing a sheathed synthetic fiber rope with a long service life, as well as a method for producing such a rope.
SUMMARY OF THE INVENTION
The present invention concerns a synthetic fiber rope having a stranded core surrounded by an intersheath. A covering layer of stands is laid on the intersheath and the covering layer is surrounded by a rope sheath.
The advantages resulting from the invention consist of a lasting bonding of the sheath in the outermost layer of strands. In addition to the former adhesive bonding to as large a contact surface as possible of the outermost layer of strands, according to the invention the sheath is fastened with anchoring means which are structurally anchored in the outermost layer of strands. Especially when the join is in one piece, the bonding forces between the sheath and the anchoring means correspond to the strength of the material of the anchoring means, and are thereby many times greater than conventional adhesive forces. If the anchoring means are connected to the outermost layer of strands by positive fit, separation of the sheath is then only possible with accompanying damage to the aramide fiber strands.
As a further advantage of integrating the anchoring means into the rope structure of the outer layer of strands in combination with the single piece bonding to the sheath, for example bonding with adhesive, as the rope passes over the traction sheave the anchoring means follow the movement and/or deformation of the outermost layer of strands. By appropriate selection of a material with suitable elastic deformability, the forces acting in the layer of aramide fibers and, as a result of the bending load, in the sheath can be mutually balanced out, thereby preventing relative movement between the sheath and the layer of strands.
In a further development of the invention, the anchoring means and the sheath are made of weldable or vulcanizable materials. This choice of materials makes it possible to join the anchoring means and the sheath with no additional bonding agent. At the same time, the joint is permanent, displays material behavior identical to that of the joined parts themselves, and is therefore equivalent to a single piece construction of the anchoring means and the sheath. The joint is particularly homogeneous if the anchoring means and the sheath are made of identical material. The uniform material parameters then occurring make-it simpler to join the parts to be joined with uniform molecular bonding.
In addition to the functional advantages achieved by the invention, manufacturing sheathed synthetic fiber ropes according to the invention can be done simply, and with minimal modification to conventional rope laying machines. Over a rope core manufactured in known manner, load-bearing fiber strands with anchoring means are laid in the outermost layer of strands. The fiber strands are then thermally or chemically pre-treated before the sheath of synthetic material is applied, and the fiber strands then form a molecular bond with the means of anchoring. With conventional rope laying machines it is adequate to retrofit a pre-treatment station, apart from which there is only adjustment work to be done.
If the anchoring means and the sheath are welded to each other, essentially a heating device must be provided to heat the anchoring means so that when the sheath is extruded, permanent fusion of the sheath and the anchoring means takes place.
In a further preferred alternative process the sheath is vulcanized onto the outermost layer of strands. In this embodiment a substrate is applied to the anchoring means by use of a suitable pre-treatment station which slightly corrodes them, and in this way prepares them for molecular interlinking with the extruded sheath.
In a preferred embodiment of the invention the anchoring means take the form of one or more anchoring strands which together with load-bearing aramide fiber strands are laid into the outermost layer of strands. The twisted rope structure resulting from the helical twisting of the strands around each other already provides in a simple manner a positive fit of the anchoring strands on the outermost layer of strands. The anchoring of the sheath can be adjusted via the number of anchoring strands laid in the outer layer. A particularly good positive fit is achieved with this embodiment if the anchoring strands have a smaller diameter than the load-bearing aramide fiber strands. The circumference of each anchoring strand is squeezed between two aramide fiber strands of larger diameter, and thereby anchored in the layer of strands. Pre-manufactured anchoring strands can be processed together with the aramide fiber strands by the same rope-laying machine.
Furthermore, the anchoring means can take the form of anchoring fibers that are twisted together with aramide fibers and fixed to them to form load-bearing strands for the outermost layer of strands. The anchoring fibers are arranged in the outermost layer of fibers of the strands, and are also bonded as a single piece to the sheath, which is subsequently extruded on to them. Having a large number of such anchoring strands creates a large total bonding area between the sheath and its anchoring which strengthens the bond and also lengthens the service life of the rope.
Furthermore, the thin anchoring strands can be heated to melting temperature in a short space of time and with relatively low expenditure of energy, as a result of which this embodiment is advantageous for continuous extrusion of the sheath onto the rope.
The synthetic fiber rope according to the invention affords advantages in elevator installations, for example, where it connects the car frame of a car guided in an elevator hoistway to a counterweight. For the purpose of raising and lowering the car and counterweight, the rope passes over a traction sheave that is driven by a drive motor. As the synthetic fiber rope according to the invention passes over the traction sheave, no relative movement occurs between the rope sheath and the synthetic fiber rope.
REFERENCES:
patent: 3395530 (1968-08-01), Campbell
patent: 4022010 (1977-05-01), Gladenbeck et al.
patent: 4299884 (1981-11-01), Payen
patent: 4550559 (1985-11-01), Thomson
patent: 5526552 (1996-06-01), De Angelis
patent: 5566786 (1996-10-01), De Angelis et al.
patent: 5881843 (1999-03-01), O'Donnell et al.
patent:
Inventio AG
MacMillan Sobanski & Todd LLC
Worrell Danny
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