The present invention relates to a belt-shaped elevator rope used in an elevator to suspend a car.
Various layouts for an elevator system in which a car and a counterweight are suspended by a belt-shaped rope are disclosed in Japanese Patent Publication No.
The present invention aims to solve the above problems and an object of the present invention is to provide an elevator rope capable of ensuring stable strength and enabling extension of service life.
In order to achieve the above object, according to one aspect of the present invention, there is provided an elevator rope for suspending an elevator car, comprising a belt-shaped rope main body, wherein: the rope main body has a plurality of strands in which a plurality of wires are laid parallel; and a coating body made of a resin for covering and integrating the strands; and the strands are disposed side by side in a cross section perpendicular to a longitudinal direction of the rope main body.
According to another aspect of the present invention, there is provided an elevator rope for suspending an elevator car, comprising a belt-shaped rope main body, wherein: the rope main body has: a plurality of strand assemblies including a core member made of a resin extending in a longitudinal direction of the rope main body, and a plurality of strands disposed around the core member and laid together with the core member; and a coating body made of a resin for covering and integrating the strand assemblies; the strands include a plurality of wires laid parallel to each other; and the strand assemblies are disposed side by side in a cross section perpendicular to a longitudinal direction of the rope main body.
Preferred embodiments of the present invention will now be explained with reference to the drawings.
It is preferable for a diameter of the wires 4 to be made approximately 1/400 of a diameter of a sheave (not shown) around which the rope main body 1 is wound. In this manner, bending stresses generated by the sheave are reduced, enabling fatigue resistance to be improved. Furthermore, in order to avoid making the diameter of the wires 4 considerably slenderer, it is preferable for the cross-sectional construction of the strands 2 to be a Warrington type rather than a Seale type or a filler wire type as defined in JIS G 3525.
The coating body 3 is composed of a thermoplastic ether-based polyurethane resin, for example. An adhesive 5 is applied to at least an outer peripheral portion of each of the strands 2 to integrate the strands 2 with the coating body 3. That is, the strands 2 and the coating body 3 are bonded to each other by means of the adhesive 5. Timing of the application of the adhesive 5 may be either before or after the laying together of the wires 4.
In an elevator rope of this kind, because the strands 2 are disposed side by side and are covered by the coating body 3 made of a resin, movement of the strands 2 can be prevented and the occurrence of friction between the strands 2 can be prevented, thereby enabling stable strength to be ensured and also enabling extension of service life.
Because the wires 4 constituting each of the strands 2 are laid parallel to each other, the wires 4 are in line contact with each other and restrain each other. Consequently, contact pressure among the wires 4 is reduced, making internal friction less likely to occur in the strands 2, thereby also enabling stable strength to be ensured and also enabling extension of service life.
Particularly in Embodiment 1, because all of the wires 4 in all of the strands 2 are laid parallel, uniform strength can be ensured across the entire cross section, also making it superior in shape stability.
In addition, because steel wires 4 and a coating body 3 made of a hard polyurethane resin are used and the strands 2 and the coating body 3 are bonded to each other by means of the adhesive 5, ample abrasion resistance can be ensured and stability of the belt shape and cohesion of the strands 2 can be improved.
Now, if the overall strength of the rope main body 1 decreases and damage progresses, the strands 2 will break in descending order of magnitude of load burden, or in descending order of severity of damage. In regard to this, even if the number of strands 2 is increased as a preventive measure, a strength increase proportional to the number of strands 2 cannot be expected since it is difficult to make the load burden on each of the strands 2 uniform.
Furthermore, in an elevator rope integrated by a coating body 3, it is difficult to detect to what extent a given wire 4 inside the coating body 3 is damaged. In other words, it is conceivable that the replacement period for the rope main body 1 cannot be determined until damage sufficient to deform an external surface of the coating body 3 occurs in the strands 2, or at least one of the strands 2 is broken completely.
In regard to this, it is necessary to use five or more strands 2 in order to ensure a residual strength of approximately 80 percent (80%) in the rope main body 1 at the point in time when it is to be replaced due to the expiration of its service life. However, if strength has degraded to the extent that one of the strands 2 breaks, it can be surmised that damage to the other strands 2 will also have progressed and their strength degraded. Normally, the residual strength at the point in time when JIS replacement criteria are reached is in the order of a 5 percent (5%) reduction from a standard value since a safety margin from a standard breaking load is provided.
A preferred number of strands 2 can be found from the above. Specifically, if we let a be a predetermined residual strength, b be the normal residual strength under the replacement criteria, N be the number of strands 2, and P be the breaking load of the strands 2, then an expression a x P x N = b x P (N -1) is satisfied. If we assume that a is 80 percent (80%), and b is 95 percent (95%), then 0.8 x P x N = 0.95P(N - 1), and N is found to be 6.3, that is, approximately seven (7). Consequently, sufficient residual strength can be ensured if at least seven strands 2 are used.
Moreover, the material of the coating body 3 is not limited to a thermoplastic ether-based polyurethane resin, and appropriate selection in response to service conditions is possible. However, if used in a high-temperature, high-humidity environment, a hard ether-based polyurethane, in which hydrolysis is less likely to occur, is preferable to an ester-based polyurethane, in which hydrolysis occurs easily.
Next,
Each of the strand assemblies 12 respectively includes: a core member 14 made of a resin extending in a longitudinal direction of the rope main body 11; and three strands 15 disposed around the core member 14 and laid together with the core member 14. Each of the strands 15 has a plurality of steel wires 16. The wires 16 are laid parallel to each other. All of the wires 16 are laid parallel in all of the strands 15.
In each of the strand assemblies 12, the three strands 15 are disposed in a triangular cross-sectional shape around the core member 14. The strand assemblies 12 are disposed such that the disposed cross-sectional shapes of the strands 15 are alternately reversed in direction.
A thermoplastic resin such as a polypropylene resin, a polyethylene resin, or a vinyl, etc., or synthetic resin fibers such as high-strength aramid fibers or polypropylene fibers, etc., laid together at a high density, for example, can be used for the material of the core member 14.
An adhesive 5 is applied to at least an outer peripheral portion of each of the strands 15 to integrate them with the coating body 13. That is, the strands 15 and the coating body 13 are bonded to each other by means of the adhesive 5.
In an elevator rope of this kind, because the strand assemblies 12 are disposed side by side and are covered by the coating body 13 made of a resin, movement of the strand assemblies 12 can be prevented and the occurrence of friction between the strand assemblies 12 can be prevented, thereby enabling stable strength to be ensured and also enabling extension of service life.
Because the wires 16 constituting each of the strands 15 are laid parallel to each other, internal friction is less likely to occur in the strands 15, thereby also enabling stable strength to be ensured and also enabling extension of service life.
In addition, because the strand assemblies 12 are constituted by a core member 14 and three strands 15, slenderer wires 16 can be used, enabling reductions in a diameter of a sheave to which the present invention is applied.
Furthermore, because three strands 15 are disposed in a triangular cross-sectional shape around the core member 14, and the strand assemblies 12 are disposed such that the disposed cross-sectional shapes of the strands 15 are alternately reversed in direction, the strand assemblies 12 can be disposed at a high density, enabling strength to be increased while keeping the width of the rope main body 11 small, thereby enabling reductions in a width of a sheave to which the present invention is applied.
Next,
In an elevator rope of this kind, since the cross-sectional construction of the strands 18 is simple and stable, it is superior in the shape stability relative to external forces. Furthermore, a diameter of the outer peripheral wires 17 can be made comparatively large, enabling both flexibility and abrasion resistance to be ensured in a well-balanced manner. In addition, because only a single layer of the outer peripheral wires 17 is disposed around the core wire 16, movement among the outer peripheral wires 17 can be suppressed, enabling adhesion stability relative to the coating body 13 also to be improved. Thus, the service life of the outer peripheral wires 17 can be extended and fatigue resistance of portions bonded to the coating body 13 can be improved.
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