Wire rope having a durable marker

Described is a novel marker for wire ropes, in the form of a polymer, e.g., polyester film carrying a highly abrasion-resistant impression. This polyester film is wound around a support element in spirally overlapping manner and is worked into a gap between the bundles of strands, at the same twisting angle as the latter.

BACKGROUND OF THE INVENTION 
The present invention relates to a wire rope which comprises several 
strands twisted together around a fiber or steel rope core and which 
contains a durable marker. 
It is difficult to distinguish qualitative characteristics of wire ropes, 
such as strength, metal composition, resistance to corrosion, etc., simply 
by the outward appearance of the ropes. Therefore, attempts have been made 
to mark the individual wire ropes according to the various technical 
applications for which they are intended. However, quite a number of 
problems have come up in trying to realize this aim. 
For example, when ropes are guided over rollers, the individual strands are 
shifted relative to the core, whereby high specific pressures are 
observed. In general, the conventionally used markers are damaged or even 
destroyed by these mechanical stresses. 
Furthermore, wire ropes are often treated with greases, lubricating agents 
or impregnating agents during use, and, of course, the markers must not be 
attacked by these substances. The lubricating and impregnating agents also 
cause the metal dust forming due to the mechanical stress to adhere. 
Consequently, the wire ropes turn black after a short time of use, and 
often the color of the marker is no longer recognizable. The steel dust in 
turn causes mechanical stresses which in many cases are not sustained by 
the conventional markers. 
Under normal operating conditions, the wire ropes generally reach 
temperatures of about 100.degree. C., but under extreme stresses, 
temperatures up to 200.degree.-300.degree. C. can occur. At these 
extremely high temperatures, conventionally used markers are frequently 
stained or charred. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the present invention to provide an improved 
wire rope having a marker. A specific object of the invention is to 
provide a wire rope having a marker which is durably resistant to 
mechanical stresses, chemical influences, including, e.g., seawater, and 
high temperatures. 
In accomplishing the foregoing objects, there has been provided according 
to the present invention a wire rope having a durable marker comprising a 
rope core comprised of a plurality of strands; a plurality of strands 
twisted together around the rope core; and a durable marker comprising a 
tape carrying marking information, the tape being worked into the strands 
of the wire rope in the direction of the longitudinal axis. Preferably, 
the tape is wound around a support element in spirally overlapping manner 
and is located between individual bundles of strands so as to be worked 
into the wire rope at the same twisting angle as the strands. 
Further objects, features and advantages of the present invention will 
become apparent from the detailed description of preferred embodiments 
which follows.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The marker incorporated in the wire rope of the present invention is a 
plastic tape having a width of from about 2 to 6 mm, preferably of from 
about 3 to 4 mm and a thickness of from about 10 to 100 .mu.m, preferably 
of from about 50 to 100 .mu.m. This plastic tape is wound around a support 
element in a spirally overlapping manner. Thus, improved strength values 
are obtained. 
The plastic tape preferably is made of a stretch-oriented polyethylene 
terephthalate film, but it is also possible to use a polyamide, a 
polyolefin or a polyurethane film for its production. Stretching can be 
carried out monoaxially or biaxially. The film has been provided with an 
impression containing all necessary information. The abrasion and shear 
strength of this impression is higher than about 0.5 N/15 mm of film 
width. When a strip of a conventional adhesive tape is pressed onto the 
imprinted area and quickly yanked off again, the impression must not be 
destroyed. 
The materials used for the support element preferably are glass fibers or 
metal wire. However, fibers of polyester, polyimide, carbon or 
combinations of these materials can also be employed. The support element 
has a diameter of from 100 to 200 .mu.m, its minimum tear resistance is 
about 400 N/mm.sup.2. 
In further embodiments, the marker comprising a plastic tape and a support 
element may additionally be provided with a lacquer or metal coating. The 
marker is located in one of the longitudinally extending gaps between the 
individual bundles of strands, and is worked into the wire rope at the 
same twisting angle as the strands. 
Wire ropes suitable for use in the present invention are in general 
comprised of a plurality of strands which are twisted together, each 
strand being composed of a number of concentrical layers of single wires 
which are also twisted together. In particular, the wire ropes comprise a 
very rigid core made of steel wires possessing a high tensile strength. 
This core is surrounded by a plurality of strands, the wires of which have 
a lower tensile strength, but a greater flexibility than the wires of the 
core. 
The tensile strength of the core should in general amount to at least half 
the value measured for the entire rope, and preferably it should amount to 
between 60 to 75% of the tensile strength of the entire rope. 
The wire rope of this invention has the advantage that, under normal 
operating conditions, the information contained on the plastic tape, such 
as, e.g., date of production, qualitative characteristics, and possible 
technical applications, is visible and clearly recognizable even after a 
long period of use. In addition, the mutual shifting of the strands is 
facilitated by the marker of plastic material, due to which the elasticity 
and resistance to corrosion of the wire rope are improved. 
The invention is illustrated in detail by the attached drawings. 
FIG. 1 shows a perspective, cross-sectional view of the wire rope of this 
invention, wherein 1 denotes a strand, 2 denotes the steel core and 3 
denotes the marker. 
FIG. 2 shows a perspective, cross-sectional view of the marker 3 of the 
invention, including the support element 4 and the plastic tape 5 wound 
around the support element 4 in spirally overlapping manner.