CROSS-REFERENCE TO RELATED APPLICATIONS
None.
BACKGROUND OF THE INVENTION
Traditionally, theater production companies use 7×19 or 19×7 wire ropes for stage rigging applications to move actors around the stage. Such wire ropes are usually bright and reflect light so theater production companies or rope manufacturers will often coat the bright wire ropes with black powder to prevent the audience from easily detecting the ropes when used on performers. However, coating the rope with black powder often results in the black powder flaking off during the operation of the rope in the rigging system of pulleys and blocks commonly used in theater productions. Therefore, it would be beneficial to produce a wire rope for use in theatrical productions that has a blackened finish that will not wear or flake off during normal use of the ropes.
Traditional 7×19 or 19×7 wire ropes tend to rotate when under a tensile load which can result in dangerous conditions for performers. A “birdcage” failure of wire rope occurs when the outer strands of a rope balloon outwards taking the shape of a birdcage. This is sometimes due to shock loading. This birdcage effect exposes the core of the wire rope or allows it to pop or move out of position which can be dangerous for the performers. In addition, traditional ropes are subject to excessive rotation thereby rendering them unsuitable for use with swivels attached to the ends of the rope. Such swivels are often used in single part lifts in theatrical productions. Therefore, it would be beneficial to produce a birdcage-resistant and/or a rotation-resistant rope for use in theatrical productions.
Finally, in most theatrical productions, the actors wear elaborate and expensive costumes. If any kind of lubricant is added to the wire rope, the lubricants can rub off and ruin the costumes. However, wire rope will rust rapidly if not lubricated and, in turn, cause premature fatigue failure. Therefore, it would be beneficial to produce a non-lubricated wire rope that will not rust rapidly.
SUMMARY OF THE INVENTION
The present invention is directed to a wire rope having a blackened finish designed for theatrical productions. The wire rope includes a plurality of strands that have a closed spiral arrangement with each other and are compacted. Each strand includes a center wire spirally surrounded by a plurality of inner wires that are spirally surrounded by a plurality of outer wires so that the outer wires completely encompass the inner wires. The center wire and the inner wires are made from a galvanized material and coated with a lubricant. The outer wires are made from a non-coated steel material. Each strand is compacted so the outer wires create a tight mechanical seal to protect the inner wires. The blackened finish on the wire rope is provided by a black oxide coating treatment and provides for low visibility of the wire rope during theatrical performances.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description. Certain embodiments of the invention are outlined above in order that the detailed description thereof may be better understood, and in order that the present contributions to the art may be better appreciated. In this respect, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention, It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. Though some features of the invention may be claimed in dependency, each feature has merit when used independently.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
Further features of the present invention will become apparent to those skilled in the art to which the present invention relates from reading the following description with reference to the accompanying drawings, in which:
FIG. 1 is a side elevational view of one embodiment of the wire rope in accordance with one embodiment of the present invention;
FIG. 2 is a cross-sectional view of one embodiment of a single strand used to construct the wire rope in accordance with one embodiment of the present invention;
FIG. 3 is a cross-sectional view of the single strand of the wire rope of FIG. 1 after compaction in accordance with one embodiment of the present invention;
FIG. 4 is a cross-sectional view of four strands used to construct the entire wire rope in accordance with one embodiment of the present invention;
FIG. 5 is a cross-sectional view of the four strands of FIG. 3 after compaction in accordance with one embodiment of the present invention; and
FIG. 6 is a flow diagram of a method of making the four strands and the entire wire rope in accordance with one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. For purposes of clarity in illustrating the characteristics of the present invention, proportional relationships of the elements have not necessarily been maintained in the drawing figures.
A four-strand wire rope 30 embodying various features of the present invention is shown in FIG. 1. Rope 30 is ideal for use in theatrical stage rigging applications although one skilled in the art will appreciate that rope 30 may also be useful in other application including, but not limited to, mobile crane hoist rope, helicopter rescue hoist rope, marine mooring lines and marine towing lines. In one embodiment, rope 30 is constructed in a substantially rotation-resistant 4×31 configuration. One skilled in the art will appreciate that rope 30 may also be useful other configurations including, but not limited to, 4×19, 4×26, 4×36, 4×41, 4×49 and similar configurations. Rope 30 is coated with a blackened finish for low visibility during theatrical performances.
In a first embodiment, shown in FIG. 2, a strand 10 includes a center wire 12 surrounded by eighteen inner wires 16. Center wire 12 and inner wires 16 are generally cylindrical and are constructed from high-carbon steel drawn to size galvanized wires which have a thin zinc coating. Rope 30 may have a diameter ranging from about ⅛ inch to ⅝ inch. Center wire 12 and inner wires 16 are drawn with a dry, solid lubricant 20, such as, for example, wax, molybdenum disulfide powder, graphite powder, boric acid powder, polytetrafluoroethylene tape or coating, and other appropriate lubricants. Lubricant 20 provides for internal lubrication between center wire 12 and inner wires 16, between inner wires 16, and between inner wires 16 and outer wires 22. Alternatively, center wire 12 and inner wires 16 may be constructed from corrosion-resistant materials or other appropriate materials that include a corrosion-resistant coating and then lubricant 20 is applied to an outer surface 14 of center wire 12 and to outer surfaces 18 of inner wires 16. Spaces 22 are located between center wire 12 and inner wires 16. As shown in FIG. 2, twelve outer wires 22 completely surround inner wires 16. Outer wires 22 are constructed from non-coated high-carbon steel. Center wire 12, inner wires 16, and outer wires 22 are used to produce strand 10 using a known stranding process. Once strand 10 is made, it is compacted using a known in-line compaction method. In one embodiment, stranding and compacting wires 12, 16 and 22 occurs simultaneously using known processes. Because rope 30 is often used to suspend performers wearing delicate and expensive costumes during theatrical performances, it is undesirable for outer wires 22 to contain any type of liquid or gel-like lubrication, as those types of lubrication can stain and ruin the costumes. Therefore, outer wires 22 that form rope 30 of the present invention are produced substantially without any liquid or gel-like lubrication. However, a lack of lubrication can cause premature red rust formation on wires 16. In order to substantially eliminate this problem, center wire 12 and inner wires 16 are made from drawn-galvanized high-carbon steel wires that have a thin zinc coating and are coated with lubricant 20. Additionally, lubricant 20 may be applied by baking it on the wires or spraying it on the wires and letting it dry at room temperature.
FIG. 3 illustrates strand 10 in a compacted state. The compaction of strand 10 flattens (plastically deforms and shapes) outer wires 22 in a manner that creates a mechanical seal 26 thereby creating a tight barrier so that liquids, chemicals or other gels cannot penetrate to inner wires 16. The compaction of strand 10 deforms center wire 12 and inner wires 16. Lubricant 20 is pressed in between and generally fills all of spaces 24 between center wire 12 and inner wires 16, between inner wires 16, and between inner wires 16 and outer wires 22.
FIG. 4 illustrates rope 30 having four strands 10a, 10b, 10c, and 10d respectively and having a spiral arrangement. Strands 10a, 10b, 10c, and 10d have been stranded and compacted and are closed together to produce rope 30. Rope 30 is rotation-resistant. In the embodiment illustrated in FIGS. 1-5, wire rope 30 is formed using four compacted strands. To produce rotation resistant were ropes, a plurality of strands 10 are helically-laid around a center (not shown) that may be an additional wire or may be empty space as shown in FIGS. 4 and 5. It will be appreciated by one skilled in the art that wire rope 30 may comprise three, four or more strands arranged in a spiraled arrangement.
FIG. 5 illustrates rope 30 after compaction. Rope 30 undergoes a compaction process such as, for example, swaging or roller die compaction that further compacts rope 30. After compaction, rope 30 undergoes a black oxide coating treatment. Any black oxide coating method may be used, such as, for example, cold applied, low temperature, standard high temperature or other appropriate black oxide coating method now known or that may be known in the future. In order to eliminate the problem of flaking that can occur when the blackening is done through a powder coat treatment, the blackened finished of rope 30 occurs through a black oxide chemical conversion process. This process may be adversely affected if the black oxide chemical is contaminated by zinc contained in inner wires 16. Therefore, it is important that inner wires 16 containing zinc are not exposed to the chemicals used in the black oxide treatment. As described hereinabove, this is accomplished by first compacting each strand 10. The compaction of strand 10 causes the flattening (plastic deformation and shaping) of outer wires 22 and cause outer wires 22 to butt up (wedge) against one another thereby forming tight mechanical seal 24 and preventing the liquid black oxide chemical from coming into contact with inner wires 16. The blackened finish decreases the visibility of rope 30 for use in theatrical stage productions.
FIG. 6 is a flow diagram of one embodiment of the present invention of a method of making wire rope 30 where the individual configurations of wire rope 30 are illustrated in FIGS. 1-5. The method of producing wire rope 30 of the present invention involves several steps. In step 40, galvanized center wire 12 and inner wires 16 are produced and lubricant 20 is applied to outer surface 14 of center wire 12 and outer surfaces 18 of inner wires 16. In step 40, non-coated steel outer wires 22 are also produced. Step 42 is an optional heat treatment that may be applied to center wire 12 and inner wires 16 to both stress-relieve wires 12 and 16, and bake solid lubricant 18 to outer surface 14 of center wire 12 and outer surfaces 18 of inner wires 16. In step 44, center wire 12, eighteen inner wires 16 and twelve outer wires 22 are used to produce strand 10 in a normal stranding process. In step 46, each strand 10 is compacted using an in-line compaction method. The compaction of strand 10 flattens outer wires 22 in a manner were outer wires 22 provide mechanical seal 26 thereby creating a barrier so that the liquid chemicals used in step 52 in the blackening process cannot penetrate to inner wires 16 of strand 10. In step 48, wire rope 30 is produced by closing four strands 10a, 10b, 10c, and 10d. In step 50, wire rope 50 is compacted. In step 52, a blackened finish is applied to wire rope 30 by a black oxide conversion process in either an in-line process or a batch process.
The resultant wire rope 30 is a high-strength, rotation-resistant, birdcage-resistant, corrosion-resistant wire rope with a blackened finish that will not flake off during the operation of the rope in a rigging system of blocks and pulleys.
In an alternate embodiment that is not shown, standard end fittings can then be attached to the ends of wire rope 30 to produce various fabricated assemblies for use in stage rigging applications. Optionally, the end fittings can also be blackened as needed.
From the foregoing, it will be seen that this invention is one well adapted to attain all ends and objects hereinabove set forth together With the other advantages -which are obvious and which are inherent to the structure.
It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.
Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative, and not in a limiting sense.
Patent Application
20120085077
