Techniques for making non-halogenated flame retardant polyolefin tape for use in a cable

Abstract

A tape manufacturing system includes an extruder having a die that defines an elongated opening. The extruder provides molten NHFR polyolefin material through the die. The system further includes a cooling assembly, coupled to the extruder, that receives the extruded NHFR polyolefin material from the extruder and cools the extruded NHFR polyolefin material so that the extruded NHFR polyolefin material hardens into a contiguous sheet, and a cutting assembly that receives the contiguous sheet and cuts the contiguous sheet lengthwise to form multiple parallel feeds of NHFR polyolefin tape. The extruder, the cooling assembly and the cutting assembly operate simultaneously in a continuous manner so that the sheet of NHFR polyolefin material is unbroken between the cooling assembly and the cutting assembly. In general, the system is cost effective since multiple, unlimited length feeds of NHFR polyolefin tape can be made at the same time.

Description

BACKGROUND OF THE INVENTION

[0001] A typical communications or power cable is capable of carrying a communications signal or electrical current from one end to the other. Some communications or power cables (hereinafter, generally referred to as cables) include one or more conductors (e.g., twisted pairs or fiber optic elements) for carrying multiple communications signals or electrical currents simultaneously. Such cables typically include an outer jacket that physically protects and insulates the cable conductors from damage (e.g., from splitting when hit, from the negative affects of smoke, flame, humidity, etc.). Often, the outer jacket of the cable is a plastic-based polymer which is applied around the cable conductors in molten form (e.g., using an extrusion process).

[0002] In order to protect the cable conductors against heat-related damage when the outer jacket of the cable is applied, cable manufacturers often wrap insulating tape around the cable conductors prior to the jacketing process. The insulating tape shields the conductors against severe heat stresses that would otherwise damage the conductors, e.g., that would otherwise melt the insulation around individual conductors potentially causing undesired shorts, fatigue, etc. Examples of insulating tape include polyester tape and fluoropolymer tape (such as Teflon™).

[0003] Some cables are flame retardant. For example, one type of cable is called plenum cable which is installed within building plenums (e.g., the spaces above dropped ceilings, wall cavities, etc.). Cable manufacturers often wrap the plenum cable conductors with flame retardant tape because it adequately shields the conductors during the jacketing process and, once installed, will not contribute to the spread of flames if the building is on fire. Also, flame retardant tapes help protect the conductors from the flames and thus keep the cable functional during a fire for a longer period than cables wrapped in tapes which are not flame retardant. Keeping the lights on, maintaining signals to and from alarm systems, maintaining signals to controls in aircraft, subways, etc., and keeping telecommunications equipment operational are examples how making cables last longer in a fire can be of critical importance. In some parts of the world, flame retardant cable is required by code.

[0004] Traditional flame retardant tapes use halogenated materials to generate smoke when they burn. This smoke then smothers flames, making the tapes self-extinguishing. Halogenated materials contain halogens such as chlorine, fluorine, and bromine which give off toxic fumes when burned, i.e., fumes that are harmful, or even fatal, to people.

[0005] Some cable manufacturers make cables that use a fluoropolymer tape. Flouropolymer is a non-halogenated material, i.e., a material that is substantially free of halogens. Examples of cables which use flouropolymer tape include communications and power cables for buildings, aircraft, ships, subways, etc. Increasingly, in some parts of the world, cable which is substantially free of halogens is required by code. Teflon™ tape is an example of flouropolymer tape.

[0006] There are multiple conventional approaches to making fluoropolymer tape. One conventional approach to making fluoropolymer tape (hereinafter called the skiving approach to making fluoropolymer tape) is to (i) form a large solid cylinder-shaped portion of fluoropolymer and (ii) shave or “skive” off a fluoropolymer sheet from the surface of this cylinder as the cylinder rotates. The fluoropolymer sheet is then wound into a roll, and subsequently moved to a cutting assembly. At the cutting assembly, the fluoropolymer sheet is unrolled and passed through a row of blades which divide the sheet into multiple runs of fluoropolymer tape which can be wound onto smaller winders. Later, the fluoropolymer tape can be unwound and wrapped around a set of conductors to protect those conductors during the jacketing process.

[0007] Another conventional approach to making fluoropolymer tape (hereinafter called the extruded fluoropolymer sheet approach) involves extruding fluoropolymer into a fluoropolymer sheet. Due to the high melting point of fluoropolymer (e.g., greater than 500 degrees Fahrenheit), the extruded fluoropolymer sheet is then cooled extensively and wound into a roll. The roll of fluoropolymer sheet is later unwound at a cutting assembly, cut into multiple runs of fluoropolymer tape, and wound on smaller winders for subsequent use as conductor wrapping.

[0008] Some communications or power cables include a feed or “run” of separating material having an X-shaped cross-section which runs centrally through the space of the cable jacket and which divides that space into four cavities. This separating material physically separates four conductors, or pairs of conductors, respectively running through the four cavities in order to improve signal isolation. An example of such a cable is a conventional Category 6 cable which uses, as the separating material, a run of non-halogenated flame retardant (NHFR) polyolefin having an X-shaped cross-section.

[0009] A conventional approach to making the above-described run of X-shaped NHFR polyolefin separating material (hereinafter called the extruding approach to making X-shaped NHFR polyolefin separating material) is to extrude the NHFR polyolefin material through an X-shaped profile die to form a run of X-shaped NHFR polyolefin separating material. The run is then cooled and wound into rolls so that it can be later combined with conductors or pairs of conductors and a cable jacket to form a communications or power cable having improved signal isolation.

SUMMARY OF THE INVENTION

[0010] Unfortunately, there are deficiencies to the above-described conventional approaches to making fluoropolymer tape and the X-shaped NHFR separating material. For example, in the above-described conventional skiving approach to making fluoropolymer tape, there is a restriction on the length of the fluoropolymer tape. In particular, the length of the fluoropolymer tape is limited by the length of the fluoropolymer sheet which can be skived from the solid cylinder of fluoropolymer. The length of the fluoropolymer sheet is, in turn, limited by the diameter of the cylinder that can be made of fluoropolymer. Beyond a particular diameter, the skiving process becomes impractical due to physical stresses placed on the cylinder of fluoropolymer (e.g., distortion, compression, stretching, etc. due to its own weight). Similarly, in the above-described conventional extruded fluoropolymer sheet approach, the length of the fluoropolymer tape is limited by the length of the extruded fluoropolymer sheet which is wound into a roll before being moved to a cutting assembly. That is, the fluoropolymer tape, which is cut from the extruded fluoropolymer sheet, ends when the extruded fluoropolymer sheet ends. The extruded fluoropolymer sheet typically is not made very long since the weight of a long fluoropolymer sheet would tend to affect the physical properties of the fluoropolymer sheet (e.g., distort, stretch, compress, etc.).

[0011] Nevertheless, cable manufacturers often prefer to purchase long lengths of tape in order to minimize the number of occasions in which the tape ends. Upon such occasions, cable manufacturers typically splice the end of a new tape to the end of the initial tape in order to continue manufacturing a length of that cable, or alternatively terminate manufacturing of that cable. In the former situation, the splice poses a weak point in the cable, i.e., a point which is more prone to failure (e.g., breaking, improperly shielding against heat, etc.). In the latter situation, the cable manufacturer is left with a length of cable that is shorter than initially intended thus wasting materials at the point where most of the value has already been added (i.e., after individual conductors have been made, twisted, run with other conductors, jacketed, etc).

[0012] In addition to restrictions on the length of fluoropolymer tape which the above described conventional methods are capable of making, the manufacturing processes are generally expensive and an inefficient use of resources. That is, a significant amount of resources (high temperature paste extruders, cooling equipment, skiving equipment, multiple process steps, relatively expensive raw materials, etc.) must be invested to manufacture fluoropolymer tape. In some instances, the cost for such resources makes this product prohibitively expensive. Moreover, firefighters must be particularly cautious when attending to fires in buildings that contain high amounts of flouropolymer tape since flouropolymer tape has a high melting temperature (e.g., the melting point of some Teflons™ is greater than 600 degrees Fahrenheit) and tends to drip. Firefighters can sustain serious injuries if molten flouropolymer drips onto and melts through their protective gear.

[0013] Additionally, in the above-described extruding approach to making X-shaped NHFR separating material, the manufacturing process is expensive and an inefficient use of resources. That is, a significant amount of resources (extruding equipment, cooling equipment, winding equipment, etc.) must be invested to extrude and wind a single length of the X-shaped NHFR separating material. In some instances, the cost for such resources makes this approach prohibitively expensive.

[0014] In contrast to the above-described conventional approaches to making fluoropolymer tape and the X-shaped NHFR separating material, the invention is directed to techniques for making NHFR polyolefin tape for cable using a process which involves extruding a NHFR polyolefin sheet, cooling the sheet and cutting the sheet to form multiple parallel feeds of NHFR polyolefin tape in a continuous manner. Accordingly, breaks in the sheet can be avoided and the length of each feed of NHFR polyolefin tape is essentially unlimited. As a result, extremely large lengths of tape can be provided to cable manufacturers enabling the cable manufacturers to make extremely long lengths of cable without any tape splices which otherwise would become possible points of failure. In addition, this is an efficient and cost effective use of resources because the tapes are made in a continuous process and using polyolefin base materials which are relatively less expensive than fluoropolymer base materials.

[0015] One embodiment of the invention is directed to a NHFR polyolefin tape manufacturing system for making NHFR polyolefin tape. The NHFR polyolefin tape manufacturing system includes an extruder having a die that defines an elongated opening. The extruder provides molten NHFR polyolefin material through the die. The NHFR polyolefin tape manufacturing system further includes (i) a cooling assembly, coupled to the extruder, that receives the extruded NHFR polyolefin material from the extruder and cools the extruded NHFR polyolefin material so that the extruded NHFR polyolefin material hardens into a contiguous sheet of NHFR polyolefin material, (ii) a cutting assembly that receives the contiguous sheet of NHFR polyolefin material and cuts the contiguous sheet of NHFR polyolefin material lengthwise to form multiple parallel feeds of NHFR polyolefin tape, and (iii) a winding assembly that winds the multiple parallel feeds of NHFR polyolefin tape into either traverse wound rolls called spools (i.e. winding back and forth to make a roll like a spool of thread) or single wound rolls called pads (i.e. winding each wrap on top of the previous wrap to make a roll like a roll of masking tape). The extruder, the cooling assembly, the cutting assembly, and the winding assembly operate simultaneously in a continuous manner so that the sheet of NHFR polyolefin material is unbroken between the cooling assembly and the winding assembly. The tape manufacturing system is cost effective since multiple rolls of NHFR polyolefin tape can be made at the same time in a continuous manufacturing process. Additionally, because the tape can be traverse wound on a winder, this system can produce extremely long lengths of polyolefin tape with no splices. As such, the length of the tape is not limited to the length of a fluoropolymer sheet as in the earlier-described conventional approaches which form fluoropolymer tape by unrolling a fluoropolymer sheet from a roll and cutting the fluoropolymer sheet.

[0016] In one arrangement, the tape manufacturing system further includes a winding assembly that simultaneously winds each of the multiple parallel feeds on a respective winder to form multiple rolls of NHFR polyolefin tape. In this arrangement, each roll can include a non-spliced feed of NHFR polyolefin tape that is at least 2,500 feet in length (e.g., 25,000 foot lengths, 40,000 foot lengths, etc.) thus enabling cable manufacturers to reduce the number of tape splices (potential failure points) in their manufacturing process, and/or avoid making short lengths of cable.

[0017] In one arrangement, the die of the extruder defines the elongated opening such that the elongated opening has a rectangular shape which is at least 150 times longer in length than in width. Accordingly, many feeds of tape can be manufactured simultaneously (e.g., by cutting the extruded sheet lengthwise into multiple feeds) thus increasing output and efficiently using resources.

[0018] In one arrangement, the tape manufacturing system further includes a drying assembly, coupled to the extruder, that dries the NHFR polyolefin compound to extract moisture from the NHFR polyolefin compound, and provides the dried NHFR polyolefin compound to the extruder. This arrangement decreases moisture in the compound that would otherwise promote bubbles in the extruded sheets of NHFR polyolefin material and possibly render the extruded sheets less usable or unusable.

[0019] In one arrangement, the tape manufacturing system further includes an orientation and annealing assembly, disposed between the cutting assembly and the winding assembly, that orients and anneals the feeds of NHFR polyolefin material in a lengthwise direction to orient molecules within the NHFR polyolefin material such that tensile strength of the feeds is greater in the lengthwise direction than in a widthwise direction. This arrangement increases the strength of the NHFR polyolefin feeds in the lengthwise direction which may be desirable when the tape is used to wrap wires, and which may enable the production of longer tapes using less material.

[0020] Another embodiment of the invention is directed to a cable manufacturing system for making a cable. The cable manufacturing system includes a conductor source that provides a set of conductors which are capable of carrying at least one communications signal or electrical current, an NHFR polyolefin tape source that provides NHFR polyolefin tape, a feed assembly that wraps the NHFR polyolefin tape around the conductor or set of conductors, and an extruding assembly that extrudes a jacket around the wrapped set of conductors to form the cable. The earlier described tape manufacturing system is suitable for use as the NHFR polyolefin tape source for the cable manufacturing system.

[0021] The features of the invention, as described above, may be employed in manufacturing systems and methods for making NHFR polyolefin tape, as well as various products which use such tape, such as those of Film X, Inc. of Dayville, Conn.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

[0023] FIG. 1 is a block diagram of an NHFR polyolefin tape manufacturing system which is suitable for use by the invention.

[0024] FIG. 2 is a diagram of various materials which are used and/or provided by the NHFR polyolefin tape manufacturing system of FIG. 1.

[0025] FIG. 3 is a perspective view of an extruder die of the NHFR polyolefin tape manufacturing system of FIG. 1.

[0026] FIG. 4 is a flowchart of a procedure performed by the NHFR polyolefin tape manufacturing system of FIG. 1 to make multiple rolls of simultaneously wound NHFR polyolefin tape.

[0027] FIG. 5 is a block diagram of a cable manufacturing system which is suitable for use by the invention.

[0028] FIG. 6 is a perspective view of various portions of an electronic or fiber optic communications cable or power cable which is produced by the cable manufacturing system of FIG. 5.

[0029] FIG. 7 is a flowchart of a procedure performed by the cable manufacturing system of FIG. 5 to make the electronic or fiber optic communications or power cable of FIG. 6.

DETAILED DESCRIPTION

[0030] The invention is directed to techniques for making non-halogenated flame retardant polyolefin tape (NHFR) which is suitable for use in communications or power cable by employing a process that involves extruding a NHFR polyolefin sheet, cooling the sheet and cutting the sheet to form multiple parallel feeds of NHFR polyolefin tape in a continuous manner. In general, since the sheet can be endless, the length of each feed of NHFR polyolefin tape is essentially unlimited. As a result, extremely large lengths of tape can be provided to cable manufacturers enabling the cable manufacturers to make extremely long lengths of cable without any tape splices which otherwise could become weak points (i.e., points of failure).

[0031] FIG. 1 shows a NHFR polyolefin tape manufacturing system 20 which is suitable for use by the invention. The NHFR polyolefin tape manufacturing system 20 is capable of simultaneously making multiple rolls 22 of NHFR polyolefin tape 24. The system 20 includes several stages which are arranged in a pipelined manner. In particular, the system 20 includes a drying/mixing assembly 26, an extruder 28, an extruding die 30, a cooling assembly 32, a cutting assembly 34, an orienting and annealing assembly 36, and a winding assembly 38. Each roll 22 includes a single feed of NHFR polyolefin tape 24 and a core 40 upon which that feed of tape 24 is wound. Further details of how the system 20 operates will now be provided with reference to FIGS. 1 through 4.

[0032] FIG. 2 shows various materials which are used and/or provided by the NHFR polyolefin tape manufacturing system 20 of FIG. 1. As shown in FIGS. 1 and 2, NHFR polyolefin compound 42 is a raw material used by the system 20. In one arrangement, the NHFR polyolefin compound 42 includes a polyolefin resin carrier such as polypropylene and an NHFR mineral filler such as magnesium hydroxide. The drying/mixing assembly 26 can receive the compound 42 in a premixed state, or receive the components individually and combine them together to form the compound 42 (e.g., physically stir) in controlled and specified proportions (e.g., in 50/50 proportions). Additionally, the drying/mixing assembly 26 blows heated air through the compound 42 to remove moisture from the compound 42 thus reducing the likelihood of forming bubbles in subsequent manufacturing stages which could interfere in production of the multiple rolls 22 of NHFR polyolefin tape 24.

[0033] The drying/mixing assembly 26 provides dried NHFR polyolefin compound 44 to the extruder 28 which grinds and further mixes the dried NHFR polyolefin compound 44 into molten NHFR polyolefin material 46 (see FIG. 1). In one arrangement, the compound 44 is in pelletized form, and a rotating auger of the extruder 28 uses friction and heat to eventually melt compound 44 into the molten NHFR polyolefin material 46.

[0034] Next, the extruder 28 pushes the molten NHFR polyolefin material 46 through an extruding die 30 that defines an elongated opening to form a liquid sheet 48 of NHFR polyolefin material. FIG. 3 shows a die 60 which is suitable for use as the extruding die 30. The die 60 includes a first side member 61-A and a second side member 61-B which are fastened together to form an elongated opening 62. Preferably, the opening has a length 64 which is at least 150 times greater than its width 66 in order to provide a wide liquid sheet 48 of NHFR polyolefin material (e.g., a maximum width of 0.02 inches and a length greater or equal to 3.00 inches). In one arrangement, the die 60 is located such that the elongated opening 62 points in a downward direction 68 such that the liquid sheet 48 drops (e.g., due to gravity) into a liquid cooling bath of the cooling assembly 32.

[0035] The cooling assembly 32 (see FIG. 1) cools the liquid sheet 48 so that it hardens into a solid NHFR polyolefin sheet 50. In one arrangement, the cooling assembly 32 includes a tank that holds a cooling bath which receives the liquid sheet 48. When the sheet 48 travels through the cooling bath, the sheet 48 hardens as its temperature drops. As the hardened NHFR polyolefin sheet 50 (see FIG. 2) exits the cooling assembly 32, vacuum rollers remove excess liquid from the sheet 50. An alternative arrangement has a cooling assembly with a chilled roller in place of the cool liquid bath. The liquid NHFR polyolefin sheet is extruded onto the chilled roller which cools and hardens the liquid sheet as its temperature drops.

[0036] Next, the cutting assembly 34 cuts the sheet 50 into multiple parallel feeds 52. In one arrangement, the cutting assembly 34 includes a row of blades mounted in fixed positions so that the resulting feeds 52 have defined (e.g., uniform) widths. An example range of widths for each feed 52 is between 0.125 to 2.000 inches.

[0037] The orienting and annealing assembly 36 then orients and anneals the NHFR polyolefin feeds 52 and brings the NHFR polyolefin feeds 52 to a finished state 54. In one arrangement, the orientation and annealing assembly 36 includes multiple rollers which (i) rotate at varying speeds and (ii) provide varying temperatures. Accordingly, as the feeds 52 pass around these rollers, the surfaces of the rollers stretch the feeds 52 to a desired width, thickness, and tensile strength. In one arrangement, the feeds 52 are not substantially stretched thus leaving the feeds 52 with a fairly uniform tensile strength in both the lengthwise and widthwise directions. In another arrangement, the feeds 52 are substantially stretched in the lengthwise direction to increase the strength of the feeds 52 (e.g., by orienting molecules within the feeds 52) in the lengthwise direction over that in the widthwise direction. Such stretching also tends to narrow and thin out the feeds 52 thus increasing the length of the feeds 52 without requiring additional material. The orientation and annealing assembly 36 provides resulting oriented and annealed feeds 54 to the winding assembly 38. Examples of thicknesses for the finished feeds 54 include 0.002, 0.003, 0.005, 0.010, 0.015, and 0.020 inches.

[0038] Next, the winding assembly 38 winds the multiple parallel feeds 54 onto cores 40 to form the multiple rolls 22 of NHFR polyolefin tape 24. The feeds 54 extend in a side-by-side manner from the cutting assembly 34 or the orienting and annealing assembly 36 to the winding assembly 38. In one arrangement, each feed 54 passes through a series of eyelets which guide that feed 54 onto a respective winder 38 and core 40. In one arrangement, the feeds 54 of tape 24 roll onto cores 40 which are substantially wider than the feeds so that the feeds 54 can traverse wind onto the cores 40 in a side-to-side manner to form, as the multiple rolls 22, spools of NHFR polyolefin tape 24, i.e., like a spool of thread (see FIGS. 1 and 2). In another arrangement, the feeds 54 wind onto cores 40 in a reel-like manner to form, as the multiple rolls 22, a set of pads or “pancakes” of NHFR polyolefin tape 24, i.e. like a roll of masking tape.

[0039] FIG. 4 shows a flowchart summarizing a procedure 70 performed by the NHFR polyolefin tape manufacturing system 20 to make the multiple rolls 22 of simultaneously wound NHFR polyolefin tape 24. In step 72, the drying/mixing assembly 26 of the system 20 dries and mixes the NHFR polyolefin compound 42 to extract moisture and mix the constituent materials thus forming the dried NHFR polyolefin compound 44. In step 74, the extruder 28 uses friction and heat to melt the dried/mixed compound 44 into the molten NHFR polyolefin material 46. In step 76, the extruder 28 extrudes the molten NHFR polyolefin material 46 through an extruding die 30 that defines an elongated opening to form a liquid sheet 48 of NHFR polyolefin material. In step 78, the cooling assembly 32 cools the liquid sheet 48 so that it hardens into a contiguous solid sheet 50 of NHFR polyolefin material. In step 80, the cutting assembly 34 cuts the sheet 50 lengthwise to form multiple parallel feeds 52 of NHFR polyolefin tape 24. In step 82, the orienting and annealing assembly 36 stretches the feeds 52 in a lengthwise direction and heats and cools them to form oriented and annealed feeds 54. In step 84, the winding assembly 38 simultaneously winds each of the multiple parallel feeds 54 on a respective core 40 to form the multiple rolls 22 of the NHFR polyolefin tape 24.

[0040] It should be understood that the steps 72 through 84 of the procedure 70 are preferably continuously performed as a set of ongoing steps 86 so that each feed 54 is essentially unlimited in length. That is, as long as the system 20 continues operating, there is no limit to the length of each feed 54 of NHFR polyolefin tape 24. As a result, extremely large lengths of tape 24 can be produced, and such lengths can be provided to cable manufacturers enabling the cable manufacturers to make extremely long lengths of cable without any tape splices which otherwise would become possible points of failure.

[0041] It should be further understood that manufacturing the NHFR polyolefin tape 24 is generally less expensive and less complex to make than manufacturing conventional flouropolymer tape. In particular, the raw materials for the NHFR polyolefin tape 24 are typically more available (e.g., less expensive) than that for flouropolymer tape. Additionally, due to a generally lower melting point for the NHFR polyolefin tape 24, the intermediate products are typically easier to handle than intermediate flouropolymer products (i.e., molten NHFR polyolefin requires less cooling and thus less handling equipment than that for molten flouropolymer). Moreover, because of the continuous nature of the procedure 70 it is a cost effective use of resources (e.g., no need to wind and unwind cut sheets) compared to the conventional process of making fluoropolymer tape. Further details of the invention will now be provided with reference to FIGS. 5 and 6.

[0042] FIG. 5 shows a cable manufacturing system 90 which is suitable for use by the invention. The cable manufacturing system 90 includes a conductor source 92, an NHFR polyolefin tape source 94, a feeding assembly 96, and an extruding assembly 98. The feeding assembly 96 is interconnected between each of the conductor source 92, the NHFR polyolefin tape source 94 and the extruding assembly 98.

[0043] FIG. 6 shows a portion of a cable 100 which can be manufactured by the cable manufacturing system 90 of FIG. 5. The cable 100 includes a set of conductors 102. Each conductor 102 includes central conductive material 104 (e.g., copper, optical fibers, etc.), and outer insulation material 106 (e.g., an extruded polymer). The cable 100 further includes (i) NHFR polyolefin tape 108 which is wrapped around the set of conductors 102 that form a bundle 110 of conductors, and (ii) an outer jacket 112.

[0044] Firefighters may prefer working in buildings having the cable 100 since the cable 100 uses NHFR polyolefin tape 108 rather than conventional flouropolymer tape which in general has a higher melting point. Accordingly, firefighters can be less concerned about flouropolymer melting and dripping onto and through their gear when working in buildings that use the cable 100 in place of cable that uses conventional flouropolymer tape. Further details of the system 90 will now be provided with reference to FIG. 7.

[0045] FIG. 7 shows a procedure 120 which is performed by the cable manufacturing system 90 of FIG. 5 to make the cable 100 of FIG. 6. In step 122, the conductor source 92 provides the set of conductors 102 which are capable of carrying at least one communications signal or electrical current. In step 124, the NHFR polyolefin tape source 94 provides feeds of NHFR polyolefin tape 108. In step 126, the feeding assembly 96 wraps the NHFR polyolefin tape 108 around the set of conductors 102 that form the bundle 110 of conductors. In step 128, the extruding assembly 98 extrudes jacketing material (e.g., a plastic-based substance) around the bundle 110 of conductors to form the jacket 112. Due to the long lengths of the NHFR polyolefin tape 108, the cable manufacturing system 90 is capable of producing long lengths of the cable 100 which are free of tape splices. Accordingly, a cable manufacturer using the system 90 can avoid splices which pose weak points in the cable, i.e., points which are more prone to failure (e.g., breaking the tape, improperly shielding against heat, etc.). Additionally, the cable manufacturer can avoid making undesirable lengths of cable which are shorter than initially intended and which would waste materials particularly at the point where most of the value has already been added (i.e., after individual conductors have been made, twisted, run with other conductors, etc).

[0046] It should be understood that the NHFR polyolefin tape manufacturing system 20 of FIG. 1 is suitable for use as the NHFR polyolefin tape source 94 of the system 90 of FIG. 5. That is, the NHFR polyolefin tape manufacturing system 20 of FIG. 1 is capable of providing extended lengths of NHFR polyolefin tape which can be wrapped around conductors to shield the conductors 102 against excessive heat during the cable jacketing process and to protect conductors from flames during a fire. The NHFR polyolefin tape 108 can be used to form a wrapped bundle of conductors, or wrap a previously formed bundle of conductors.

[0047] It should be further understood that the NHFR polyolefin tape provided by the NHFR polyolefin tape manufacturing system 20 of FIG. 1 was described above as being used in wrapping applications by way of example only. The NHFR polyolefin tape can be used in other applications as well. For example, the NHFR polyolefin tape can be used internally within a cable as a separator tape to provide signal isolation.

[0048] As described above, the invention is directed to techniques for making NHFR polyolefin tape for cable using a process which involves extruding a NHFR polyolefin sheet, cooling the sheet and cutting the sheet to form multiple parallel feeds of NHFR polyolefin tape in a continuous manner. As such, discontinuities in the sheet can be avoided and the length of each feed of NHFR polyolefin tape is essentially unlimited. Accordingly, extremely large lengths of tape can be provided to cable manufacturers enabling the cable manufacturers to make extremely long lengths of cable without any tape splices which otherwise would become possible points of failure. The features of the invention can be used in tape and cable products, manufacturing procedures and systems, and the like, such as those of Film X, Inc. of Dayville, Conn.

[0049] While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

[0050] For example, it should be understood that the various stages of the NHFR polyolefin tape manufacturing system 20 were provided by way of example only. One or more of the stages can be omitted, and one or more other stages can be added. For instance, the orientation and annealing assembly 36 is not required, but useful in some applications such as when producing NHFR polyolefin tape that is stronger in the lengthwise direction. As another example, the drying and mixing assembly 26 is unnecessary if the compound is provided in a premixed and dried state. As yet another example, a step of colorant incorporation can be added during the mixing stage in order to provide the NHFR polyolefin tape with a particular color (e.g., yellow, orange, etc.). As yet another alternative, the drying and mixing assembly 26 can be separated into individual drying and mixing assemblies or stages. As yet another example, an oven can be added between the cutting assembly and the orienting and annealing assembly to heat the tape to facilitate orientation and annealing.

[0051] Additionally, it should be understood that the system 20 was described as providing a smooth sheet of NHFR polyolefin material as an intermediate product by way of example only. Other shapes are suitable for use as well such as a sheet with ribs or protrusions (e.g., using a die having a differently shaped opening) that extend along the length of the sheet such that, when the sheet is cut lengthwise into individual feeds 52 by the cutting assembly 34, each feed 52 has a nonrectangular cross-section (e.g., a “+”-shaped cross-section).

[0052] Furthermore, the cable manufacturing system 90 was described above as making cable which is suitable for carrying communications signals or electrical current by way of example only. It should be understood that the conductors 102,134 of the manufactured cable can have a variety of forms such as metal (e.g., stranded copper, solid copper, bare copper, aluminum, etc.), optical fibers, any combinations thereof, and the like. Moreover, the conductors 102, 134 can carry signals other than communications signals or electrical current (e.g., analog signals, digital signals, etc.) such as intermittent pulses, spikes, etc.

Claims

1. A method for making non-halogenated flame retardant polyolefin tape, comprising the steps of:

extruding molten non-halogenated flame retardant polyolefin material through a die that defines an elongated opening;

cooling the extruded non-halogenated flame retardant polyolefin material SO that the extruded non-halogenated flame retardant polyolefin material hardens into a contiguous sheet of non-halogenated flame retardant polyolefin material; and

cutting the contiguous sheet of non-halogenated flame retardant polyolefin material lengthwise to form multiple parallel feeds of non-halogenated flame retardant polyolefin tape, wherein the steps of extruding, cooling and cutting are performed simultaneously in a continuous manner so that the sheet of non-halogenated flame retardant polyolefin material is unbroken before the step of cutting.

2. The method of claim 1, further comprising the step of:

simultaneously winding each of the multiple parallel feeds on a respective core to form multiple rolls of non-halogenated flame retardant polyolefin tape.

3. The method of claim 2 wherein the step of simultaneously winding includes the step of concurrently forming, as the multiple rolls, multiple spools of non-halogenated flame retardant polyolefin tape.

4. The method of claim 2 wherein the step of simultaneously winding includes the step of concurrently forming, as the multiple rolls, multiple pads of non-halogenated flame retardant polyolefin tape.

5. The method of claim 1 wherein the die defines the elongated opening such that the elongated opening has a rectangular shape which is at least 150 times longer in length than in width, and wherein the step of extruding includes the step of:

pushing the molten non-halogenated flame retardant polyolefin material through the elongated opening having the rectangular shape which is at least 150 times longer in length than in width.

6. The method of claim 1, further comprising the steps of:

drying non-halogenated flame retardant polyolefin compound to extract moisture from the non-halogenated flame retardant polyolefin compound; and

providing the dried non-halogenated flame retardant polyolefin compound to an extruder to form the molten non-halogenated flame retardant polyolefin material for the step of extruding.

7. The method of claim 1, further comprising the step of:

stretching and annealing the feeds of non-halogenated flame retardant polyolefin material in a lengthwise direction to orient molecules within the non-halogenated flame retardant polyolefin material such that tensile strength of the feeds is greater in the lengthwise direction than in a widthwise direction.

8. A roll of non-halogenated flame retardant polyolefin tape made by a method comprising the steps of:

extruding molten non-halogenated flame retardant polyolefin material through a die that defines an elongated opening;

cooling the extruded non-halogenated flame retardant polyolefin material so that the extruded non-halogenated flame retardant polyolefin material hardens into a contiguous sheet of non-halogenated flame retardant polyolefin material;

cutting the contiguous sheet of non-halogenated flame retardant polyolefin material lengthwise to form multiple parallel feeds of non-halogenated flame retardant polyolefin tape, the steps of extruding, cooling and cutting being performed simultaneously in a continuous manner so that the sheet of non-halogenated flame retardant polyolefin material is unbroken before the step of cutting; and

winding a feed of the non-halogenated flame retardant polyolefin tape on a core to form the roll of non-halogenated flame retardant polyolefin tape.

9. A non-halogenated flame retardant polyolefin tape manufacturing system for making non-halogenated flame retardant polyolefin tape, comprising:

an extruder having a die that defines an elongated opening, the extruder providing molten non-halogenated flame retardant polyolefin material through the die;

a cooling assembly, coupled to the extruder, that receives the extruded non-halogenated flame retardant polyolefin material from the extruder and cools the extruded non-halogenated flame retardant polyolefin material so that the extruded non-halogenated flame retardant polyolefin material hardens into a contiguous sheet of non-halogenated flame retardant polyolefin material; and

a cutting assembly that receives the contiguous sheet of non-halogenated flame retardant polyolefin material and cuts the contiguous sheet of non-halogenated flame retardant polyolefin material lengthwise to form multiple parallel feeds of non-halogenated flame retardant polyolefin tape, wherein the extruder, the cooling assembly and the cutting assembly operate simultaneously in a continuous manner so that the sheet of non-halogenated flame retardant polyolefin material is unbroken between the cooling assembly and the cutting assembly.

10. The non-halogenated flame retardant polyolefin tape manufacturing system of claim 9, further comprising:

a winding assembly that simultaneously winds each of the multiple parallel feeds on a respective core to form multiple rolls of non-halogenated flame retardant polyolefin tape.

11. The non-halogenated flame retardant polyolefin tape manufacturing system of claim 10 wherein the winding assembly is configured to concurrently form, as the multiple rolls, multiple spools of non-halogenated flame retardant polyolefin tape.

12. The non-halogenated flame retardant polyolefin tape manufacturing system of claim 10 wherein the winding assembly is configured to concurrently form, as the multiple rolls, multiple pads of non-halogenated flame retardant polyolefin tape.

13. The non-halogenated flame retardant polyolefin tape manufacturing system of claim 9 wherein the die of the extruder defines the elongated opening such that the elongated opening has a rectangular shape which is at least 150 times longer in length than in width.

14. The non-halogenated flame retardant polyolefin tape manufacturing system of claim 9, further comprising:

a drying assembly, coupled to the extruder, that dries the non-halogenated flame retardant polyolefin compound to extract moisture from the non-halogenated flame retardant polyolefin compound, and provides the dried non-halogenated flame retardant polyolefin compound to the extruder.

15. The non-halogenated flame retardant polyolefin tape manufacturing system of claim 9, further comprising:

an orienting and annealing assembly, disposed between the cutting assembly and the winding assembly, that orients and anneals the feeds of non-halogenated flame retardant polyolefin material in a lengthwise direction to orient molecules within the non-halogenated flame retardant polyolefin material such that tensile strength of the feeds is greater in the lengthwise direction than in a widthwise direction.

16. A method for making a cable, the method comprising the step of:

providing a set of conductors;

providing non-halogenated flame retardant polyolefin tape;

wrapping the non-halogenated flame retardant polyolefin tape around the set of conductors; and

extruding a jacket around the wrapped set of conductors to form the cable.

17. The method of claim 16 wherein the step of providing the non-halogenated flame retardant polyolefin tape includes the steps of:

extruding molten non-halogenated flame retardant polyolefin material through a die that defines an elongated opening;

cooling the extruded non-halogenated flame retardant polyolefin material so that the extruded non-halogenated flame retardant polyolefin material hardens into a contiguous sheet of non-halogenated flame retardant polyolefin material; and

cutting the contiguous sheet of non-halogenated flame retardant polyolefin material lengthwise to form multiple parallel feeds of non-halogenated flame retardant polyolefin tape.

18. A cable, comprising:

a set of conductors;

non-halogenated flame retardant polyolefin tape wrapped around the set of conductors; and

a jacket extruded around the wrapped set of conductors.

19. The cable of claim 18 wherein the non-halogenated flame retardant polyolefin tape is made by a method comprising the steps of:

extruding molten non-halogenated flame retardant polyolefin material through a die that defines an elongated opening;

cooling the extruded non-halogenated flame retardant polyolefin material so that the extruded non-halogenated flame retardant polyolefin material hardens into a contiguous sheet of non-halogenated flame retardant polyolefin material;

cutting the contiguous sheet of non-halogenated flame retardant polyolefin material lengthwise to form multiple parallel feeds of non-halogenated flame retardant polyolefin tape; and

simultaneously winding each of the multiple parallel feeds on a respective core.

20. A cable manufacturing system for making a cable, comprising:

a conductor source that provides a set of conductors;

an non-halogenated flame retardant polyolefin tape source that provides non-halogenated flame retardant polyolefin tape;

a feed assembly that wraps the non-halogenated flame retardant polyolefin tape around the set of conductors; and

an extruding assembly that extrudes a jacket around the wrapped set of conductors to form the cable.

21. The cable manufacturing system of claim 20 wherein the non-halogenated flame retardant polyolefin tape source includes:

an extruder having a die that defines an elongated opening, the extruder providing molten non-halogenated flame retardant polyolefin material through the die;

a cooling assembly, coupled to the extruder, that receives the extruded non-halogenated flame retardant polyolefin material from the extruder and cools the extruded non-halogenated flame retardant polyolefin material so that the extruded non-halogenated flame retardant polyolefin material hardens into a contiguous sheet of non-halogenated flame retardant polyolefin material; and

a cutting assembly that receives the contiguous sheet of non-halogenated flame retardant polyolefin material and cuts the contiguous sheet of non-halogenated flame retardant polyolefin material lengthwise to form multiple parallel feeds of non-halogenated flame retardant polyolefin tape.