WO2002020898A2

WO2002020898A2 - Die for making composite cable

Info

Publication number: WO2002020898A2
Application number: PCT/US2001/026047
Authority: WO
Inventors: Hong Peng
Original assignee: Owens Corning
Priority date: 2000-08-30
Filing date: 2001-08-21
Publication date: 2002-03-14
Also published as: AU8657201A; WO2002020898A3

Abstract

The shortcomings of the prior art are overcome by the disclosed die (100) that impregnates a group of strands (16) and wirecoats the impregnated strands to form a composite cable (30). The shortcomings are also overcome by the disclosed method of manufacturing a composite cable using the die. The die includes a body (105) with a center channel (110) and an outer channel (112). A thermoplastic resin (120) is supplied to the die to impregnate and wirecoat the strands. As the strands are attenuated through the center channel, the strands are impregnates with resin. As the impregnates strands are attenuated through the outer channel, they are wirecoated with more resin. The die includes a bushing (190) through which a composite cable is attenuated. The die includes a wall (118) which separates the center channel and the outer channel. The wall includes ports (114, 116) through which the resin flows from the outer channel to the center channel. The melt pressure in the center channel can be adjusted by varying the size and number of the ports. The melt pressure in the outer channel may be adjusted as well. A gasket (184) is provided between the wall and the body. The thickness of the gasket can be varied to adjust how far the wall is inserted. The die also includes an inlet plate (170) with several apertures (176). The strands pass through the apertures and into the center channel. The inlet plate separates the strands as they enter the die. The spacing between the strands facilitates the impregnation of the strands. The composite cable attenuated from the die is subsequently cooled to harden the resin. The cable is wound on a spool for later use.

Description

DIE FOR MAKING COMPOSITE CABLE

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION This invention generally relates to the manufacture of a composite cable with multiple strands, and in particular, to a die for the manufacture of a composite cable. This invention also relates to a method of manufacturing a composite cable by impregnating continuous strands and wirecoating the impregnated strands. The invention is particularly useful in the production of a composite cable for use as a reinforcement or support member.

BACKGROUND OF THE INVENTION

A cable is typically used as a support element for reinforcement in construction, housing, and other similar environments. The cable may be a steel braided cable or synthetic composite cable. Composite cables are easier and more economical to manufacture than steel braided cables. Composite cables can also provide better performance than steel braided cables.

A composite cable that is used as a support element must accommodate both tensile stresses and compressive stresses, without excessive extension or compression of the cable.

A composite cable typically includes one or more reinforcement strands, such as 2200 tex glass fibers. The glass fibers are surrounded or wirecoated with a resinous material, such as polyvinyl chloride (PVC) resin, that forms a protective jacket.

In some composite cables, strands are impregnated with a resin and formed into a single cable. The impregnated strands are subsequently wirecoated by another apparatus. Resin impregnation between individual strands in a composite cable increases the load bearing capability of the cable and the transfer of loads among the strands. The tensile strength of a cable without impregnated strands is significantly less than a cable with impregnation. In the present invention, an objective of the resin impregnation is to impregnate between the strands. A secondary objective of the resin impregnation is to penetrate inside of the strands. The penetration of the strands depends on the viscosity of the resin and could be minimal. The distance that resin penetrates or impregnates a bundle of strands is a function of several variables. Some of the variables include: the permeability coefficient of the media, the melt pressure of the resin in the die, the amount of time that the strands are in contact with the resin in the die, and the viscosity of the resin. The distance that the resin penetrates the strands increases if the permeability coefficient, melt pressure, or the amount of time under pressure increases. An increase in the viscosity of the resin generally results in a decrease in penetration.

Wirecoating processes are typically conducted at a high line speed. Since the strands are subject to the resin for a short period of time, the penetration of the resin into the strands decreases. The viscosity of a thermoplastic resin is relatively high. As a result, the resin penetration into the strands is difficult. For a multi-filament strand, as the resin pressure increases, the porosity or permeability of the strand may decrease. Therefore, the resin penetration into the strand does not improve by simply increasing the pressure of the resin inside the die. Composite cables are manufactured by systems that include separate impregnating and wirecoating devices. An example of such a cable manufacturing system is disclosed in U.S. Pat. No. 4,956,039 to Olesen et al. (Olesen). Olesen discloses a system for and method of manufacturing a composite cable. The manufacturing system includes an impregnation device 18, first and second extruders 19, 22, and a cooling apparatus 20. Bundles 15' are attenuated through the impregnation device 18 which impregnates the bundles 15' with a hot melt adhesive. The first extruder 19 applies a sleeve of thermoplastic material filled with short reinforcement elements on the core string 11'. The second extruder 22 applies another layer of thermoplastic material. The system of Olesen is not very economical because it utilizes multiple devices to perform the impregnating and wirecoating functions.

Another system for manufacturing a composite cable is disclosed in U.S. Pat. No. 5,451,355 to Boissonnat et al. (Boissonnat). Boissonnat discloses a high pressure die that applies a high and uniform melt pressure to force molten resin to penetrate inside of a composite thread. However, for the reasons discussed above relating to resin impregnation, the penetration of the resin into the thread is minimum.

A need exists for an economical way to manufacture a strong composite cable with multiple strands. Also, a need exists for an economical way to facilitate the impregnation of the strands. Similarly, a need exists for a single die that impregnates reinforcement threads and wirecoats the impregnated strands.

SUMMARY OF THE INVENTION The shortcomings of the prior art are overcome by the disclosed die that impregnates a group of strands and wirecoats the impregnated strands to form a composite cable. The shortcomings are also overcome by the disclosed method of manufacturing a composite cable using the die.

The die includes a body with a center channel and an outer channel. A thermoplastic resin is supplied to the die to impregnate and wirecoat the strands. The resin enters the center channel and outer channel. As the strands are attenuated through the center channel, the strands are impregnated with resin. As the impregnated strands are attenuated through the outer channel, they are wirecoated with more resin. The die includes a bushing through which a composite cable is attenuated. The die includes a removable wall, which separates the center channel and the outer channel. The wall includes ports through which the resin flows from the outer channel to the center channel. The melt pressure in the center channel can be adjusted by varying the size and number of the ports.

The melt pressure in the outer channel can be similarly adjusted. The depth at which the wall is inserted into the die may be adjusted to vary the cross-sectional area of the outer channel. The area of the outer channel affects the melt pressure in the channel.

A gasket is positioned between the wall and the body. The thickness of the gasket can be varied to adjust how far the wall is inserted into the die.

The die also includes an inlet plate with several apertures. The strands pass through the apertures and into the center channel. The inlet plate separates the strands as they enter the die. The spacing between the strands facilitates the impregnation of the strands.

The composite cable attenuated from the die is subsequently cooled to harden the resin. The cable is wound on a spool for later use.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a front view of a composite cable forming system embodying the principles of the invention; Fig. 2 is apian view of the system of Fig. 1;

Fig. 3 is a cross-sectional schematic view of a die embodying the principles of the invention;

Fig. 4 is a cross-sectional view of the die of Fig. 2 taken along the lines "4-4"; Fig. 5 is a bottom view of a nozzle embodying the principles of the invention;

Fig. 6 is a cross-sectional view of the nozzle of Fig. 5 taken along the lines "6-6";

Fig. 7 is an end view of an inlet plate embodying the principles of the invention;

Fig. 8 is a cross-sectional view of the inlet plate of Fig. 7 taken along the lines "8- 8"; and Fig. 9 is a cross-sectional view of a composite cable embodying the principles of the invention.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION A composite cable may include one or more reinforcement strands coated with a thermoplastic resin material. The terms "strand," "thread," and "wire" are used interchangeably to designate a continuous element comprising multiple filaments. The present invention relates to a die for manufacturing a composite cable by impregnating continuous strands with resin and wirecoating the impregnated strands. A composite cable forming system is illustrated in Figs. 1 and 2. The cable forming system 5 includes a strand supply 10 and a resin supply 20. The strand supply 10 and the resin supply 20 are directed to a die 100, which combines them to form a composite cable. The continuous cable 30 is attenuated from the die 100.

The strand supply 10 includes several packages 14 of continuous strand 16. The supply 10 includes a creel 12 for supporting the packages upstream of the die 100 and a strand guide 18 for guiding strand from packages 14 to the die 100.

Any number of packages may be used, but it is generally preferred that the number of packages is in the range of six to ten, and in the preferred embodiment described below, the number is seven. A strand 16 from each of the packages 14 is thread through the guide eye 18 to the die 100.

The resin supply 20 is coupled to the die 100 to provide molten resin thereto. The resin supply 20 includes a resin hopper 22 and an extruder 24. Resin is introduced into the hopper 22 in the form of individual resin pellets. The pellets are transformed into a molten resin flow by the extruder 24. The molten flow is supplied to the die 100 to be utilized with the strands.

The composite cable 30 is attenuated downstream of the die 100. The attenuation force on the cable continuously draws strands 16 from the packages 14 and into the die 100.

Some composite cables are made with impregnated strands. During the impregnation process in the die, a thin film of molten resin, such as polyvinyl chloride (PVC) resin, is directed between individual strands to maintain space between them.

Resin impregnation between individual strands in a composite cable increases the load bearing capability of the cable and the transfer of loads among the strands. The tensile strength of a cable without impregnated strands is significantly less than a cable with impregnation.

As discussed above, the distance that resin penetrates a bundle of strands is a function of several variables. Some of the variables include: the permeability coefficient of the media, the melt pressure of the resin in the die, the amount of time that the strands are in contact with the resin in the die, and the viscosity of the resin. The distance that the resin penetrates the strands increases if the permeability coefficient, melt pressure, or the amount of time under pressure increases. An increase in the viscosity of the resin generally results in a decrease in penetration. Since some strands are subject to the resin for a short period of time, the penetration of the resin into those strands decreases. When a thermoplastic resin is used, its viscosity is relatively high, and the resin penetration into the strands is difficult. For a multi-filament strand, as the resin pressure increases, the porosity or permeability of the strand may decrease. Therefore, the resin penetration into the strand does not improve by simply increasing the pressure of the resin inside the die.

In the present invention, the strands are separated prior to impregnation to facilitate the application of resin between the strands. By separating the strands, the resin flows between the strands as they pass through the die.

The length of time that the strands are subject to the resin is also a factor in the resin penetration. In the present invention, the length of the impregnation channel in the die is longer than that in conventional dies. The longer channel increases the amount of time that the strands are resident in the die and therefore in contact with the resin under pressure in the die. The increase in residence time improves impregnation of the strands. The impregnation of the strands improves the load bearing capacity of the cable and the load transferring among the strands in the cable. The melt pressure of the resin is adjusted to increase the efficiency of resin impregnation. If the melt pressure is too high, the resin flow tends to press all of the strands in the radial direction toward the center line of the die and perpendicular to their path of movement. If the strands are pressed toward each other, the spacing between the strands is closed, which reduces the ability of the resin to impregnate the strands. The result is a lower efficiency of resin impregnation between the strands.

Accordingly, the melt pressure of the resin for impregnation is preferably adjustable since operation conditions may change for different cable manufacturing processes. Some examples of operation conditions include: the number of strands in the cable, the speed at which the strands are attenuated through the die, the length of the die, the type of resin, etc. By adjusting the melt pressure, the optimal resin impregnation efficiency can be enhanced for the manufacture of different composite cables. The application of a sheath of resin on the impregnated strands is referred to as wirecoating. Wirecoating improves the surface finish of the cable and protects the impregnated strands. The melt pressure of the resin for wirecoating also affects the final composite cable product. The melt pressure is preferably adjustable as well to allow for changes in operation conditions. With these general principles identified, selected implementations of these principles in currently preferred embodiments are set forth below.

A die for a cable forming system embodying the principles of the invention is illustrated in Figs. 3-9. A cross-sectional schematic view of a die illustrating the concepts of the invention is shown in Fig. 3. The die 100 includes a body 105 with a center channel 110 and an outer channel

112. The channels 110, 112 intersect at a downstream end of the die 100. The strands 16 are attenuated through a strand inlet and into the center channel 110, in the direction of arrow "A." The inlet of the center channel 110 is greater than the outlet of the channel 100. In the preferred embodiment, the die 100 includes an inner wall 118 which is positioned between the center channel 110 and the outer channel 112. The wall is moveable relative to the die 100 to enable replacement and/or adjustment of the wall for reasons discussed below. The wall 118 includes ports which enable fluidic communication between the channels 110, 112. Ports 114, 116 are located at opposite positions along the circumference of the wall 118. Any number of ports may be used, but it is generally preferred that the wall includes two ports. Also, the ports may be located anywhere along the circumference of the wall, preferably, equally spaced about the circumference.

The die 100 receives a resin supply 120 from the extruder 24. The resin supply 120 enters a resin inlet and is split into flows 122, 124 which are directed through the outer channel 112 and center channel 110, respectively. As shown in Fig. 3, once resin flow 122 passes through the ports 114, 116, it splits into flows 126 and 128. Flow 126 is in the direction opposite to the advancement of the strands 16. The resin in flow 126 preheats and initially wets the strands 16. Flow 128 is in the direction of the strand movement. The resin in flow 128 impregnates the strands and forms the core section of the cable. The impregnated strands are subsequently wirecoated with resin from the outer channel 112 as the impregnated strands pass through the exit region of the outer channel 112.

An exemplary embodiment of a die embodying the principles of the invention is now described with reference to Fig. 4.

The die 100 includes a body 105, which, in the preferred embodiment includes two portions that are coupled together by fasteners such as screws. The body 105 has an internal cavity or passage 107 that includes a center channel 110 and an outer channel 112. Cavity 107 includes an inner surface and an outlet. In the illustrated embodiment, the body 105 includes a hollow partition or nozzle 150, which separates the channels 110, 112. The nozzle 150 is disposed concentrically within the cavity 107 of the die.

The nozzle 150 includes ports 156, 158, which provide fluidic communication between the outer channel 112 and the center channel 110. In the illustrated embodiment, the ports are circular. However, the ports may have any shape that permits the flow of resin therethrough. Also, the ports preferably have a diameter of approximately 0.125 in. (0.3 cm). As discussed above, the number and location of the ports may be adjusted based on the particular manufacturing conditions for the cable. The center channel 110 is defined by an inner surface 152 of the nozzle 150. The center channel 110 is substantially cylindrical and has a tapered exit portion. The outer surface 154 of the nozzle 150 has a diameter that is slightly less than the diameter of the cavity 107. The annular space between the nozzle outer surface 154 and the cavity 107 defines the outer channel 112.

The die 100 includes a system for supplying resin from the extruder to the center and outer channels. The system includes a flow chamber 130 and a flow port 132. The flow chamber 130 is in fluidic communication with the exit of the extruder 24 and the flow port 132. Similarly, the flow port 132 is in fluidic communication with cavity 107.

Accordingly, the resin supply 120 flows from the extruder 24 through the flow chamber

130 and flow port 132 and into the cavity 107.

In the illustrated embodiment, the longitudinal axis of the cavity 107 is oriented perpendicularly to the longitudinal axes of the flow chamber 130 and the flow port 132.

However, the artisan will appreciate that the cavity 107, flow chamber 130, and flow port

132 can be oriented in a variety of arrangements.

The die 100 includes a resin flow adjuster by which the flow of resin in the die may be controlled. The resin flow adjuster 140 controls the flow of resin through the flow port 132. In the illustrated embodiment, the resin flow adjuster 140 includes a cavity 142 formed in the die 100 and an adjustment screw 144 mounted in the cavity 142. The cavity

142 intersects the flow port 132, and preferably, extends through the flow port 132 as shown in Fig. 4.

The flow port 132 is threaded to receive the adjustment screw 144. The adjustment screw 144 is rotatably mounted in the cavity 142. The cavity 142 is oriented to enable the screw 144 to restrict a portion or all of the cross-sectional area of the flow port 132. By varying the amount that the screw 144 extends into the flow port 132, the resin flow through the flow port 132 is controlled.

Returning to the description of the nozzle, an exemplary embodiment of the nozzle is shown in Figs. 4-6. As described above, the nozzle 150 includes an inner surface 152 and an outer surface 154. The inner surface 152 defines the central channel 110 for impregnation of strands and the outer surface 154 defines the outer channel 112 for the wirecoating of the strands. The nozzle 150 includes ports 156, 158 that extend from the inner surface 152 to the outer surface 154. The nozzle 150 is disposed concentrically in the cavity 107 of the die 100. The cavity 107 includes a substantially cylindrical portion and a tapered portion. The tapered portion directs the resin in the outer channel 112 toward the impregnated strands. In the illustrated embodiment, the nozzle 150 includes a first end with a conical tip 162 that has a slope substantially similar to that of the cavity tapered position.

The nozzle 150 also includes a flange 160 at one end. The diameter of the flange 160 is larger than the diameter of the cavity 107. Accordingly, the flange 160 engages in a seat 134 formed in the body 105. The extent to wliich the nozzle 150 is inserted into the cavity 107 is limited by the seat 134.

As understood by the skilled artisan, the flow of resin into the center channel and along the outer channel is influenced by the melt pressure in each of the channels. The impregnation and wirecoating processes are affected by the flow of resin in the respective channels. As previously discussed, the melt pressures are controlled to enhance the efficiency of the resin impregnating and wirecoating processes.

The melt pressure in the center channel 110 can be adjusted several ways. First, the size of the ports 156, 158 in the nozzle can be changed. If the diameter or other dimension of the ports increases, the pressure drop in the flow through the ports decreases, thereby resulting in more resin and a higher melt pressure in the center channel 110. Second, the number of ports in the nozzle can change. If the number of ports increases, the overall flow through the ports increases. The result is that the melt pressure in the center channel 110 also increases.

In the illustrated embodiment, the melt pressure in the center channel 110 is in the range of approximately 150 to 500 psi (1034 to 3447 kPa). If the melt pressure is higher than 500 psi (3447 kPa), the resin flow tends to press all the strands in the radial direction toward the centerline of the cavity 107. The resulting composite cable has a lower resin impregnation efficiency between the strands and less reinforcement strength.

The melt pressure in the outer channel 112 can also be adjusted. The melt pressure may be changed by varying the cross-sectional area of the outer channel. In the illustrated embodiment, such a variation is achieved by setting the axial position of the nozzle 150 in the cavity 107. The axial position is set by a gasket 184, which is positioned between the nozzle flange 160 and the seat 134.

The cross-sectional area of the outer channel 112 is determined by the thickness of the gasket 184. For example, if the thickness of the gasket 184 is increased, the nozzle

150 does not extend as far into the die 100 as it would if the gasket 184 was thinner. Since the depth of the nozzle 150 is shallower, the distance between the outer surface 154 of the nozzle 150 and the cavity wall increases near the conical tip and tapered portion. Such an increase in area reduces the restriction on the resin flow 122, thereby allowing additional resin to flow through the outer channel 112 and wirecoat the impregnated strands.

The nozzle 150 includes an exit port 164 through which the impregnated strands are attenuated. The diameter of the exit port 164 is slightly smaller than the diameter of the finished composite cable 30. The difference in diameters allows the resin to be added during the wirecoating process. As the impregnated strands leave exit port 164, the resin in the outer channel 112 wirecoats the strands.

The nozzle 150 is shown in greater detail in Figs. 5 and 6. In the illustrated embodiment, the nozzle 150 includes a flow guide 166. The flow guide 166 has an outer diameter substantially equal to the diameter of the cavity 107. The flow guide 166 includes tapered portions 168 that direct the resin flow 122 in the outer channel 112 toward port 158 and the outlet of the die 100. The nozzle flange 160 includes a hole 169 to secure the nozzle 150 to the die 100 as appreciated by the artisan.

The die 100 is preferably made from stainless steel or other corrosion and temperature resistant material. The gasket is preferably made from a high temperature resistant steel.

The die 100 includes a bushing as shown in Fig. 4. In the illustrated embodiment, the bushing 190 is removably coupled to the body 105 proximate to the outlet of the body 105. The bushing 190 is positioned proximate to the outlet of the die 100. The bushing 190 includes an exit port 192 through which the wirecoated cable is attenuated. The diameter of the exit port 192 is selected based on the desired outer diameter of the composite cable. Preferably, the inner diameter of the exit port 192 is substantially equal to the desired outer diameter of the composite cable 30.

The bushing 190 includes an inner tapered surface 194. As the impregnated strands pass through the exit region of the outer channel 112, the resin flowing through the outer channel 112 coats the impregnated strands as appreciated by the skilled artisan.

In the illustrated embodiment, the slope of the tapered surface of the cavity 107 is similar to the slope of the bushing tapered surface 194. It is to be understood that it is not necessary that the tapered surfaces have the same slope. Similarly, preferably the conical tip 162 of the nozzle 150 has substantially the same slope as the tapered surfaces.

The removable bushing serves multiple functions. First, the bushing 190 is easily replaced when it is worn. Second, since the diameter of the composite cable 30 is determined by the inner diameter of the bushing exit port 192, a bushing can be replaced with another bushing with a different exit port diameter to achieve a different sized composite cable.

Preferably, the bushing is made of a corrosion resistant steel, such as a steel that includes more than 12% chromium or nickel alloy. However, the bushing can be made of tool steel with a wear resistant coating, such as a hard chrome plating, a nickel coating, or a titanium carbide coating.

In a preferred embodiment, the die 100 includes an inlet plate or guide for controlling the movement of the strands into the die. An exemplary inlet plate embodying the principles of the invention is shown in Figs. 4 and 7-8. The inlet plate 170 separates the strands 16 as they enter the die 100. The inlet plate 170 guides the strands 16 so they are spaced apart, and in particular, spaced at a distance greater than the spacing in a finished composite cable. By spacing the strands 16 apart during the impregnation process, the efficiency of the impregnation of the strands increases. The increase in impregnation of strands in a composite cable increases the load transfer among the strands in the cable and the load bearing capability of the cable, as previously discussed.

The inlet plate 170 includes a flange 172 and an extension 174. The inlet plate 170 is coupled to the inlet region of the nozzle 150. The flange 172 engages the end of the nozzle 150 and limits the distance that the extension 174 protrudes into the interior nozzle 150. The inlet plate 170 includes several apertures 176 as shown in Fig. 7. The strands

16 are attenuated through the apertures 176 and into the center channel 110. The apertures 176 may be beveled to reduce damage to the glass strands. The inlet plate 170 preferably has the same number and arrangement of apertures 176 as the number and arrangement of the strands 16 in the finished composite cable. One aperture is centrally located on the inlet plate 170 and the other apertures are circumferentially and evenly spaced around the central aperture. In the illustrated embodiment, the circled formed by the circumferentially spaced apertures is concentric with the nozzle 150 and preferably has a larger diameter than the exit port 164 of the nozzle 150. The amount of separation between the strands 16 is determined by the distance between the apertures 176 on the inlet plate 170. The strands 16 advance along lines nearly parallel to the center axis of the die cavity 107 with an angle of approximately 1° to 2°, pitched toward the central axis at the exit of the nozzle 150. The paths of travel are determined by the locations of the apertures 176 on the inlet plate 170.

In the illustrated embodiment, the die 100 also includes heating strips to maintain the resin in the die in a molten state. The heating strips 180, 182 are secured to the external surfaces of the die 100 shown in Fig. 4. The heating strips are preferably electrical resistance heaters which heat the die to an operating temperature of approximately 300°F - 350°F (180°C to 190°C). The die operating temperature depends on the melting point of the particular resinous material. One or more thermocouples (not shown) may be utilized to monitor and regulate the temperature of the die as appreciated by the artisan.

Now the operation of the composite cable forming system is described. Initially, the desired number of packages 14 are mounted on a creel 12.

A strand 16 from each package 14 is threaded through the strand guide 18. Once the die 100 is assembled, the strands 16 are thread through the apertures 176 in the inlet plate 170, which is not yet coupled to the die. Each strand 16 is subsequently pulled through the nozzle 150 with a hook (not shown). The inlet plate 170 is coupled and secured to the die 100 to prevent molten resin from exiting the center channel 110.

Resin is supplied from the extruder 24 to the die 100. The resin flows from the extruder 24 into the flow chamber 130, through the flow port 132, and into cavity 107. The resin flow 120 splits into two flows 122, 124. Flow 124 enters ports 156, 158 on the nozzle 150 and flows into the center channel 110. Flow 122 continues along the outer surface 154 of the nozzle 150 in the outer channel 112. Flow 122 is directed by the tapered surfaces 168 of the flow guide 166 along the outer nozzle surface 154.

As the strands 16 are attenuated through the center channel 110, resin impregnates the strands 16. The impregnated strands exit channel 110 and the resin flow in the outer channel 112 wirecoats the impregnated strands and forms a smooth outer surface.

The composite cable 30 is be attenuated from the die 100 by any mechanism that can continuous pull the cable, such as a pair of rollers. In the illustrated embodiment, a cooling apparatus, such as a cooling bath, is positioned between the die 100 and the attenuating mechanism. As the cable is attenuated from the die, it passes through the cooling apparatus to cool and harden the resin in the composite cable 30. hi operation, the strands 16 are drawn through the die 100 at a line speed generally in the range of approximately 10 to 200 in/sec ( 25 to 500 cm/sec), and preferably in the range of approximately 20 to 60 in/sec ( 50 to 150 cm/sec). The time that the strands 16 are resident in the die 100 ranges from approximately 0.02 to 0.5 seconds.

A cross-sectional view of a composite cable formed with a die embodying the principles of the invention is shown in Fig. 9. The strands 16 are surrounded by resin 32. Strands are usually positioned symmetrically about the center strand in the composite cable. However, it is not necessary that the strands in the cable be symmetrical about the center strand.

Replacement packages 14 may be loaded on the creel 12 during the manufacturing process. A method of introducing a new strand into the die is by splicing the trailing end of an original package to the leading end of a new package. Shreds of resin are used to splice the strand ends, thereby not introducing foreign materials into the composite cable. In either mode, the replacement of packages and strands is accomplished without any interruption in the manufacturing process.

It is to be understood that the artisan will appreciate how to manufacture the die. For example, the channels, ports, and cavities in the die may be bored by any appropriate tool.

The reinforcement fibers suitable for use in the present invention may be selected from a wide variety of materials. The preferred material for the fiber is a glass fiber continuous strand roving. The preferred glass fibers are 300 to 10,000 tex glass fibers, and more particularly, 1,200 to 4,800 tex glass fibers.

Some examples of suitable thermoplastic resins useful for forming the composite cable are polyvinyl chloride (PVC), low and high density polyethylene (LDPE, HDPE), and polypropylene (PP).

The artisan will also appreciate that there are many possible variations on the particular embodiments described above that would be consistent with the principles of the invention.

The cable forming system may include several dies in parallel to form several cables simultaneously. Alternatively, a die may include a plurality of inlet plates and channels to form several cables simultaneously. The resin flow adjuster is not limited to the arrangement of an adjustment screw in a cavity. Any type of flow adjuster may be employed. For example, a variable orifice, damper or check- valve may be used. The number of apertures in the inlet plate may vary depending on the number of reinforcement strands desired in a particular composite cable.

The number of strands in a composite cable may vary depending on the desired physical characteristics of the cable.

The die may be formed from multiple parts that are coupled together by any fastening mechanisms. Alternatively, the die may be a unitary piece construction.

The geometry of the removable wall in the die may be varied to achieve a particular flow pattern or melt pressure in the die.

The composite cable may be a flat rectangular ribbon instead of a round cable.

Claims

WHAT IS CLAIMED IS:

1. A die (100) for manufacturing a cable (30) from a plurality of continuous strands (16) comprising: a body (105) having a passage (107) therethrough, said passage having an inner surface and having an outlet; a hollow partition (150) disposed in said passage, said partition having an outer surface (154) defining with said inner surface of said passage an annular outer channel (112) and having an inner surface defining an inner channel (110) , said partition further including ports (156, 158) fiuidically coupling said inner and outer channels, wherein said partition includes a first end at which said inner and outer channels intersect, whereby molten resinous material (120) introduced into said outer channel flows into said inner channel through said port to impregnate strands passing through said inner channel and wirecoats the impregnated strands as they emerge from the first end, and the wirecoated impregnated strands emerge from said outlet.

2. The die of claim 1, wherein said partition (150) is adjustably positionable in said passage (107) to define an adjustable restriction to control the flow of resinous material (120) in said body (105).

3. The die of claim 2, wherein a portion of said partition (150) and said body inner surface proximate said first end are tapered so that axial displacement of said partition changes the annular cross-section of said outer channel (112).

4. The die of claim 1, wherein said inner channel (110) includes an inlet and an outlet, and said inlet has a greater cross-sectional area than said outlet.

5. The die of claim 1 , further comprising: a guide (170) having a plurality of apertures (176) defining a spacing between strands (16) conducted through said apertures, said spacing being greater than the spacing between strands at said outlet.

6. The die of claim 1, wherein said body (150) includes defining said outlet.

7. A cable (30) manufactured by the die of claim 1.

8. A die (100) for manufacturing a cable (30) from a plurality of continuous strands (16) comprising: a body (105) including: an strand inlet; a resinous material inlet; an impregnation zone (110) disposed downstream of said strand inlet; a wirecoating zone (112) downstream of said impregnation zone; and resin passages (124) coupling said impregnation zone with said resinous material inlet and said wirecoating zone with said resinous material inlet, wherein a resinous material (120) supplied to said resinous material inlet flows to said impregnation zone and said wirecoating zone through said resin passages, to impregnate the strands with the resinous material in said impregnation zone and to wirecoat the impregnated strands with the resinous material in said wirecoating zone.

9. The die of claim 8, further comprising: a flow restriction to control the flow of resinous material (120) through said resinous material inlet.

10. The die of claim 9, further comprising: a flow restriction to control the flow of resinous material (120) to said impregnation zone (110) and said wirecoating zone (112).

11. The die of claim 8, further comprising: a guide (170) disposed adjacent to said strand inlet and having a plurality of apertures (176) defining a spacing between strands (16) conducted through said apertures into said strand inlet.

12. The die of claim 8, further comprising: a hollow partition (150), said partition having an inner surface (118) defining said impregnation zone (110), whereby resmous material (120) introduced into said impregnation zone impregnates strands passing through said impregnation zone.

13. The die of claim 12, wherein said body (105) has an internal passage (107) with an inner surface, said partition (150) having an outer surface (154) defining with said inner surface of said internal passage an annular outer channel (112), whereby resinous material (120) introduced into said wirecoating zone wirecoats impregnated strands passing through said wirecoating zone.

14. The die of claim 8, wherein said resin passages (124) include a port (114, 116) defined in said partition (150), said port fiuidically coupling said inner (110) and outer (112) channels, and resinous material (120) flows from said outer channel through said port and into said impregnation zone.

15. A method of manufacturing a cable (30) from a plurality of continuous strands (16), the method comprising the steps of: attenuating strands through a body (105); introducing molten resinous material (120) into said body; conducting the resinous material to an impregnation zone (110) in said body; impregnating the strands with the resinous material in the impregnation zone; conducting the resinous material to a wirecoating zone (112) in said body; wirecoating the impregnated strands with a resinous material in the wirecoating zone; and attenuating the impregnated and wirecoated strands from an outlet of the body.

16. The method of claim 15, wherein said body (105) includes a cavity (107) and a partition (150) disposed in the body cavity, the partition defines the impregnation zone (110), and said step of conducting the resinous material (120) to an impregnation zone includes conducting the resinous material resin through a resin passage (124) in said body and a port (114, 116) in the partition.

17. The method of claim 16, wherein said step of conducting resin (120) to a wirecoating zone (112) includes conducting the resinous material through a resin passage (122) along the partition (150).

18. The method of claim 17, wherein said step of conducting the resinous material (120) to a wirecoating zone (112) includes controlling the flow of resin by adjusting the position of the partition (150) in the body cavity (107).

19. The method of claim 15, wherein said steps of conducting the resinous material (120) to an impregnation zone (110) and to a wirecoating zone (112) occur simultaneously.

20. The method of claim 15, wherein said step of attenuating strands (16) through a body (105) includes spacing the strands as they enter said body a distance greater than the distance at which the strands are spaced as they leave the body.