Bryant, David (1145 Sailing Way, Laguna Beach, CA, 92651, US)
CORRUGATED COMPOSITE POLE [1] In relation to this United States Utility Application, Applicants claim priority to earlier US Provisional Application Serial No. 60/590,080, filed on July 21, 2004, the contents of which is incorporated by reference herein. Background of the Invention [2] Present utility poles are generally made of wood, steel or concrete, each of which suffer from inherent problems. Initial costs for wood poles are relatively low, however, these low initial costs are far outweighed by long-term problems including the re¬ quirement for extensive maintenance and routine replacement. For example, wood poles are directly susceptible to rot, bug infestation and/or animal attack and de¬ struction due to weather. Moreover, environmentally questionable treatment of poles with creosote or pentachlorophenol have given rise to questions of environmental safety and appropriate disposal. Existing alternatives include tubular light duty steel poles and concrete poles. Although such poles provide equivalent alternatives to wood, they each have problems regarding weight, shipping constraints, costs and corrosion. [3] Fiber-reinforced composites have been suggested as an alternative. However, such poles have been shown to suffer from compressive strains, deflective forces and buckling. Under current composite pole designs, further strengthening of pole sections have the effect of added weight and cost to the poles which further effects shipment and construction of the poles. Moreover, due to these inherent difficulties, such previously disclosed composite poles are limited in height. [4] Accordingly, a need exists for a composite pole capable of reaching extended heights while maintaining minimal weight and material costs in addition to maintaining superior strength. Summary of the Invention [5] The present invention discloses a composite pole designed to enable formation of pole structures having extended heights and superior strength characteristics. In one embodiment, the pole comprises one or more panel sections that mate to form a unitary pole structure. Each of the one or more panel sections further comprise an outer skin that forms an outer periphery, an inner skin that forms an inner periphery and a corrugated middle composite that couples the outer skin to the inner skin, wherein the outer skin, the inner skin and the corrugated middle composite comprise a fibrous material and resin. [6] In another embodiment, a composite pole is disclosed having one or more panels comprising a fibrous material embedded in a resin. In this embodiment, each panel consists of an outer skin that forms an outer periphery coupled to an inner skin that forms an inner periphery by a corrugated middle composite. Each panel further comprises a first side edge having a first coupling device and a second side edge having a second coupling device, the first and second coupling devices for mating panel sections. [7] In another embodiment, a composite pole is disclosed comprising one or more panel sections, each of the one or more panel sections comprising an outer skin forming an outer periphery, an inner skin forming an inner periphery and a plurality of longitudinally extending composite tubes spanning the area between the inner and outer skins, wherein the outer skin, the inner skin and the composite tubes comprise a fibrous material and resin. [8] In yet another embodiment, a method is disclosed to pultrude a composite pole of the type described herein. The method comprises the steps of providing a first fibrous material for an outer skin; providing a second fibrous material for an inner skin; providing a third fibrous material for a corrugated middle composite; wetting out, with resin, the first fibrous material, the second fibrous material, and the third fibrous material; placing the wetted-out second fibrous material around an inner mandrel; in¬ terweaving the wetted-out third fibrous material around a plurality of corrugated mandrels; placing the interwoven third fibrous material around the second fibrous material; placing the wetted-out first fibrous material around the interwoven third fibrous material; pulling the wetted-out fibrous materials through a heated die and over the mandrels to cure the resin; and milling the cured composite pole to a predetermined length. Brief Description of the Drawings [9] The embodiments and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, wherein: [10] FIG. 1 illustrates a cross sectional view of a composite pole comprising an outer skin coupled to an inner skin by a corrugated middle composite. [11] FIG. 2 illustrates a cross sectional view of two panels and associated coupling devices for forming a composite pole. [12] FIG. 3 illustrates a cross sectional view of a panel that can be mated to other panels to form a composite pole. [13] FIG. 4 illustrates a cross sectional view of a mandrel design that may be used to form panels in a pultrusion process. [14] FIG. 5A illustrates a cross sectional view of a composite pole comprising an outer skin coupled to an inner skin by a plurality of middle composite cross brace sections. [15] FIG. 5B illustrates a cross sectional view of a panel and associated coupling devices for forming a composite pole. [16] FIG. 6 illustrates a cross sectional view of a composite pole comprising an outer skin, an inner skin and a plurality of longitudinally extending composite tubes. Detailed Description of the Invention [17] The present invention relates to multidimensional composite poles having the strength and weight properties that enable poles of extended height while minimizing costs. In accordance with the invention, the cross sectional design of the pole provides for reinforcement of the walls of the pole without added weight and bulk. [18] Composite poles have been disclosed previously, however, none of these previously disclosed poles have provided a viable solution to wood, concrete or steel poles used currently. One example is a composite pole formed from a single composite wall. In light of the structural design of the pole, the only way to increase the strength of the pole is to add more layers, more weight and consequently, more cost. In addition, poles with a single skin design are susceptible to lateral deflection. Lateral deflection occurs when a pole installed into the ground moves horizontally at its top while the bottom of the pole remains set. Such horizontal movement causes the pole to bend. Again, the only way to compensate for lateral deflection in a single walled pole is to add more layers of composite material thereby adding weight and expense. [19] Lateral deflection was addressed in another pole design disclosed in US Patent 6,286,281. The pole disclosed comprises a plurality of composite panels cut with a taper to form a final pole configuration comprising a taper from bottom to top. To compensate for lateral deflection, a double walled design is disclosed. The two walls are separated by some distance and the cavity formed between the two walls may be filled with foam material. The patent discloses various ways to reinforce the panels to prevent thin wall buckling. For example, the introduction of ribs extending from the inner surface of the panel. Although the design may provide some resistance to lateral deflection, the design does not prevent ovalization at the base of the pole which could lead to collapse of the pole structure in the event of a side impact or other laterally applied external forces. Alternatively, the patent discloses use of V-shaped secondary panels. Such V-shaped panels may only be employed on the flat sides of the pole structure and although the panels may provide some resistance to lateral deflection, the design does not prevent ovalization. In another alternative, the patent discloses using a corrugated secondary panel, wherein the corrugations create a plurality of longi¬ tudinally extending chambers that may be filled with foam. Again, the corrugated design may protect from lateral deflections, however, the design does not have the properties to prevent ovalization of the pole structure. Moreover, use of foam core adds weight and expense to the pole. In addition, due to the foam core, the panels require extra milling to form complete poles thereby adding to the cost of the poles. [20] Accordingly, it is desirable to provide a pole design that provides for increased rigidity, while decreasing deflection with less material and providing the properties to prevent ovalization of the pole. In various embodiments disclosed herein, due to the design of the panels, the walls may be sufficiently thin while at the same time, the panels provide improved resistance to buckling and increased strength properties. Con¬ sequently, production costs and the need for additional guy wires to prevent deflection are also minimized. [21] To minimize weight, provide increased strength, and compensate for lateral deflection, an embodiment of a pole 100 comprising a double walled structure reinforced with a middle corrugated composite is provided herein and shown in FIG. 1. Generally, a pole according to this invention has a predetermined height and outside diameter. Height is determined by the intended application of the pole 100. For example, a common height for the pole 100 may be 45 feet because this height is standard for utility poles in the electrical industry. The diameter of the pole 100 is determined by the die used in a pultrusion process for making the poles 100. To lower production costs, one die may be used for several classes of utility poles. Thus, the pole 100 diameter may not change regardless of the load requirements of the final pole 100. [22] Turning to FIG. 1, a cross sectional view of one embodiment of a pole 100 is il¬ lustrated. The pole may comprise one or more panels 102. Each panel comprises a fibrous material embedded in a resin, discussed further below. The pole 100 comprises a laminate structure, wherein each panel further comprises an outer skin 104 that forms an outer periphery of the panel, an inner skin 106 that forms an inner periphery of the panel and a middle corrugated composite 108 that couples the outer skin 104 to the inner skin 106. As used herein, the term coupling means physically connecting the outer skin 104 to the inner skin 106. [23] In this embodiment, the middle corrugated composite 108 functions to separate the inner skin 106 from the outer skin 104 at a preconfϊgured distance, and further functions to reinforce the panel walls by providing cross brace support sections 110 that span between the inner skin 106 and the outer skin 104. With the two skins 104 and 106 separated, the composite pole 100 has increased rigidity compared to single skin designs and resists lateral deflection better than single skin designs. In addition, the separated skins 104 and 106 provide increased compressive strength that allows the pole 100 to carry heavier weights. [24] According to various embodiments, the skins 104 and 106 may be in parallel orientation with each other, or may comprise orientations other than parallel according to the desired characteristics or desired shape of the pole. In the embodiment shown in FIG. 1, the skins 104 and 106 are oriented parallel to each other. In one embodiment, the inner skin 106 forms a hollow chamber 112 within the pole 100 along the length of the pole 100. [25] The skins 104, 106 and the corrugated middle composite 108 comprise composite materials. In one embodiment, the skins 104, 106 and the corrugated middle composite 108 are formed from a fibrous material and resin composite. The fibrous material may be any suitable fiber material that may give the pole 100 the desired strength, rigidity, weight, or other required characteristics. Fiber types that may be used for the skin materials may comprise for example, fiberglass, carbon, aramid, Kevlar, or natural fibers. Resins comprise for example, any thermoplastic or thermosetting resin including polyester, phenolic resins, or other similar resins. [26] Fibrous materials and the layers of fibrous materials used for the skins 104, 106 and the corrugated middle composite 108 may have several different fiber configurations comprising for example, fabrics, unidirectional rovings, multidirectional rovings, mats or weaves. The skins 104, 106 and the corrugated middle composite 108 may be formed from one layer or a laminate comprised of a plurality of layers of fibrous material. In various embodiments, each layer of fibrous material may have a different configuration. For example, one skin may be formed from three layers of fibrous material. In this embodiment, the first layer may be a plurality of unidirectional rovings oriented in the 0° direction. A second layer may be a woven fabric, and the third layer may be another plurality of unidirectional rovings. In addition, in various embodiments, each layer of the skins 104, 106 and the corrugated middle composite 108 may be formed from a different or same type of fiber. For example, the first layer may be fiberglass, the second layer may be Kevlar, and the third layer may be aramid. The configuration of the skins 104, 106 and the corrugated middle composite 108 is immaterial to the invention. However, it will be recognized by one skilled in the art that increased strength, increased rigidity, and other improved characteristics may be achieved in the skins 104, 106 and the corrugated middle composite 108 by ma¬ nipulating the number of layers, the fibrous materials, or the fiber configurations. [27] In various embodiments, the corrugated middle composite 108 may comprise numerous variations in the fiber configuration as well as variations in the fibrous materials. For example, a fabric or woven material may be used in at least one layer of the corrugated middle composite 108. This unitary piece of fabric material or woven material would ensure a consistent and uninterrupted strength member between the two skins 104, 106 spanning the entire width or circumference of the pole 100 or width of the panel. [28] Although FIG. 1 illustrates a circular pole 100 configuration, various alternate em¬ bodiments are contemplated. For example, in various embodiments, the pole 100 may assume any polygonal or curvilinear cross section. According to the invention, achieving different pole shapes requires the use of differently shaped die and mandrels for the pultrusion process. In alternate embodiments, the outer 104 and inner skins 106 do not have to comprise substantially similar configurations to each other. Throughout the remainder of the specification, the pole 100 will be described as having a circular cross section. However, as just explained, the invention is not limited to that embodiment. [29] Referring again to FIG. 1, the corrugated middle composite 108 comprises cross brace supports 110 that span between the outer skin 104 and the inner skin 106 that are continuous with outer portions 114 that contact and adhere to the outer skin 104 and inner portions 116 that contact and adhere to the inner skin 106. [30] A plurality of middle composite cross brace supports 110 are positioned between the outer skin 104 and the inner skin 106. The characteristics of the pole are affected by the areas of contact 122 and 124 with the skins 104 and 106, respectively, and by the position of the middle composite cross brace support sections 110. For example, the cross braces 110, provide the separation between skins 104 and 106. Each cross brace 110 may migrate between the skins 104 and 106 at an angle # 118 between a skin 104 or 106 and the cross brace 110. This angle # 118 may be any angle between +180° to nearly -180°. Alternatively, the length of the cross brace 110 may be changed to alter the characteristics of the final pole 100. The length and angle # 118 of the cross braces effect the separation between the two skins 104 and 106. As one skilled in the art will understand, the separation of the skins 104 and 106 effects the rigidity and compressive strength of the pole 100. With the corrugated middle composite 108 set between the skins, a plurality of voids 120 are created between the corrugated middle composite 108 and the inner skin 106 and the outer skin 104. These voids 120 are hollow chambers that extend the entire length of the pole 100. [31] An alternate embodiment of the cross section of a pole 500 is illustrated in FIG. 5 A. As discussed above, in various embodiments the pole 500 may be constructed from an outer skin 506, an inner skin 502 and middle composite 508. Similar to the embodiment described in FIG. 1, the skins 506, 502 and middle composite 508 comprise composite materials. In one embodiment, the skins 506 and 502 and the corrugated middle composite 508 are formed from a fibrous material and resin composite. The fibrous material may be any suitable fiber material that may give the pole 500 the desired strength, rigidity, weight, or other required characteristics. In various embodiments, the fiber configurations may comprise for example, fabrics, uni¬ directional rovings, multidirectional rovings, mats or weaves. [32] In this example, the inner skin 502, the outer skin 506 and the middle composite 508 comprise unidirectional fiber rovings embedded in a resin matrix. Similar to FIG. 1, the middle composite 508 comprises a plurality of cross braces coincident with the inner surface 510 of the outer skin 506 and the inner surface 512 of the inner skin 502. In this embodiment, the plurality of middle composite cross braces 508 are oriented substantially perpendicular to the outer skin 506 and inner skin 502. Voids 509 are created between cross braces 508 having a slightly curved substantially rectangular configuration depending on the desired shape of the pole. In this example, the voids 509 are substantially similar in size and shape to each other. However, one skilled in the art will recognize that in various embodiments the voids 509 may comprise variable sizes and shapes with respect to each other. The voids 509 are formed during manufacturing by placement of mandrels between the outer skin 506 and the inner skin 502. The resin wetted fibers are then pulled coincident with the outer 506 and inner 502 skins surrounding the mandrels to form cross braces 508. [33] Still further in this example, the circular pole 500 comprises three mated composite panels 514, 515 and 516. Each panel section 514, 515 and 516 are identical to each other and inverted with respect to the panel on either side so as to enable coupling. In this embodiment, referring to FIG. 5B, each panel 514, 515 and 516 comprises a first end 518 further comprising a female type coupling device 519 and a second end 520 comprising a male type coupling device 521. [34] An expanded view of one panel 514, is shown in FIG. 5B. In FIG. 5B5 the female coupling device 519 is formed from two flanges 522 that extend from the first end 518 of the panel 514. The two flanges 522 further comprise inner knobs 523 to facilitate coupling with male device 521 and in particular, grooves 524. The male coupling device 521 is an extension of second end 520. In this embodiment, the extension comprises two grooved sections 524. The coupling device 521 extends from grooved section 524 outwardly and then inwardly to form a head 526 having an arrow-like con¬ figuration. The head portion 526 inserts into female coupling device 519 and knobs 523 fit within the male coupling device 521 groove sections 524. In a further embodiment, an adhesive may be applied to increase the coupling strength between the panels. [35] In yet another embodiment as illustrated in FIG. 6, a composite pole 600 may comprise a single panel 602 or more than one panel (not shown). In this embodiment, the middle corrugated cross braces 508 shown in FIG. 5A may be substituted for a series of solid or hollow longitudinally extending composite tubes 608 arranged in a configuration to maximize and fill the space between the outer 606 and inner 604 skins. According to this embodiment, the tubes comprise a sufficiently small diameter so as to enable the tubes to fill the space between the skins. According to various em¬ bodiments, the space could accommodate one or more layers of tubes according to the desired characteristics of the end pole structure. It will be recognized by one skilled in the art that there are still other obvious variations of the corrugated composite pole and these examples are not meant to be limiting to these specific embodiments. [36] While FIG. 1 shows that the pole 100 may be constructed as a solid, unitary piece, FIG. 2 shows that a pole 200 may be constructed or formed from a plurality of mated composite panels 202 and 204. Similar to FIG. 5A, Panels 202 and 204 are identical but inverted. In this embodiment, each panel 202 and 204 comprises a first side further comprising a female type coupling device 206 and a second side comprising a male type coupling device 208. The female coupling device 206 is formed from two flanges 210 that extend from a first end 212 of the panel 204. The male coupling device 208 is a projection 214 that extends from the second end 216 of the panel 204. The male coupling device 208 is thinner than the rest of the panel 204 so that it may fit into the female coupling device 206. The female 206 and male 208 coupling devices described herein are only an example of a possible embodiment but not intended to limit the invention. [37] As mentioned above, panel 204 and panel 202 as illustrated in FIG. 2, are identical but inverted. To mate the panels 202 and 204 and construct the pole 100, the male coupling devices 208 are inserted and attached to the female coupling devices 206. The flanges 210 of the female coupling device 206 provide an area to adhesively attach or mechanically attach the panels 202 and 204. Adhesively attaching the panels 202 and 204 means to glue or bond the panels together with a bonding agent. To mechanically attach the panels 202 and 204, a physical device, like a bolt or screw, is used to lock the panels together. [38] In various embodiments, a pole 200 may be formed from more than two panels 202 and 204 as illustrated in FIG. 2. Preferably, the panels comprise equivalent sizes, however, the invention contemplates using panels of varying sizes depending on the desired configuration of the pole. [39] FIG. 3 illustrates an alternate embodiment of the panel 300 coupling devices. In this embodiment, the panel 300 comprises an outer flange 302 that extends from the outer portion 304 of the first end 306 of the panel 300. The panel 300 further comprises an inner flange 308 on the second side 310 of the panel 300. A set of opposing grooves 312 and 314 may be provided on the opposite side of the flanges 302 and 308 to accept the opposing flange on another panel. In this embodiment, the panel 300 accepts another panel (not shown) that is an inverted configuration of the panel 300. [40] To mate or join two panels, the outer flange 302 of a first panel is connected to the outer groove 314 of a second panel and the inner flange 308 is connected to the inner groove 312 of a second panel. As discussed previously, the panel joints may be me¬ chanically strengthened or adhesively strengthened. Method of Manufacture [41] The pole 100 may be manufactured using a pultrusion process. While the pole 100 may be formed as a single piece, it is preferred to manufacture panels and construct the poles from the panels. Smaller fabrics and simpler dies may be used with panels. However, one skilled in the art will recognize how to adapt the pultrusion process to construct a pole from a single panel using an inner mandrel to form the inner periphery 112. The description hereinafter will explain the construction of panels to build poles 100. However, the invention is not limited to that embodiment. [42] In the manufacturing process, fibrous materials are provided for the skins 104, 106 and the corrugated middle composite 108. In this embodiment, the outer skin 104 comprises a first fibrous material, the inner skin 106 comprises a second fibrous material and the corrugated middle composite 108 comprises a third fibrous material. As discussed earlier, in various embodiments, the first, second and third fibrous materials may be different or the same and may further comprise variations within each skin 104, 106 or within the corrugated middle composite 108. [43] The fibrous material may be provided by unwinding or unrolling either fibers or fabrics from a rack or creel. The fibrous materials are wetted out in a resin. Wetting out may be done in a tank, with pre-impregnated tows, or by other processes. The wetted out fibrous materials are then positioned to enter a die. [44] FIG. 4 illustrates positioning of the third materials. To position the third fibrous materials, the materials are interwoven amongst a plurality of corrugation mandrels 402, 404 and 406. These corrugation mandrels 402, 404 and 406 are set between the third fibrous materials creating a pattern of cross braces 410, inner skin connections 412 and outer skin connections 414. The first fibrous materials are placed on the first side 416 of the interwoven third fibrous materials. The second fibrous materials are placed on the second side 418 of the interwoven third fibrous materials. The corrugation mandrels 402, 404, and 406 form the corrugated middle composite 108, compress the skins 104 and 106, and ensure the corrugated middle composite 108 is fused or adhered to the skins 104 and 106 at the inner and outer attachments 114 and 116 as shown in FIG. 1. The mandrels 402 may comprise similar sizes and con¬ figurations but different orientations, for example, are rotated 180° with respect to the mandrel on each opposing side. To form composites with different corrugated middle composite 108 configurations, different shaped and positioned mandrels 402, 404 and 406 may be used. Two end mandrels 404 and 406 help form the ends of the panel. To form a unitary pole, the second fibrous materials are placed around an inner mandrel. The third fibrous materials are interwoven around the corrugation mandrels and are placed around the second fibrous materials. Finally, the first fibrous materials are placed around the interwoven third fibrous materials. [45] After positioning, the fibrous materials are pulled through a die and over the mandrels. The die is configured to the shape of the desired pole or panel. In addition, the length of the mandrels 402, 404 and 406 and dies may be determined by the type of materials used and the amount of heat or curing needed by the panel or pole 100. Heat is applied to the die to cure the resin. After a period of travel through the die, the cured composite panel is pulled from the die. The cured panel may be cooled for a period of time. To create poles 100 of a certain height, the panels may be milled to a pre¬ determined height. Once milled, the panels may be mated to form the completed pole. [46] Once formed, the composite pole 100 may be installed in the field. First, the pole 100 is presented for installation. To present the pole 100, the pole 100 is transported to or is made at the location where it will be installed. A structure to receive the pole 100 at the installation site is created. In one embodiment, a hole is provided in the ground to install the pole 100. This hole may be dug directly into the earth or may be lined with a material, such as concrete. The pole 100 is turned on its end so that the pole 100 stands vertically or nearly vertically. One end of the pole 100 is placed into the structure to receive the pole 100, such as dropping the pole 100 into the ground. The pole 100 may then be stabilized by surrounding the outer periphery with concrete or tamping the ground around the pole 100. In one embodiment, the pole 100 may be stabilized by filling the voids 214 in the pole 100 with a material. In another embodiment, the hollow chamber 108 may be filled with a material. The material may be any substance that can be placed into the voids 214 or hollow chamber 108. These substances may be solids or liquids. For instance, a recycled material may be disposed of inside the voids 214 or hollow chamber. A recycled material may include, but is not limited to, organic waste product from farming operations, ground tires, or con¬ struction waste. [47] Throughout the preceding description, specific embodiments were described and presented in the accompanying drawings. However, it should be understood that the inventions are not limited to those specific embodiments presented. Rather, one skilled in the art will recognize other embodiments or modifications within the scope and intent of the inventions. The inventions are to be construed according to the attached claims.
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