Abstract:
A support structure for use primarily as a lightweight, portable, strong, and fracture resistant tent support and the like, and method for making thereof. The support structure includes a fiberglass core and a resilient outer layer of material that is at least 0.2 millimeters thick. Preferably, the outer layer is made of polyethylene that is between 0.5 to 0.6 millimeters thick, inclusive. In a preferred embodiment, the support structure is curved to conform with the shape of the tent it supports, thereby preventing the support structure from springing back when inadvertently released from the tent. More preferably, the support member includes a plurality of elongate curved sections that are detachably secured together to form the support member.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/120,716 filed on Feb. 16, 1999, and Australian Provisional Application No. PQ2112 filed on Aug. 9, 1999. 
    
    
     TECHNICAL FIELD 
     The invention is an improved support member for use primarily as a lightweight, portable, strong, and fracture resistant tent support and the like, and method for making thereof. 
     BACKGROUND OF THE INVENTION 
     There is a need for lightweight, portable, strong, and fracture resistant support structures. For example, it is desirable for tents to be as lightweight, easy to assemble and disassemble, and compact as possible when collapsed. Accordingly, the support structure must be equally portable, and lightweight, but sufficiently strong to support the tent when assembled. 
     Moreover, tents are now used for a wide variety of functions. For example, in addition to the typical hiking and camping functions, tents, which may be readily shaped and decorated to resemble playhouses, sports accessories, or vehicles, are now commonly used as children&#39;s toys. Accordingly, their support structures must be particularly safe to assemble, disassemble, and use. 
     As shown in FIG. 1, the typical tent support structure  10  includes a plurality of hollow elongate straight sections  12 , constructed typically of elongate strands of fiberglass secured and hardened together with an appropriate resin. The sections  12  each include mating end portions  14  that interconnect with each other to allow the sections  12  to be detachable secured together to form the elongate straight support structure  10 . An elongate elastic element  15  may extend through the hollow core securing the sections  12  together. Known tent support structures are secured within pockets or loops  18  attached to the tent  16 . The structures are then bent and held in place such that they are placed in tension, thereby supporting the tent  16 . 
     Another form of portable tent support includes interfitting sections of metal tubular poles, such as aluminum, end-to-end. Each such section includes a mating end portion for detachably securing it with an adjacent end of another section, thereby producing the extended pole. 
     While these types of conventional support members are economical to manufacture, lightweight, and easy to assemble and disassemble, they have several limitations that affect their desirability, particularly when used in tents for children&#39;s use. For example, when excessive bending force is applied to these known fiberglass supports, such as by a child falling on or throwing a heavy object onto the tent, as best shown in FIG. 2 the strands of fiberglass tend to splinter exposing shrouds  19  of fiberglass and causing an extreme safety hazard. On the other hand, known metal supports tend to bend permanently when excessive force is applied, rendering them useless. 
     Moreover, because the typical fiberglass support is under tension during use, known fiberglass supports have a tendency to spring back into their straight positions when the tent fails or the support is moved out of its secured position within the tent, such as when a child inadvertently plays with the support structure. The spring back motion poses a safety risk to the user, particularly to small children playing within a toy tent. 
     Inventors have attempted to overcome these problems by attempting to make fiberglass support structures stronger. For example, U.S. Pat. No. 4,172,175 to Pearson et al. (“Pearson”) discloses a fiberglass pole construction method that includes placing layers of elongate fiberglass strands in alternating directions to produce a strong hollow pole. The strands of fiberglass are held in place during manufacturing by “thin lateral bands 56” (See, FIG. 5 of Pearson). The bands are constructed with “a fused polymeric material such as polyethylene which has a lower melting point than the glass fibers.” (Pearson, col. 3, lines 48-50). The bands serve to hold the fiberglass strands aligned during the manufacturing process. The fiberglass resin is then heated during the curing process, and the bands melt away while the resin hardens. 
     The resulting alternating layers of orthogonally aligned fiberglass fibers in Pearson provide an essentially rigid and strong pole. However, it is not well suited for use as a tent support for at least the following reasons: First, the pole is not particularly flexible along its longitudinal length making it difficult at best to place the pole in tension to support the tent. Second, when an inadvertent breaking force is applied to the pole, shrouds of fiberglass are still exposed, causing a significant safety risk, particularly to young children. And third, it is expensive to build. 
     Accordingly, despite these types of improvements, there remains a need for a support structure that is strong, portable, and economical to manufacture, but also is fracture resistant and safe to assemble and use. In addition to other benefits that will become apparent in the following disclosure, the present invention fulfills these needs. 
     SUMMARY OF THE INVENTION 
     The present invention is a support structure that includes a fiberglass reinforced core portion and an elastic outer layer, which is preferably polyethylene, and a method for making there same. More preferably, the support structure may include a plurality of elongate curved sections having a hollow core, and the sections may be detachably secured together to define an assembled position and form the support member having the shape of the structure or tent they are meant to support. An elongate resilient element may extend through the hollow core securing the sections together and urging them to retain their assembled position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 (Prior Art) is a top plan view of a conventional fiberglass support structure in its disassembled configuration. 
     FIG. 2 (Prior Art) is a fragmentary exploded plan view of a conventional fiberglass support showing a possible fracture. 
     FIG. 3 is an isometric view of a tent having support members in accordance with a preferred embodiment of-the invention. 
     FIG. 4 is a top plan view of a support member in accordance with a preferred embodiment of the present invention showing a possible disassembled configuration. 
     FIG. 5 is a side plan view of the support member of FIG. 4 showing a possible assembled position. 
     FIG. 6 is a fragmentary exploded plan view of a support member in accordance with a preferred embodiment of the present invention showing the initial stages of a possible fracture. 
     FIG. 7 is the support member of FIG. 3 showing the completed fracture. 
     FIG. 8 is a cross sectional view of the support member of FIG. 7 taken along line  8 — 8  of FIG.  7 . 
     FIG. 9 is a cross sectional view of an alternative preferred support member in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An elongate improved support member  20  having a fiberglass core  22  with an outer surface ( 23 , FIG. 8) and a durable outer layer  24  of elastic material, preferably constructed of polyethylene and having a smooth exterior surface  26  is disclosed in FIGS. 3-8. 
     General Assembly 
     As best shown in FIGS. 4,  5  &amp;  8 , the support member  20  preferably includes a plurality of discrete sections  28 . Each section  28  includes a hollow center  30 , the fiberglass core  22  and the outer layer  24  of elastic material, which is preferably polyethylene at least 0.02 millimeters thick. 
     Preferably, each section  28  includes mating end portions  32  for detachably securing the discrete sections  28  together. In particular, the end portions  32  are rigidly secured to one end  34  of each discrete section  28  and have a section retention portion  36  for detachably receiving the free end  38  of another discrete section  28 . Accordingly, as best shown in FIG. 5, the discrete sections  28  may be detachable secured together end-to-end to form the elongate support member  20  defining an assembled position  40 . End caps  42  are secured within the open ends of the support member  20 . 
     More preferably, the discrete sections  28  are curved, and an elongate resilient element  44  extends through the hollow center  30  of each discrete section  28  securing the discrete sections  28  together and urging them to retain the support in its assembled position  40 . 
     Preferred Construction Method 
     The elongate fiberglass core  22  of the discrete sections  28  is preferably constructed with traditional methods such as by extruding a continuous length of fiberglass tubing and cutting the discrete sections  28  to length. The fiberglass core  22  preferably includes elongate strands of fiberglass secured within an appropriate resin. In situations where it is desirable for the discrete sections  28  to be curved, the extruding process must be modified to produce curved fiberglass core. 
     The outer layer  24  of resilient material is then installed on the fiberglass core. Preferably, the polymer outer layer  24  is a cylindrical section of polyethylene tubing having an inside diameter sized to just receive the fiberglass core  22  and a length slightly longer than the fiberglass core to ensure coverage of the fiberglass member. 
     In order to obtain meaningful strength and fracture improvements while retaining the elasticity of the support member in accordance with the objects of the present invention, the polyethylene outer layer  24  should be at least 0.2 millimeters thick. More preferably, the polyethylene outer layer  24  is between 0.2 to 1.0 millimeters thick, inclusive. Optimal performance is achieved when the polyethylene outer layer  24  is between 0.5 millimeters to 0.6 millimeters thick. 
     Preferably, the polyethylene is high density polyethylene, but desirable results can also be achieved with low density polyethylene. Similarly, materials having similar strength, elasticity, and formability characteristics to polyethylene, such as polyvinyl chloride (“PVC”), vinyl, polypropylene, polyurethane, rubber and latex can be used in place of polyethylene to produce the desirable results. However, polyethylene is the preferred material because of its low cost and ease of manufacturing, and it results in a support structure having optimal strength and elasticity characteristics. 
     After the fiberglass core  22  is placed within the polyethylene tubing, the assembly is passed through an appropriate heating device (not shown) to cause the polyethylene tubing to shrink into a tight fit over the fiberglass core  22  and to bond the polyethylene tubing onto the fiberglass core  22 . To obtain maximum structural enhancement, the polyethylene should form a continuous layer around the fiberglass core. This could include complete inner and outer encapsulation of the fiberglass core  22  by the polyethylene. 
     The temperature to which the polyethylene tubing is heated is selected to cause the polyethylene to be heat welded to the fiberglass core  22 , but below the temperature at which the polyethylene or the fiberglass deteriorates. The heating process also caused those portions of the polyethylene tubing overlapping the ends of the fiberglass core to shrink over the ends of the fiberglass core and heat welded thereto. 
     After the polyethylene outer layer  24  is bonded to the fiberglass core  22 , the mating end portions  32  are secured to each discrete section  28  with conventional methods. Then, the elongate resilient element  44  is extended through the hollow center  30  of each discrete section  28  and secured in place, such as by inserting stop members (not shown) at each end of the support member  20 . Finally, the end caps  42  are secured on the opposite ends of the support member  20 . 
     Operation of the Support Member 
     A user assembles and uses the support member  20  much like a traditional fiberglass support member  10 . From a compact position  46  shown in FIG. 4, the discrete sections  28  are aligned end-to-end and the free end  38  of each discrete section  28  is inserted into the section retention portion  36  of each adjacent discrete section  28 , thereby placing the support member  20  in its assembled position  40  shown in FIG.  5 . The support member  20  is then inserted in the sleeve or loops  18  of a tent (or flexible shell)  16 , thereby supporting the tent  16 . 
     In cases where the discrete sections  28  are straight, the resulting support member  20  operates like a conventional support. It is bent about two points, placing the support member  20  in tension and forming a curve that conforms to the shape of the tent. In such case, should the tent  16  rip or the support member  20  become dislodged, the support member  20  will attempt to spring-back into its straight position like a conventional support. 
     However, in cases where the discrete sections  28  are curved as shown in FIG. 4, they are preferably shaped such that when the support member  20  is in its assembled position  40 , the support member  20  has a neutral shape that conforms with the shape of the tent  16  that it supports. In such case, the support member  20  is not essentially spring-loaded, and the risk of the support member  20  springing back should the tent rip or the support be inadvertently moved out of position is greatly reduced. 
     Testing also reveals that the addition of the polyethylene outer layer  24  to a fiberglass core  22  provides numerous benefits. For example, the polyethylene outer layer  24  has a smooth exterior surface  26  that reduces wear to the tent  16  without significantly increasing the cost of production. Also, testing indicates that the support member  20  retains its elasticity despite the presence of the polyethylene outer layer  24 . 
     In addition, the support member  20  is much stronger than conventional fiberglass supports. In particular, a compression strength test was conducted comparing the strength between a control sample comprising a length of conventional 7 mm diameter fiberglass pole and a 7 mm diameter fiberglass pole having an polyethylene outer layer  24 . The lengths of poles were each tested by extending them horizontally over two supports that were spaced 300 mm apart and securing them in place. A V-shaped block was placed on top of the poles and centered between the supports. An increasing compression force downward was then applied by the block to each pole until it fractured. The amount of force required to fracture each pole was then recorded. The control sample fractured when forces ranging between 26.38 kgf to 29.38 kgf were applied. In contrast, the fiberglass core having the polyethylene outer layer  24  fractured when forces ranging between 34.94 kgf to 36.54 kgf were applied, indicating it is roughly 40% stronger than the control sample. 
     Moreover, as best shown in FIGS. 6 &amp; 7, when the support member  20  does fracture, the polyethylene outer layer  24  covers the resulting shrouds of fiberglass, preventing them from posing a safety hazard, and thereby further reducing the likelihood of injury. 
     In view of the wide variety of embodiments to which the principles of the invention can be applied, it should be apparent that the detailed description of the invention is illustrative only and should not be taken as limiting the scope of the invention. For example, the fiberglass core  22  could be constructed with any known means or methods, including molding, and the like. Moreover, the polyethylene outer layer  24  can be applied with a variety of methods including wrapping a sheet of polyethylene around the fiberglass core  22  and heat welding the overlapping polyethylene sheet to itself and onto the fiberglass core at the same time to form a seamless layer around the fiberglass core. It will also be appreciated that the polyethylene outer layer  24  may also be structurally bonded to the fiberglass core  22  using an adhesive or intermediate layer without departing from the scope of the invention. 
     To obtain the desired results, the elastic material only has to cover the fiberglass core. Accordingly, as shown in FIG. 9, an intermediate layer  50  of suitable material may be sandwiched between the outer surface  52  of the fiberglass core and the polyethylene without departing from the scope of the invention. Similarly, one or more layers of material  54  may be placed over the external surface  26  of polyethylene layer without departing form the scope of the invention. 
     Also, while the outer layer  24  is preferably constructed with polyethylene, other materials having similar physical properties may be substituted such as PVC, vinyl, polypropylene, polyurethane, rubber and latex. 
     Accordingly, the claimed invention includes all such modifications as may come within the scope of the following claims and equivalents thereto.