Safety support for use adjacent a vehicular trafficway

[57] ABSTRACT

A tubular support for use in conjunction with a trafficway is provided which has the ability to readily undergo catastrophic rupture when laterally struck by a moving vehicle. The tubular support has a thin wall thickness comprising about 35 to 70 per cent by volume of a resinous matrix, and about 30 to 65 per cent by volume of pyrolyzed carbonaceous fibers containing at least about 90 per cent carbon by weight incorporated with the resinous matrix. The tubular support particularly is suited for the bearing of lighting fixtures, traffic control indicia, utility lines, and the like. When a vehicle which inadvertently has left the trafficway strikes the tubular support, the possibility of bodily injury and vehicular property damage is minimized.

Claims, 3 Drawing Figures

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PATENTED DEC 101974 3,853,418

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3,853,418

SAFETY SUPPORT FOR USE ADJACENT A VEHICULAR TRAFFICWAY

BACKGROUND OF THE INVENTION

In recent years increasing emphasis is being placed upon maximizing the safety of persons engaged in travel, e.g., those moving in vehicular travel along a roadway or other trafficway. In addition to providing the vehicle with safety equipment designed to enhance passenger survival in the event of an emergency, it also has been recognized that hazards posed by fixed objects adjacent the trafficway should be minimized in the event a moving vehicle inadvertently departs from the intended traffic pattern. Those responsible for the design of traffic systems have been faced with a dilemma to some degree since safety devices such as lighting fixtures and traffic indicia, and the like, must by necessity be positioned in relatively close proximity to the trafficway if they are to serve their intended function. However, in the event a vehicle leaves the trafficway either through driver error or mechanical failure, collision with a support for such a safety device commonly results in bodily injury and extensive property damage. Heretofore, it has been difficult to achieve in a support the ability concomitantly (1) to bear on a reliable basis the desired article and (2) to pose no substantial threat to man or property upon impact.

It is an object of the present invention to provide an improved article bearing means for use adjacent a vehicular trafficway for the support of lighting fixtures, traffic control indicia, utility lines, and the like.

It is an object of the present invention to provide an improved high strength article bearing support for use adjacent a vehicular trafficway which readily undergoes catastrophic rupture when struck laterally by a moving vehicle thereby only moderately altering the rate of movement of a vehicle upon impact while minimizing the likelihood of bodily injury or severe property damage.

It is an object of the present invention to provide an improved article bearing means for use adjacent a vehicular trafficway which is lightweight and capable of undergoing easy replacement.

It is another object of the present invention to provide an improved article bearing support which does not undergo decay upon extended exposure to the elements and which exhibits a long life except when laterally struck by a moving vehicle.

It is further an object of the present invention to provide an improved article bearing support for use adjacent a vehicular trafficway which possesses a uniform configuration and which is aesthetically pleasing to the viewer.

These and other objects, as well as the scope, nature, and utilization of the invention will be apparent from the following description and appended claims.

SUMMARY OF THE INVENTION

It has been found that an improved article bearing means for use adjacent a vehicular trafficway for the support of lighting fixtures, traffic control indicia, utility lines, and the like, comprises a high strength elongated tubular member of thin wall thickness having the ability to readily undergo catastrophic rupture when laterally struck by a moving vehicle, wherein the wall of the tubular member comprises (a) about 35 to 70 per cent by volume of a resinous matrix, and (b) about to 65 percent by volume of pyrolyzed carbonaceous fibers containing at least 90 percent carbon by weight incorporated within the resinous matrix.

DESCRIPTION OF THE DRAWINGS

FIG- 1 is a plan view of a vehicular traffic safety system in accordance with the present invention wherein a high intensity lighting fixture is positioned upon a cylindrical tubular support formed from (1) a resinous matrix and (2) pyrolyzed carbonaceous fibers, with said support having the ability to readily undergo catastrophic rupture if struck laterally by a moving vehicle which departs from the adjacent vehicular trafficway.

FIG. 2 is a perspective view of a portion of the cylindrical tubular support of FIG. 1.

FIG. 3 is a perspective view partially cut away of a portion of the vertical tubular support of FIG. 1 wherein a pair of overlying plies of pyrolyzed carbonaceous fibers in the form of flat multifilament tows are exposed.

DESCRIPTION OF PREFERRED EMBODIMENTS

The high strength elongated tubular member of the article bearing means has a thin wall thickness comprising about 35 to 70 percent by volume (preferably 35 to 45 percent by volume) of a resinous matrix, and about 30 to 65 percent by volume (preferably 55 to 65 percent by volume ) of pyrolyzed carbonaceous fibers containing at least 90 percent carbon by weight incorporated in the resinous matrix. The elongated tubular member has the ability to readily undergo catastrophic rupture when struck laterally by a moving vehicle, thereby minimizing the likelihood of bodily injury or severe property damage to the vehicle.

In all instances, the elongated tubular member has a thin wall thickness, and a hollow interior. The wall thickness of the elongated tubular member is preferably about 0.05 to 0.25 inch, and most preferably about 0.07 to 0.12 inch. The elongated tubular member may be provided in any one of a variety of cross-sectional configurations. For instance, the cross-sectional configuration may be circular, rectangular, polygonal, ovoid, etc. A preferred tubular member has a circular crosssectional configuration which may or may not be larger at its base than at the upper terminus.

The resinous matrix may be selected from among those polymeric materials commonly utilized in the production of carbon fiber reinforced composite articles. The resinous matrix may be a thermoset resinous material or a thermoplastic resinous material. The thermoset resinous materials particularly are preferred for use in the present invention, illustrative examples of suitable thermosetting resins for use in production of the tubular member include epoxy resins, thermosetting polyesters, phenolics, polyimides, polybenzimidazoles, etc. The preferred thermosetting resin is an epoxy resin. Illustrative examples of thermoplastic resinous materials include polyamides, polyoxymethylenes, polyolefins (e.g., polyethylene and polypropylene), thermoplastic polyesters, etc. The preferred thermoplastic resin is a polyamide (e.g., nylon 66 formed by the condensation of hexamethylene diamine with adipic acid) or a polyester (e.g., polyethylene terephthalate formed by the condensation of ethylene glycol and terephthalic acid),

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The epoxy resin utilized as the resinous matrix material may be prepared by the condesation of bisphenol A(4,4' isopropylidene diphenol) and epichlorohydrin. Also, other polyols, such as aliphatic glycols and novolak resins (e.g., phenol-formaldehyde resins), acids, or other active hydrogen containing compounds may be reacted with epichlorohydrin for the production of epoxy resins suitable for use as the resinous matrix material. Epoxy resins are preferably selected which possess or can be modified to possess the requisite flow characteristics prior to curing.

Numerous reactive diluents or modifiers which are capable of increasing the flow properties of uncured epoxy resins are well known and include butyl glycidyl ether, higher molecular weight aliphatic and cycloaliphatic mono-glycidyl ethers, styrene oxide, aliphatic and cycloaliphatic diglycidyl ethers, and mixtures of the above.

In preferred embodiments of the invention, epoxy resins are selected to serve as the resinous matrix material which possess terminal epoxide groups and are the condensation product of bisphenol A and epichlorohydrin of the following formula:

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where n varies between zero and a small number less than about 10. When n is zero, the resin prior to curing is a very fluid light-colored material which is essentially the diglycidyl ether of bisphenol A. As the molecular weight increases so generally does the viscosity of the resins. Accordingly, particularly preferred liquid epoxy resins generally possess an n value averaging less than about 1.0. Illustrative examples of standard trade designations of particularly useful commercially available epoxy resins include: Epi-Rez 508, and Epi-Rez 510 (Celanese Coatings), ERL A 2256 (Union Carbide), ERLA 4617 (Union Carbide), and Epon (Shell) epoxy resins.

Epoxy resins formed by the reacting epichlorohydrin with phenol-formaldehyde resins are also particularly preferred thermosetting resins. An illustrative example of highly useful resin is Epi-Rez 5155 epoxy novolak resin (Celanese Coatings).

A variety of epoxy resin curing agents may be employed in conjunction with the expoxy resin. The curing or hardening of the epoxy resin typically involves further reaction of the epoxy or hydroxyl groups to cause molecular chain growth and cross-linking. The term “curing agent” as used herein is accordingly defined to include the various hardeners of the coreactant type. Illustrative classes of known epoxy curing agents which may be utilized include aliphatic and aromatic amines, polyamides, tertiary amines, amine adducts, acid anhydrides, acids, aldehyde condensation products, and Lewis acid type catalysts, such as boron trifluoride. The preferred epoxy curing agents for use with the epoxy resin are acid anhydrides (e.g., hexahydrophthalic acid and methylbicyclo [2.2.1] heptene2,2-dicarboxylic anhydride isomers marketed under the designation Nadic Methyl Anhydride by the Allied Chemical Company), and aromatic amines (e.g., metaphenylene diamine and dimethylaniline).

The pyrolyzed carbonaceous fibers contain at least 90 per cent carbon by weight, and preferably at least per cent carbon by weight (e.g., at least 99 per cent carbon by weight). In a preferred embodiment of the present invention the pyrolyzed carbonaceous fibers exhibit a predominately graphitic x-ray diffraction pattern. The pyrolyzed carbonaceous fibers commonly have a denier per filament of about 0.5 to 2 and a fiber diameter of about 6 to 12 microns and are relatively stiff. Pyrolyzed carbonaceous fibers of larger denier also may be utilized. The pyrolyzed carbonaceous fibers commonly exhibit a mean single filament Young's modulus of at least thirty million psi, e.g., about thirty million to eighty million psi. The Young’s modulus of the fibers may be determined from the mean of the Young’s moduli exhibited by several fibers, measured, for instance by the procedure of ASTM designation D2101-64T, modified in accordance with the tab mounting technique described in AFML-TR-67-159. Additionally, the pyrolyzed carbonaceous fibers commonly exhibit a mean single filament tensile strength of at least about 150,000 psi, and preferably at least about two hundred fifty thousand psi, e.g., about two hundred fifty thousand to five hundred thousand psi. The tensile strength of the fibers may be determined from the mean tensile strengths exhibited by several fibers, mea-

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sured, for instance, by the procedure of ASTM designation D-2101-64T, modified in accordance with the tab mounting technique described in AFML-TR-67-159.

The pyrolyzed carbonaceous fibers may be formed in accordance with a variety of techniques known in the art. For instance, organic polymeric fibrous materials which are capable of undergoing thermal stabilization initially may be stabilized by treatment in an appropriate atmosphere at a moderate temperature (e.g., 200° to 400°C.), and subsequently heated in an inert atmosphere to a more highly elevated temperature, e.g., 1500° to 2000°C., or more, until a pyrolyzed carbonaceous fibrous material containing at least about 90 per cent carbon by weight is formed. The higher the temperature (e.g., within the range of about 2000° to 3100°C.) the more perfect the graphitic structure produced within the same.

The exact temperature and atmosphere utilized during the initial stabilization of an Organic polymeric fibrous material commonly vary with the composition of the precursor as will be apparent to those skilled in the art. During the subsequent carbonization reaction elements present in the fibrous material other than carbon (e.g., oxygen and hydrogen) are substantially expelled. Suitable organic polymeric fibrous materials from which the fibrous material capable of undergoing carbonization may be derived include an acrylic polymer, a cellulosic polymer, a polyamide, a polybenzimidazole, polyvinyl alcohol, etc. Acrylic polymeric materials particularly are suited for use as precursors in the formation of graphitic carbonaceous fibrous materials. Illustrative examples of suitable cellulosic materials include the natural and regenerated forms of cellulose, e.g., rayon. Illustrative examples of suitable polyamide materials include the aromatic polyamides, such as nylon 6T, which is formed by the condensation of hexamethylenediamine and terephthalic acid. An illustrative example of a suitable polybenzimidazole is poly2,2'-m-phenylene-5,5'-bibenzimidazole.

In a preferred technique for forming the carbonaceous reinforcing fibers utilized in the present inven

3,853,418 tion an acrylic fibrous material is stabilized on a continuous basis in accordance with the teachings of commonly assigned U.S. application Ser. No. 749,957, filed Aug. 5, 1968, of Dagobert E. Stuetz (now abandoned) and subsequently is carbonized and graphitized on a continuous basis in accordance with the teachings of commonly assigned U.S. application Ser. No. 244,990, filed April 17, 1972, of Charles M. Clarke.

The pyrolyzed carbonaceous fibers preferably are provided as continuous lengths which substantially are coextensive with the length of the elongated tubular member. For instance, such fibers preferably are multifilament yarns or multifilament tows and are incorporated within the resinous matrix as a plurality of overlying plies. A plurality, e.g., 6 to 100 or more, of multifilament yarn bundles (e.g., each of 200 to 10,000 filaments) may be placed in a parallel side-by-side relationship to form a flat ribbon which serves as a ply. Alternatively, the ply simply may consist of a flat tow, e.g., a tow comprising 1,000 to 100,000 or more, filaments. The thickness of an individual ply may be varied, and commonly ranges from about 1 to 10 mils. The thin wall of the elongated tubular member commonly will comprise about 2 to 30 overlying plies of the pyrolyzed carbonaceous fibers.

The overlying plies present within the wall of the elongated tubular member preferably are balanced with respect to the axis of the elongated tubular member, i.e., are balanced in the sense that a predetermined number of plies are Oriented at an angle —a to the axis of the tubular member and are assembled in an alternating arrangement with a like number of plies at an angle +a to the axis of the tubular member. Such overlying balanced plies preferably are positioned so that the angle a is within the range 30° to 60° with respect to the axis of the elongated tubular member, and most preferably at 45° with respect to the axis of the elongated tubular member.

The elongated tubular member comprising the resinous matrix and the pyrolyzed carbonaceous fibers may be formed through the utilization of fiber reinforced composite technology known in the art. The composite formation technique will be influenced by the nature of the resinous matrix (e.g., whether thermoplastic or thermosetting), the fibrous configuration in which the pyrolyzed carbonaceous fibers are provided, and the overall length and diameter of the desired tubular member. When the resinous matrix is a thermoplastic resinous material, the tubular member may be formed via pultrusion. When the resinous matrix is a thermosetting resinous material, a continuous length (e.g., a ply) of the pyrolyzed carbonaceous fibers may be impregnated with the substantially uncured thermosetting resin and wound about a mandrel utilizing a composite tape laying machine. Once the desired configuration is achieved, the thermosetting resin may be cured through the application of heat and pressure. A vacuum bag autoclave may be utilized in such a formation technique. Because of the relatively small quantities of matrix and fiber required it is possible that the elongated tubular member be formed at the site where it is needed. For instance, piles may be wrapped at the site upon an elastic bladder covering a porous metallic mandrel and the mandrel pressurized to force the assembly into engagement with an outer cylindrical form having internal heaters capable of bringing about the cure of the resin. Regardless of the formation tech6 nique selected commonly there is substantially no waste of resinous matrix material or pyrolyzed carbonaceous fibers. A milling or other analogous operation often associated with the production of a metallic support may be completely eliminated.

The elongated tubular member of the article bearing means particularly is suited for the support of lighting fixtures, traffic control indicia, utility lines, and the like, adjacent a vehicular trafficway. The tubular member exhibits high strength characteristics under static conditions. If desired, a lightweight cross-member may be secured at the upper terminus of the elongated tubular member to aid in the suspension of the article undergoing support. The article bearing means may be incorporated in a traffic safety system wherein its lower end is secured in a substantially vertical position in a mounting means adjacent a trafficway: The mounting means is structured so that it exhibits no substantial impediment to the movement of a vehicle. For instance, the mounting means may comprise a socket of concrete or other durable material which appreciably does not extend above ground level and which engages the lower end of the tubular member.

When a vehicle which inadvertently has left the trafficway strikes the tubular support, the possibility of bodily injury and vehicular property damage is minimized. The tubular support readily undergoes catastrophic rupture when struck by a moving vehicle because of its low impact strength. Little energy is consumed upon impact and the rate of movement of the vehicle is altered only moderately. If utility lines are suspended from a plurality of such tubular supports, the rupture of a single support may result in a portion of the ruptured support, because of its light weight, being suspended between a pair of adjoining supports by the utility lines.

The article bearing support of the present invention offers significant advantages when compared with the prior art. Unlike wooden or metallic poles, the supports of the present invention readily may be handled and moved without resorting to complex equipment. The combination of properties exhibited by the elongated tubular member enables the support reliably to withstand normal environmental conditions such as wind, precipitation, etc. Upon impact, the tubular member immediately ruptures. Such properties are distinct from those exhibited by glass fiber reinforced supports which tend to be heavier and to resist catastrophic rupture upon impact, i.e., they tend to be tough and to bend thereby posing a more substantial danger to passengers.

FIG. 1 illustrates a vehicular traffic system in accordance with the present invention. The thin-walled vertical tubular member 1 has a circular cross-section and is formed of 60 per cent by volume thermoset epoxy resin and 40 per cent by volume of pyrolyzed carbonaceous fibers containing in excess of 99 per cent carbon by weight. The epoxy resin is a condensation product of bisphenol A and epichlorohydrin and prior to curing consists of 100 parts by weight epoxy resin and 88 parts by weight anhydride curing agent. The pyrolyzed carbonaceous fibers are derived from an acrylonitrile homopolymer fibrous material, exhibit a predominately graphitic x-ray diffraction pattern, exhibit a mean single filament Young’s modulus of about sixty million psi, and exhibit a mean single filament strength of about 300,000 psi. The tubular member 1 has a height of 40

3,853,418 feet, a uniform wall thickness of 0.08 inch, an inner diameter at the upper end 2 of 8 inches, and an inner diameter at the lower end 4 of 12 inches. The thin walls of tubular member 1 are essentially void free. The lower portion 6 of tubular member 1 has a constant diameter extending upwardly for 6 feet from its lower end 4. Tubular member 1 has a weight of about 100 pounds.

The lower end 4 of tubular member 1 is mounted in concrete socket 8 having an internal diameter slightly greater than the outer diameter of lower portion 6. The tubular member 1 is secured in concrete socket 8 by fastener 10.

Lightweight transverse arm 12 is constructed of aluminum and is secured at the upper end 2 of tubular member 1 by fasteners 14. High intensity lighting fixture 16 is secured to transverse arm 12. Power line 18 passes through the hollow interior of transverse arm 12 and tubular member 1 and is connected to a circuit breaker present in housing 20 which communicates with underground power line 22. A concrete roadway 24 is in close proximity to the tubular support 1.

A portion of tubular member 1 is illustrated in FIG. 2 wherein its hollow interior is clearly visible. Tubular member 1 is formed through the utilization of a composite tape winding machine wherein continuous lengths of resin impregnated pyrolyzed carbonaceous fibers are wound about a removable mandrel, and subsequently heat cured. Sixteen balanced plies or windings or pyrolyzed carbonaceous fibers are provided in the wall of tubular member 1. Each ply is formed from a multifilament flat tow having a width of about 0.8 inch, and a thickness of about 5 mils. The two consists of about 40,000 filaments which are substantially coextensive in length with the length of the elongated tubular member.

FIG. 3 illustrates a cut away portion of tubular member 1 wherein two of the overlying plies are visible. Each of the sixteen plies is positioned at 45° with respect to the axis of tubular member 1.

Although the invention has been described with preferred embodiments, it is to be understood that variations and modifications may be resorted to as will be apparent to those skilled in the art. Such variations are to be considered within the purview and scope of the claims appended hereto.