Abstract:
A method of manufacturing a marker post includes the steps of preheating a tubular barrel adjacent to a lower end thereof to soften same and deforming the tubular barrel lower end to form a flange assembly. The pre-softened tubular barrel is received in a barrel holder. A mandrel assembly is reciprocated into and out of engagement with the barrel lower end. The mandrel assembly reshapes the barrel lower end to form the flange assembly.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to markers, and in particular to a terrestrial marker post adapted for locating buried utility lines and the like, and a method and apparatus for manufacturing same. 
     2. Description of the Prior Art 
     Marker posts are commonly used for marking the locations of various underground objects. For example, utility lines are often buried. In many locations utility lines are required to be placed underground for aesthetic reasons. 
     In recent years fiber-optic cable networks have been installed in many parts of the country. A common installation procedure involves trenching or boring underground and placing the fiber-optic cables within protective plastic conduit. The fiber-optic cables have many advantages for telecommunications, including the ability to efficiently transmit large amounts of data. However, the potential earnings losses associated with an inoperative fiber-optic cable can be very large, because relatively high revenues are commonly generated from their transfer of correspondingly large amounts of data for telecommunications customers. 
     Excavating equipment and operations pose significant threats to buried utility lines, including fiber-optic cables. Natural gas pipelines, for example, pose an explosion risk. Electrical power lines have attendant risks of damage and injuries related to electrical power. Accidentally severing a buried fiber-optic cable can subject an excavation contractor to significant liability for interrupted service. 
     In order to control such risks, utility companies and service providers have marked the locations of their underground lines and provided information regarding same, such as toll-free numbers, which excavators are encouraged to “call before digging”. A common pre-existing type of marker includes a length of plastic pipe with one end embedded in the ground and the other end mounting a cap. The cap can have printed thereon warning information, and can be color-coded for the type of buried utility, e.g.: blue—water; yellow—natural gas; red—electric; orange (white)—fiber-optic, etc. Such utility markers tend to be relatively effective and are widely recognized. Another advantage is that they are relatively easy to install, but unfortunately many of the prior art designs were easily removed. For example, the surrounding soil can often be loosened by manipulating the above-ground portion of a marker post. The prior art marker posts were thus susceptible to vandalism, theft, etc. A previous solution to this problem involved extending a peg through the embedded portion of the marker post and into the surrounding soil for pullout resistance. However, the pegs and their receivers represented additional components and installation steps, thus adding to the installed costs of the marker posts. Moreover, installing the pegs was sometimes overlooked whereby the marker posts were unprotected. 
     Heretofore there has not been available a marker post and manufacturing method with the advantages and features of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical, cross-sectional view of a marker post embodying the present invention. 
     FIG. 2 is an enlarged, fragmentary, cross-sectional view thereof, taken generally within circle  2  in FIG.  1 . 
     FIG. 3 is a further enlarged, fragmentary, cross-sectional view thereof, taken generally within circle  3  in FIG.  2 . 
     FIG. 4 is a perspective view of a warming tank used in the practice of the method of the present invention. 
     FIG. 5 a  is a top plan view of a barrel holder used in the practice of the method of the present invention. 
     FIG. 5 b  is a fragmentary, top plan view of the barrel holder, particularly showing a mandrel plug thereof advancing into the lower end of the tubular barrel. 
     FIG. 5 c  is a fragmentary, top plan view of the barrel holder, particularly the mandrel plug fully advanced into the barrel lower end. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     I. Introduction and Environment. 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
     Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, “up” and “down” refer to the invention as oriented in FIG.  1 . The words “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the embodiment being described and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof and words of a similar import. 
     Referring to the drawings in more detail, the reference  2  generally designates a marker post embodying the present invention. Without limitation on the generality of useful applications of the invention, the marker post  2  is shown over a buried fiber-optic cable  4 , which is run through buried plastic conduit. The marker post  2 , being hollow, is optionally adapted to receive a length of conduit  6  containing conductors  8 , which can be capped or temporarily terminated (e.g., with wire nuts  10  as shown) for future splicing in connection with a future transformer location or an expansion or extension of utility services. 
     II. Marker Post  2 . 
     The marker post  2  includes a tubular barrel  12  with a bore  14  extending between and open at upper and lower ends  16 ,  18 . The tubular barrel  12  can comprise any suitable thermoplastic material, such as polyethylene, and is formed with a sidewall  20  having interior and exterior surfaces  20   a, b.    
     An annular flange assembly  22  is formed at the tubular barrel lower end  18  and includes an extension portion projecting radially outwardly from the tubular barrel lower end  18 . As shown in FIG. 3, in cross section the extension portion  24  curves through slightly more than 180 degrees, and displays a concave configuration. An annular return portion of the flange assembly  22  extends upwardly and radially inwardly from the extension portion  24 , and terminates at a flange assembly rim  28 . An upwardly-open, annular channel or groove  30  is formed between the tubular barrel outer surface  20   a  and the return portion  26 , and is upwardly-open at an annular channel clearance  32 . The channel  30  is closed at its lower end by the flange assembly extension portion  24 . The configurations of the flange assembly  22  and the channel  30  formed thereby tend to resist pull-out of the implanted marker post  2 . 
     A cap  34  is provided for conveying information, which can be printed thereon and typically comprises a warning such as “WARNING BURIED FIBER OPTIC CABLE IN THIS VICINITY”, together with graphic warnings, contact information such as toll-free numbers, which can be called for additional information, etc. The cap  34  has a closed upper end  36 , which can generally be configured like a hemisphere, and an open lower end  38 . The cap  34  telescopically receives through its open lower end  38  the tubular barrel  12  adjacent to its upper end  16 . The cap  34  can comprise any suitable material, such as a suitable thermoplastic adapted to receive printing thereon by any suitable technique, such as silkscreening. 
     In operation, the marker post is adapted for embedding in soil to a sufficient depth (generally about 1 to 2 feet), as shown in FIG.  1 . Power augers, post hole diggers and other suitable digging tools can be used for digging a hole  40  to receive the marker post  2 . The hole  40  is preferably sized to accommodate the flange assembly  22 , i.e. slightly oversized with respect to the tubular barrel  12 . The concave configuration of the flange assembly  22  facilitates inserting the marker post  2 . Moreover, this concave configuration, with the corresponding curved cross-sectional configuration, provides considerable structural strength for the flange assembly  22 . The marker post  2  is inserted into the hole  40  to refusal, whereat a substantial portion of its length is left aboveground. The surrounding soil  42  is then backfilled around the tubular barrel  12 , and occupies the channel  30  for engagement by the flange assembly  22  whereby the marker post  2  effectively resists pullout. The upwardly-open configuration of the channel  30  tends to resist pullout throughout the embedded length of the tubular barrel  12 . Thus, even lifting the marker post  2  somewhat out of the hole  40  will not cause it to release. Rather, the configuration of the flange is likely to cause the marker post  2  to continue to resist pullout, thus hopefully discouraging its unauthorized removal. 
     III. Manufacturing Method and Apparatus. 
     Without limitation on the generality of useful methods and apparatus for manufacturing the marking post  2 , an exemplary method is described using a manufacturing apparatus  52 , as shown in FIGS. 4,  5   a ,  5   b  and  5   c.    
     FIG. 4 shows a warming tank  54  with an open-top vessel  56  mounting a grid  58 , which provides multiple barrel receivers  58 a adapted for maintaining the tubular barrels  12  in upright positions. Lower portions of the tubular barrels  12  are immersed in heat transfer liquid  60 , which is heated by a thermostat-controlled heater  62  mounted on the vessel  56 . The heat transfer liquid  60  can include glycol or some other suitable component to raise its boiling temperature. The polyethylene tubular barrels  12  soften and become pliable at about 165 degrees Fahrenheit, so the heat transfer liquid  60  temperature can be maintained in the range of approximately 185 degrees to 200 degrees Fahrenheit for effective preheating of the tubular barrels  12  to a softened, pliable temperature. 
     FIGS. 5 a-c  show formation of the flange assembly  22  on a clamping barrel holder  64 , which includes first and second ends  66 ,  68  with respective split sleeves  70  each comprising a fixed or lower half  72  and a movable or upper half  74 . Each upper sleeve half  74  is hingedly mounted on a respective lower sleeve half  72  and is raised and lowered with respect thereto between open and closed positions by a handle  75 . Latching mechanisms  76  are provided for locking the respective sleeves  70  in their closed positions. 
     A mandrel assembly  78  is located at the barrel holder second end  68  and includes a slide subassembly  80  slidably movable between extended and retracted positions (FIGS. 5 a  and  5   c  respectively) by a linear actuator, comprising a piston-and-cylinder unit  81 . Without limitation on the generality of useful linear actuators, a double-acting pneumatic piston-and-cylinder unit is shown and is adapted for connection to a compressed air source  77  through a three-way valve  79 . The valve  79  can including a lever for manual operation, a foot pedal for foot operation, a solenoid for electrical operation, etc. The linear actuator  82  is shown in its retracted position in FIG. 5 a , with a mandrel plug  82  thereof generally aligned with the barrel bore  14  and positioned in close proximity to the barrel lower end  18 . 
     The mandrel plug  82  is generally cylindrical with a distal end  83  chamfered at  83   a  to facilitate insertion into the barrel bore  14  and a proximate end  84  mounted on a mandrel base  85 . The mandrel plug  82  has an annular, convex forming rim  86  (FIGS. 5 b ,  5   c ) located at the junction between its proximate end  84  and the base  85 . The mandrel plug forming rim  86  is adapted for engaging the softened barrel lower end  18  and curving same through an angle of slightly more than 180 degrees, e.g., in the range of about 190 degrees to 220 degrees. As shown in FIG. 5 c , the barrel lower end  18  generally doubles back on itself into engagement with the split sleeve  70 , thus forming the flange assembly  22 . In this position the slide subassembly  80  and the piston-and-cylinder unit  81  driving same are in their fully-extended positions. Retracting the piston-and-cylinder unit  82  retracts the slide subassembly  80  and withdraws the mandrel plug  82  whereby the formed barrel  12  can be removed. 
     It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangement of parts described and shown.