Patent Publication Number: US-6712547-B1

Title: Marker post, mold assembly and molding method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to marker posts, and in particular to a square marker post and a mold assembly and method for rotary molding same. 
     2. Discussion of the Related Art 
     Various utilities are commonly placed underground. Examples include fiber optic cables, electrical power lines, gas lines, water lines, steam pipes, pipelines and other utilities. One reason for installing utility lines below grade relates to security and protection, since they are normally relatively well protected from service interruptions caused by the elements and by damage, both intentional and accidental. Another reason relates to aesthetics. Underground installations can eliminate unsightly utility poles and overhead lines. 
     The specific locations of underground utility lines can sometimes be approximated from records, such as drawings prepared in connection with their original installations. However, utility companies and other organizations that utilize underground utilities often provide surface markers showing their locations. For example, the prior art includes elongated, vertical marker posts, the lower ends of which are embedded in the ground above the utility lines. The above-grade, exposed upper ends of such marker posts can be provided with markings, which can identify the utility lines buried thereunder and communicate appropriate warnings. For example, subsurface electrical power and natural gas lines tend to be hazardous to excavators, with attendant risks of electrical shock and explosion respectively. Accordingly, marker posts are used to provide appropriate warnings, such as “Call Before Digging” advisories with toll-free numbers at which additional, pertinent information can be obtained. 
     Subsurface fiber optic and other telecommunications cables are also susceptible to damage from excavators. Severing telecommunications cables can interrupt service unless transmissions can be rerouted. Depending upon the normal traffic volume in a buried cable, significant revenues can be lost before a splice can be made and service restored. Therefore, telecommunications companies naturally attempt to protect their fiber optic cable networks by marking the locations of same with appropriate warnings and information. 
     Prior art marker posts also include concrete constructions with metal plates mounted adjacent to their upper ends. Warnings and other information can be displayed on the metal plates. Other prior art marker post examples include plastic tubes, which can be provided with transverse lengths of tubing at their lower ends for resisting pullout. Such tubular plastic marker posts can mount upper end caps, which can be printed with warning information and color-coded to designate the type of utility buried thereunder. 
     Heretofore there has not been available a marker post and an apparatus and method for manufacturing same with the advantages and features of the present invention. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In the practice of one aspect of the present invention, a marker post is provided, which comprises a generally tubular body with upper and lower ends, a bore extending between the ends and a sidewall structure enclosing the bore. A top panel is mounted on the body upper end and encloses the bore thereat. A base is mounted on the body lower end and includes a base perimeter positioned generally outwardly from the sidewall. The base includes a bottom panel mounted on the base perimeter and having an generally aligned with the bore. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
     FIG. 1 is an upper perspective view of an embodiment/aspect of the invention. 
     FIG. 2 is a bottom perspective view thereof. 
     FIG. 3 is a vertical, cross-sectional view thereof, shown partially buried over a utility line, with a utility line extension located in the marker post. 
     FIG. 4 is a fragmentary, cross-sectional view of the marker post in a rotary mold assembly. 
     FIG. 5 is a fragmentary, cross-sectional view thereof, showing the mold halves removed. 
     FIG. 6 is an end elevational view thereof, taken generally along line  6 — 6  in FIG.  4 . 
     FIG. 7 is a cross-sectional view thereof, taken generally along line  7 — 7  in FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     I. Introduction 
     As required, detailed embodiments and/or aspects of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments/aspects 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. 
     II. Marker Post  2   
     Referring to the drawings in more detail, the reference numeral  2  generally designates a marker post showing one embodiment of the present invention. Without limitation on the generality of useful applications of the invention in its different embodiments, the marker post embodiment  2  as shown in FIG. 3 is partially embedded in earth  4  over a buried, subsurface utility line  6 . Optionally, a utility line extension  8  comprising a conduit  10  receiving conductors  12  mounting wire nuts  14  at their ends can be received within the marker post  2 . In such an application the marker post  2  protects the utility line extension  8  and marks its location for possible future access and connection. For example, an area under development might include a number of utility line extensions  8  received in respective marker posts  2  whereat utility connections can be made in the future as the area develops. 
     The marker post  2  generally includes a body  16  and a base  18 . The body  16  has an upper end  20  and a lower end  22 . The body  16  has a generally square tubular configuration with a sidewall structure  24  comprising four sidewalls  26  enclosing a body bore  28 . Although a square tubular body  16  is shown, other aspects of the invention could include rectangular, multi-sided and circular cross-sectional configurations for the body  16 . 
     A top panel  42  is integrally formed with the sidewall structure  24  and encloses the bore  28  at the body upper end  20 . A graphical display  44  is provided on a respective sidewall  26  in proximity to the body upper end  20  in one aspect of the invention. In other aspects of the invention graphical displays can be placed at other locations and on one or more sidewalls  26 . A ground line  46  is located on one or more of the sidewalls  26  and provides a reference elevation for installing the marker post  2  with a lower portion  48  thereof buried up to the ground line  46  and an upper portion  50  thereof extending upwardly above the existing grade level  52 . 
     The base  18  has a generally square configuration with an upper flange  30  projecting outwardly from the body lower end  22 . The upper flange  30  includes a square inner edge  32  integrally connected to the sidewalls  26  at the body lower end  22  and a square outer edge  34 . A base perimeter sidewall structure  36  includes four base sidewalls  37  depending downwardly from the flange outer edge  34  in generally parallel, spaced relation from respective body sidewalls  26 . A base bottom panel  38  is integrally formed with the base sidewall structure  36  and partially encloses the base  18 . The base bottom panel  38  includes a generally circular opening  40  aligned with the bore  28  and having a diameter approximately equal to a cross-dimension of the body bore  28  between respective opposed pairs of sidewalls  26 . 
     The components of the marker post  2 , i.e. the body  16  and the base  18 , can be integrally formed by rotary molding in one aspect of the invention. The material can comprise any suitable plastic or other material, such as linear low density polyethylene (LLDP). Rotary molding can be accomplished with a rotary molder  54 , which mounts a mold assembly  56  on a rotating arm thereof. The mold assembly  56  includes a mold cavity  80  and first and second mold halves  58 ,  60  each forming a respective body cavity  62 ,  63  and a respective base cavity  64 ,  65 , which cavities generally and collectively conform to the configuration of the finished marker post  2  (FIGS.  4  and  5 ). Each mold half  58 ,  60  includes a respective perimeter flange  66 ,  67 . First perimeter flange  66  mounts multiple nuts  68 , which can be welded in place and receive bolts  70  extending through the second perimeter flange  67  whereby the mold halves  58 ,  60 , can be bolted together along their respective flanges  66 ,  67  during the rotary molding process (FIG.  4 ), and separated for extracting the marker post  2  upon completion of the molding process (FIG.  5 ). The mold halves  58 ,  60 , also include first and second mold bottom halves  75 ,  76 , which collectively form a mold bottom panel  77  with the mold halves  75 ,  76  bolted together. 
     With the mold halves  58 ,  60  secured together (FIG.  4 ), a vent tube  72  is placed in a vent tube receiver  74  formed in the mold bottom panel  76  of the second mold half  60 . The vent tube  72  forms a passage  78  from a mold cavity  80  to atmosphere for relieving pressure in the mold assembly  56  during rotary molding. The mold halves  58 ,  60  include respective U-shaped mold spiders or cradles  82 ,  84  respectively which mount respective lifting lugs  86 ,  88  for suspending the mold assembly  56  on the rotary molder. The mold spiders or cradles  82 ,  84  are welded at their respective ends to the respective mold half flanges  66 ,  67 . 
     The graphical display  44  and the ground line  46  are formed by placing transfer decals  90 ,  92  respectively in the appropriate moid half  58  and/or  60  whereby pigment transfers into the molten LLDP during the molding process. The body  16 , thus infused with the pigment, tends to retain the graphics  44 ,  46  relatively permanently. In one aspect of the invention, the transfer decals  90 ,  92  comprise a hindered amine light stabilizer, although other graphical materials can also be utilized. 
     Upon completion of the molding process and extraction of the molded marker post  2 , the bottom opening  40  can be formed by routing a circle  94  out of the bottom panel  38  (FIG.  5 ). A part line  96  is formed along the body  16  and the base  18  where the mold half perimeter flanges  66 ,  67  meet and can be ground or sanded smooth to remove mold flashing located thereat. In one aspect of the invention, the mold halves  58 ,  60  can comprise sheet metal, such as  12  gauge stainless steel. Alternatively, the mold halves can be cast from aluminum or other suitable material. 
     Is to be understood that while certain embodiments and/or aspects of the invention have been shown and described, the invention is not limited thereto and encompasses various other embodiments/aspects.