Patent Publication Number: US-10328614-B2

Title: Method and apparatus for extracting columns from molds

Description:
RELATED APPLICATIONS 
     The present application is a continuation-in-part of U.S. application Ser. No. 14/991,137, filed Jan. 8, 2016, which claims the benefit of U.S. Provisional Application Ser. No. 62/101,693 filed Jan. 9, 2015, the disclosure of each is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to molded columns and, more particularly, to methods and apparatus for manufacturing molded columns. 
     BACKGROUND 
     Columns are widely used in both residential and commercial buildings. Until recently, most columns used in residential construction have been made from wood. Molded columns, however, have some advantages over traditional wood columns and have been gaining in popularity. Some of the advantages of molded columns include lower costs, a wider variety of designs, and improved structural strength. 
     One technique for making molded columns is centrifugal molding. A viscous resin material is poured into an elongated mold having two parts. The mold is spun at high speed to force the molding material against the inner surface of the mold. When the molding material has set, the mold is opened and the column is removed. 
     One drawback to centrifugal molding is that the mold leaves two longitudinally extending seam lines or ridges where the mold separates. The seam lines or ridges must be removed to provide a smooth exterior surface. Typically, the seam line or ridge is removed by manually sanding the column. However, the manual sanding of molded columns is time consuming and labor intensive. The time and labor needed to sand the column translates into higher cost and lower production. 
     BRIEF SUMMARY 
     The present invention relates generally to the manufacture of molded columns by centrifugal or rotational molding processes. The columns are molded in an elongate tubular mold that is closed at one end and open at the opposite end for forming the molded parts. The mold includes a flexible sidewall that is made of a resilient material that can radially expand and return to its original condition. The sidewall of the mold is made of a single piece and does not include a parting line. The inner surface of the mold may comprise a recessed or protruding form to mold a protruding or recessed relief on or in an exterior surface of the molded part. After the column is formed, pressurized gas is introduced to the interior of the mold. The pressurized gas expands the sidewall to separate the sidewall of the mold from an exterior surface of the column. The column can then be pulled axially through the open end of the mold, even when the exterior surface of the column includes protruding or recessed details. 
     Another aspect of the disclosure comprises a gripping tool used to extract the column from the mold. The gripping tool is inserted into the interior of the column through the open end of the mold. The gripping tool is expanded to engage an inner surface of the column. The gripping tool includes an eyelet, hook, or other feature that is engaged by a pulling device to pull the column from the mold. 
     In some embodiments, the gripping tool comprises an expandable plug having a flexible sidewall. Pressurized gas is supplied to an interior of the expandable plug to expand the sidewall of the expandable plug into contact with the inner surface of the column. When the expandable plug is in place, pressurized gas is introduced into the interior of the elongate molded part through the plug to expand the mold before pulling the column through the open end of the mold. 
     In other embodiments, the gripping tool comprises a shaft and two or more wing members pivotally connected to the shaft. The wing members are configured to expand when pivoted away from said shaft and to retract when pivoted toward said shaft. Biasing members may be provided to bias the wing members towards and expanded position. 
     Although this disclosure focuses on the manufacture of molded columns, the techniques herein described are more generally applicable to any elongate molded part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a molding apparatus for molding columns including a mold and mold housing. 
         FIG. 2  is a perspective view of the molding apparatus with the mold inserted into an open mold housing and open end of the mold raised to allow introduction of molding material into the mold. 
         FIG. 3  is a perspective view of the molding apparatus with the mold inserted into the open mold housing. 
         FIG. 4  is a perspective view of the molding apparatus with the mold housing closed. 
         FIG. 5  is a perspective view of an exemplary mold and end cap for sealing the open end of the mold. 
         FIG. 6  illustrates a spinning apparatus for rotating the mold. 
         FIG. 7  is a perspective view of an apparatus for extracting molded columns from molds. 
         FIGS. 8A and 8B  illustrate an expandable plug for pulling a molded column from a mold. 
         FIGS. 9A-9C  are schematic diagrams illustrating the basic process of extracting a molded column from a mold. 
         FIGS. 10A-10G  illustrate a method of using air pressure to extract a molded column from a mold. 
         FIGS. 11A-11C  illustrate an apparatus for releasing a mold from a molded column. 
         FIG. 12  illustrates an expandable gripping device for pulling a molded column from a mold. 
         FIG. 13  illustrates an expandable gripping device for pulling a molded column from a mold. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, a molding apparatus  10  and extraction equipment  100  according to an exemplary embodiment of the disclosure is shown. The molding apparatus  10 , in general, is used to mold a column  5  from a suitable molding material by centrifugal or rotational molding. To briefly summarize, the molding material, such as a polyester resin, is poured into a mold  20 . The molding material is initially in a viscous state, and subsequently hardens to form the molded part. In one embodiment, the molding material comprises a blend of polyester resin and powdered marble containing approximately 25% to 35% polyester resin. The mold  20  is rotated by a spinning machine  30  so that the centrifugal force causes the molding material to flow against the inner surface of the mold  20 . The mold  20  is rotated until the molding material has had sufficient time to set thus forming a column  5 . Extraction equipment  100  is then used to extract the molded column  5  from the mold. 
     As will be described in more detail below, the mold  20  is a single piece mold that is open at one end. The molded column  5  is extracted by pulling the molded column  5  axially through the open end of the mold  20 . Single piece molds have not been used in the past because of the difficulty of extracting the molded part from the mold  20 . If the molded column  5  does not release from the inner surface of the mold  20 , pulling the molded column  5  through the mold  20  may mar the molded column  5  and/or damage the mold  20 . Another problem is that the molded columns  5  may include features, such as rings, astragals or sculptural reliefs that normally prevent the molded column  5  from being extracted in an axial direction. This disclosure describes techniques for axially extracting a molded column  5  or other elongate structure from a mold without marring the surface of the molded part or damaging the mold. The techniques herein described may be used even when the molded part includes rings, sculptural reliefs, or other profiles that would normally prevent axial extraction of the molded part from the mold  20 . 
       FIG. 1  is an exploded perspective view of an exemplary molding apparatus  10  for making columns  5  or other elongate members. The molding apparatus  10  generally comprises a mold  20  for forming the molded part and a spinning machine  30  for rotating the mold  20  while the molded part is being formed. 
       FIG. 5  illustrates an exemplary mold  20 . The mold  20  comprises a flexible sidewall  22 , a closed end  24 , and an open end  26 . The flexible sidewall  22  is made of a resilient material, e.g., silicone rubber, that can radially expand and return to its original condition. The sidewall  22  of the mold  20  is preferably made of a single piece and does not include a parting line. The sidewall  22  includes an inner surface  28  that conforms to the desired shape of the molded column  5 . In this example, the inner surface  28  of the mold  20  generally defines a generally circular cylinder that tapers outwardly from the upper end of the column  5  to the lower end of the column  5 . It will be appreciated, however, that the mold  20  may be designed to produce columns  5  of virtually any geometric shape including square columns  5 , rectangular columns  5 , oval or elliptical columns  5 , or hexagonal columns  5 . The column  5  may include recessed or protruding features such as flutes, rings, sculptural reliefs, or other molded profiles that extend out of or into the exterior surface of the column  5 . Therefore, the inner surface  28  of the sidewall  22  may include a recessed or protruding form to mold a protruding or recessed feature or in an exterior surface of the column  5 . In the exemplary embodiment shown in  FIG. 5 , the inner surface  28  of the mold  20  includes an annular channel  30  having the profile of a desired architectural molding for forming a ring or astragal that encircles or surrounds the exterior surface of the column  5 . 
     The spinning machine  30 , as previously described, rotates the mold  20  while the column  5  or other molded part is being formed. The spinning machine  30  comprises a mold housing  40 , support frame  70 , and drive assembly  90 . The mold  20  inserts into a cavity  50  in the mold housing  40 . The mold housing  40  is rotatably mounted to the support frame  70 . A drive assembly  90  including a drive motor  92  rotates mold housing  40  about a longitudinal axis that coincides with the center line of the mold  20 . The rotation of the mold  20  within the mold housing  40  cause the material in the mold  20  to flow radially outward into contact with the inner surface  28  of the sidewall  28 . The rotation of the mold  20  continues until the molding material sets. 
     The mold housing  40  is illustrated in  FIGS. 1-4 . The mold housing  40  includes a first housing section  42  and second housing section  44  which may be separated. The first and second housing sections  42 ,  44  comprise box-like casings made of wood, metal fiberglass, or other suitable material that are filled with epoxy. Stiffening members  45  are affixed to outer surface of the housing sections  42 ,  44  to impart strength and rigidity to the housing section  42 ,  44 . The first and second housing sections  42 ,  44  include flat mating surfaces  46  and  47  formed by the epoxy filling. The epoxy filling in the first and second housing sections  42 ,  44  define a cavity  50  configured to receive the mold  20 . The cross-section of the cavity  50  when the mold housing  40  is assembled conforms to the exterior cross-section of the mold  20 . The cavity  50  is long enough to receive the mold  20  with a small gap between the open end  26  of the mold  20  and the end of the cavity  50  to receive an end cap  36  ( FIG. 5 ) used to close the open end  26  of the mold  20  during the molding process. 
     In some embodiments, the mating surfaces  46 ,  47  of the first and second housing sections  42 ,  44  may include complimentary locating features  54  for aligning the first and second housing sections  42 ,  44 . The first and second housing sections  42 ,  44  are secured together by latches  58 . The type of latch is not a material aspect of the mold housing  40 . For example, the latches  58  may comprise conventional draw latches including a first latch part including a loop  60  that engages with a second latch part including a hook  62 . 
     The mold housing  40  includes mounting plates  48  attached at each end of the first housing section  42 . A mounting shaft  52  extends from each mounting plate  48  along the longitudinal centering of the mold housing  40  for rotatably mounting the mold housing  40  to a support frame  70 . 
     The support frame  70  includes first and second frame sections  72 ,  74  disposed at opposite ends of the mold housing  40 . The first and second frame sections  72 ,  74  may be interconnected by connecting members  76 . In one exemplary embodiment, the first and second frame sections  72 ,  74  include pillow bearings  78  ( FIG. 6 ) shielded by an enclosure to receive the mounting shafts  52  extending from opposite ends of the mold housing  40 . 
     A drive assembly  90  including a motor  92  is provided for rotating the mold housing  40 . In some embodiments, a direct drive arrangement may be used wherein the motor  92  is directly coupled to one of the mounting shafts  52  and rotates the mold housing  40 . In one embodiment, a gear box  94  and drive pulley arrangement  96  may be interconnected between the drive motor  92  and mounting shaft  52  at one end of the mold housing  40  as shown in  FIG. 6 . The particular arrangement of the drive assembly  90  is not a material aspect of the disclosure. In the embodiment shown in  FIG. 6 , a drive pulley is mounted to the output shaft of gearbox  94  and is connected by a belt to a driven pulley on one of the mounting shafts  52 . 
       FIGS. 2-4  illustrate an exemplary process for making a molded column  5  using the molding apparatus  10 . The mold  20  is inserted into the mold cavity  50  and the open end  26  of the mold  20  is elevated ( FIG. 2 ). A block may be inserted beneath the mold  20  as shown in  FIG. 2  to help hold the open end  26  of the mold  20  in an elevated position. A molding material is poured into the open end  26  of the mold  20 . Once the molding material is poured into the mold  20 , the open end  26  is lowered into the mold cavity  52  of the second housing section  44  and the end cap  36  is inserted between the open end  26  of the mold  20  and the end wall of the cavity  50  to seal the mold  20  ( FIG. 3 ). The second housing section  44  is then lowered onto the first housing section  42  and the latches  58  are engaged to secure the first and second housing sections  42 ,  44  together ( FIG. 4 ). 
     The mold housing  44  and mold  20  are then rotated for a predetermined period of time depending upon the properties of the molding material. In general, the mold housing  40  and mold  20  are rotated for a sufficient amount of time to allow the molding material to set and form the molded column  5 . When the mold  20  is rotated, the material inside the mold  20  flows outward against the inner surface  28  of the mold  20 . Once the molding material has had sufficient time to set, the rotation of the mold  20  is stopped and the mold  20  is removed from the mold housing  40 . The extraction equipment  100  is then used to extract the molded column  5  from the mold  20 . 
       FIG. 7  illustrates the extraction equipment  100  used to extract the molded column  5  from the mold  20 . The extraction equipment  100  generally comprises a work table  102 , a holding fixture  108  disposed on the work table  102 , an expandable plug  120  for insertion into the molded column  5 , an air supply system  150  for supplying air to the interior of the molded column  5 , and a pulling device  160  for pulling the molded column  5  from the mold  20 . 
     The work table  102  comprises an elongated work surface  104  that is supported by a support frame  106 . The holding fixture  108  is disposed at one end of the work surface  104 . The holding fixture  108  comprises end plates  110 , 112  and one or more supports  116 . When the mold  20  is inserted into the holding fixture  108 , the closed end of the mold is placed against the end plate  110  while the open end  26  of the mold  20  is disposed towards end plate  112 . End plate  112  includes an opening  114  that is large enough for the molded column  5  to pass through. The supports  116  include arcuate support surfaces that generally conform to the shape of the mold  20 . When the mold  20  is placed in the holding fixture  108 , the supports  116  support the mold  20  so that the mold  20  is actually aligned with the opening  114  in the end plate  112 . 
     The expandable plug  120 , shown in  FIGS. 8A and 8B , is configured to be inserted through opening  114  in end plate  112  and the open end  26  of the mold  20  into the interior of the molded column  5 . The expandable plug  120  functions as a gripping tool to grip and inner surface of the molded column  5 . The expandable plug  120  includes an outer plate  122 , inner plate  124 , core member  126 , and flexible side wall  128 . The outer plate  122  and inner plate  124  are secured to the core member  126  by screws, bolts or other suitable fasteners. The outer plate  122 , inner plate  124 , and core member  126  may be made of wood or plastic material. The sidewall  128 , which may be made of a natural rubber, synthetic rubber, or other elastic material, surrounds the core member  126 . The core member  126  includes channels  130  that interlock with protrusions  132  at the ends of the sidewall  128  to hold the sidewall  128  in place. A first air passage  134  in the core member  126  communicates with the space between the core member  126  and sidewall  128 . A second air passage  136  extends through the end plate  122 , core member  126  and end plate  124  to communicate with the interior of the molded column  5 . The first and second air passages  134 ,  136  connect to inlet tubes  138 ,  140  with quick connect couplings for coupling the inlet tubes  138 ,  140  to air supply lines  154 ,  156  as hereinafter described. An eyelet  144  is secured to the core member  126 . As will be described in more detail below, the eyelet  144  is used to pull the molded column  5  from the mold  20 . 
     Referring back to  FIG. 7 , the air supply system  150  comprises an air compressor  152  and air supply lines  154 , 156 . The air compressor  152  serves as a source of pressurized gas and may comprise two outlets that provide air at different pressures. Alternatively, the source of pressurized gas may comprise two separate air compressors, each providing air at a different pressure. A first air supply line  154  connects a first outlet of the air compressor  152  to the first inlet tube  138  of the expandable plug  120 . A second air supply line  156  connects a second outlet of the air compressor  152  to the second air tube  140  of the expandable plug  120 . As will be described in more detail below, the air pressure applied via the first air supply line  154  to the interior of the expandable plug  120  should be sufficient to prevent the ejection of the plug  120  when the interior of the column  5  in pressurized and to provide enough gripping force to pull the molded column  5  through the open end  26  of the mold  20 . 
     The pulling device  160 , shown in  FIGS. 9A-9C , comprises a winch  162  and cable  164 . A hook  166  is disposed at the free end of the cable  164 . The hook  166  is configured to engage with the eyelet  144  on the expandable plug  120 . When the winch  162  is actuated, the cable  164  and hook  166  apply an axial force to the expandable plug  120  to pull the molded column  5  out through the open end  26  of the mold. 
       FIGS. 9A-9C  schematically illustrate the process for extracting the molded column  5  from the mold  20 .  FIG. 9A  shows the expandable plug  120  inserted into the molded column  5  through the open end  26  of the mold  20 . Air supply lines  154  and  156  are connected respectively to the first and second air tubes  138 , 140  respectively. The hook  66  of the cable  164  is engaged with the eyelet  144  on the expandable plug  120 . In one embodiment, air pressure in the range of about 10-40 psi is applied via the first air supply line  154  to the interior of the expandable plug  120  causing the sidewall  128  of the expandable plug  120  to expand radially outward and engage the inner surface of the molded column  5 . The engagement of the sidewall  128  of the expandable plug  120  with the inner surface of the molded column  5  also seals one end of the molded column  5 . In one embodiment, air pressure in the range of about 20-80 psi is then applied via the second air supply line  156  to the interior of the molded column  5 . As will be described in more detail below, the air pressure supplied to the interior of the molded column  5  causes the mold  20  to expand and release from the molded column  5  so that the molded column  5  can be pulled through the open end  26  of the mold  20 . In  FIG. 9B , the winch  162  is actuated while air is applied to the interior of the column  5  to pull the molded column  5  through the open end  26  of the mold  20 .  FIG. 9C  shows the column  5  fully extracted from the mold  20 . 
       FIGS. 10A-10G  illustrate in more detail how air pressure supplied to the interior of the molded column  5  facilitates extraction of the molded column  5  from the mold  20 .  FIG. 10A  shows the expandable plug  120  inserted into the interior of the molded column  5 . In  FIG. 10B , air pressure is supplied via air supply line  154  to the interior of the expandable plug  120 . The air pressure inside the expandable plug  120  causes the sidewall  128  of the expandable plug  120  to radially expand into engagement with the inner surface of the molded column  5 . Once the expandable plug  120  expands into engagement with the inner surface of the molded column  5 , air pressure is supplied via the second air supply line  156  to the interior of the molded column  5  as shown in  FIG. 10C . As shown in  FIG. 10D , the air pressure inside the molded column  5  initially causes the closed end  24  of the mold  20  to bulge outward. The air then infiltrates between the exterior surface of the molded column  5  and the inner surface  28  of the mold  20 , as shown in  FIG. 10E . The infiltration of air between the exterior surface of the molded column  5  and inner surface  28  of the mold  20  causes the sidewall of the mold  20  to expand radially outward and separate or release from the molded column  5  as shown in  FIGS. 10F and 10G . In other words, the air infiltrating between the exterior surface of the molded column  5  and inner surface  28  of the mold  20  breaks the mold  20  free from the molded column  5 . The molded column  5  may then be pulled axially through the open end  26  of the mold  20 . 
     A wide range of air pressures may be used during the column  5  extraction process. In general, increasing the pressure applied to the interior of the column  5  results in faster release of the mold  20  from the exterior surface of the molded column  5  so that the molded column  5  can be extracted sooner. The air pressure applied to the interior of the expandable plug  120  should be sufficient to prevent the ejection of the expandable plug  120  when the interior of the molded column  5  is pressurized and to provide sufficient gripping force to pull the molded column  5  from the mold  20 . While the pressure applied to the expandable plug  120  may be greater than the pressure applied to the interior of the column  5 , such is not necessary. It has been found that an air pressures of about 30 psi for the interior of the expandable plug  120  and 60 psi for the interior of the molded column  5  works well for the most common column  5  sizes. 
     When the mold  20  is properly inflated, the mold  20  will separate from the exterior surface of the molded column  5  allowing the winch  162  to easily remove the molded column  5  from the mold  20 . If the winch  162  is actuated too early, unnecessary stress may be exerted on the mold  20  and the expandable plug  120 . One issue is that pulling on the expandable plug  120  before the mold  20  releases from the exterior surface of the molded column  5  generates a shear which could damage the molded column  5  or the mold  20 . Further, if the pulling force is applied before the molded column  5  is released from the inner surface of the mold  20 , the winch  162  is pulling not just the molded column  5  but is also compressing the end of the mold  20  against the plate  112 . When the molded column  5  finally releases with the inner surface  28  of the mold  20 , the molded part will suddenly lurch forward. Excessive shear forces may also cause damage to the expandable plug  120 . 
     In order to avoid such issues, a separate mold inflation step may be performed prior to the extraction step.  FIGS. 11A-110  illustrate an exemplary inflation step. This inflation step may be performed at the same station where the mold  20  is extracted, or at a separate work station. As shown in  FIG. 11A , the mold  20  with the molded column  5  formed therein is inserted into a holding fixture  210 . The holding fixture  210  includes a backstop  212  and a seal plate  214 . The seal plate  214  is pressed against the open end  26  of the mold  20 . An air tube  218  including a coupling connects to an air supply line  220  to supply air to the interior of the molded column  5 . The air supply line may include a valve  224  for opening and closing the air supply line. When the valve  224  is open, air is applied to the interior of the molded column  5 . In a manner similar to that shown in  FIGS. 10A-10F , the air flows around the ends of the molded column  5  and infiltrates the space between the exterior surface of the molded column  5  and inner surface  28  of the mold  20 .  FIG. 11B . The air infiltration causes the sidewall of the mold  20  to expand radially outward so that the inner surface  28  of the mold  20  releases from the exterior surface of the molded column  5  as shown in  FIG. 110 . After the mold  20  is released from the exterior surface of the molded column  5 , the mold  20  may be inserted into the extraction equipment  100  and the molded column  5  may be extracted as previously described. 
     Another problem that may be encountered during the column  5  extraction process is when debris forms on the interior surface of the molded column  5  preventing the insertion of the expandable plug  120 . In this case, the mold  20  can be inflated as shown in  FIGS. 11A-110  and a gripping tool as shown in  FIGS. 12 and 13  can be used to pull the molded column  5  from the mold  20 . 
       FIG. 12  illustrates an exemplary embodiment of a gripping tool, referred to herein as the firefly  300 . The firefly  300  comprises a shaft  305  having an eyelet  310  at one end thereof, a pair of wing members  330  pivotally connected to the shaft  305 , and a pair of tension springs  380  connected between the shaft at  305  and respective wing members  330  for biasing the wing members  330  to an expanded position. The wing members are configured to expand when pivoted away from the shaft and to retract when pivoted toward the shaft  305 . 
     The wing members  330  are made from a flat steel plate or other suitable material. Mounting brackets  315  are fixedly secured to the shaft  305  to provide a structure for pivotally connecting the wing members  330  to the shaft  305 . The wing members  330  are secured by a nut and bolt arrangement  355  that pass through aligned holes (not shown) in the wing members  330  and mounting brackets  315 . The wing members  330  include a leading edge  335 , a trailing edge  340 , and outer edge  345 . The outer edge  345  of each wing member  330  is configured to engage an inner surface of the molded column  5  and includes a series of serrations or teeth  350 . The outer edge  345  is arcuately shaped so that, moving from the leading edge  335  toward the trailing edge  340 , the outer edge  345  gets increasingly closer to a pivot axis A of the wing member  330 . That is, a first distance D 1  of the outer edge  345  from the pivot axis A at a point adjacent the leading edge  335  of the wing member  330  is greater than a second distance D 2  of the outer edge  345  from the pivot axis at a point adjacent the trailing edge  340  of the wing member  330 . Due to the shape of the wing members  300 , the wing members radially expand when the wing members pivot away from the shaft  305  and retract when the wing members pivot toward the shaft. 
     A tension spring  380  or other biasing member is connected between each wing member  330  and the end of the shaft  305  opposite the eyelet  310  for biasing the wing members  330  towards an open or expanded position. One end of each spring member  380  connects to a loop  320  secured to the end of the shaft  305 , while the opposite end of each spring member  380  connects to a spring hole  360  disposed adjacent a trailing edge  340  of the wing member  330 . As will be apparent, the spring members  380  tend to expand or spread the wing members  330  while allowing the wing members  330  to retract inwardly during insertion of the firefly  300  into the interior of a molded column  5   20 . 
     A release cord  390  is connected to each wing member  330  to aid in releasing tension on the wing members  330  once the extraction of the molded column  5  is complete. The release cords  390  connect at one end to openings  365  adjacent the leading edge  335  of the wing members  330  and pass through guide loops  325  that are fixedly secured to the shaft  305 . 
     In use, the firefly  300  is inserted into the molded column  5  as shown in  FIG. 12 . During insertion of the firefly  300  into the molded column  5 , the wing members  330  will pivot inwardly allowing the firefly  300  to slide into the molded column  5   20 . The tension springs  380  will act to maintain the outer edges  345  of the wing members  330  in contact with the interior surface of the molded column  5   20 . Once the firefly  300  is inserted into the molded column  5   20 , the hook  166  at the end of the cable  164  is engaged with the eyelet  310  of the firefly  300  and the winch  162  is actuated. The cable  164  and hook  166  apply an axial force to the firefly  300  to the molded column  5  from the mold  20 . Due to the geometric arrangement of the firefly  300 , the axial pulling force causes the wing members  330  to firmly grip the interior surface of the molded column  5 . In general, the greater the axial force applied to the firefly  330 , the greater the gripping force will be. Once the column  5  is removed from the mold  20 , the release cords  390  may be pulled to release the tension on the wing members  330  so that the firefly  300  can be removed from the interior of the molded column  5 . 
       FIG. 13  illustrates an exemplary embodiment of a gripping tool, referred to herein as the wedge  400 . The wedge  400  comprises a shaft  405  having an eyelet  410  at one end thereof, a wedge body  415  connected to one end of the shaft  405 , and an expansion member  450 . As explained in more detail below, the wedge body  415  is received in an open cavity  460  in the expansion member  450 . The wedge body  415  and expansion member  450  both include inclined surfaces so that when an axial force is applied to the wedge body  415  via the shaft  405 , the axial movement of the wedge body  415  causes the expansion member  450  to expand and grip the inner surface of the molded column  5 . 
     In one embodiment, the wedge body  415  comprises a tapered cylinder made of a rigid material such as metal, wood, or plastic. The outer surface  420  of the wedge body  415  tapers inward from a distal end (away from the shaft  405 ) towards the proximal end. The shaft  405  is fixedly secured to the proximal end of the wedge body  415 . For example, the shaft  405  may have a threaded end that screws into a threaded opening in the wedge body  415 . 
     The expansion member  450  has a generally cylindrical outer surface  455  and is made of a resilient material, such as natural rubber or silicone rubber, that can deform and return to its original condition. As previously noted, a cavity  460  is formed in the expansion member  450 . The cavity  460  is closed at one end by the bottom wall  470  of the expansion member  450 . The opposite end of the cavity  460  is open to receive the wedge body  415 . The cavity  460  extends axially along a central axis of the expansion member  450  and an inner surface  465  of the expansion member  450  surrounding the cavity  460  tapers inwardly from the distal end towards the proximal end. In one embodiment, the slope of the inner surface  465  of the cavity  460  matches the slope of the outer surface  420  of the wedge body  415 . A bottom wall  465  of the expansion member  450  closes one end of the cavity  460  while the opposite end of the cavity  460  is open to receive the wedge body  415 . The bottom wall  470  includes an opening  475  through which the shaft  405  extends. 
     The expansion member  450  mounts to an end plate  430  made of metal, wood, plastic, or other rigid material. The bottom wall  470  of the expansion member  450  may be secured to one side of the end plate  430  by an adhesive, mechanical fasteners, or other suitable securing means. The end plate  430  includes a tubular sleeve  435  which aligns with the opening  475  in the bottom wall  470  of the expansion member  450 . The shaft  405  passes through the sleeve  435  and the aligned opening  475  in the bottom wall  470  of the expansion member  450 . 
     In use, the wedge  400  is inserted into the molded column  5  as shown in  FIG. 13 . During insertion of the wedge  400  into the molded column  5 , the wedge body  415  is loosely received in the cavity  460  of the expansion member  450  as shown in  FIG. 13 . Once the wedge is inserted into the molded column  5 , the hook  166  and cable  164  of the pulling device  160  is engaged with the eyelet  410  of the wedge  400  and the winch  162  is actuated. The pulling device  160  applies an axial force to the wedge  400  to pull the wedge body  415  into the cavity  455  of the expansion member  450 . As the wedge body  415  is pulled into the cavity  455  of the expansion member  450 , the sidewalls  455  of the expansion member  450  are forced outward to grip the inner surface of the molded column  5 . It may be necessary to hold the expansion member  450  in place until enough gripping force develops to hold the wedge  400  in place. Once the expansion member  450  has gripped the inner surface of the molded column  5 , the continued application of axial force will pull the molded column  5  out of the mold  20 . 
     The present invention may, of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.