Patent Publication Number: US-7216842-B2

Title: Pocket former

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to the field of post-tensioning concrete structures, and the methods and apparatus for forming the same. More particularly, the invention relates to a pocket former and methods of forming a pocket surface for assembling a post-tensioning concrete structure. 
   Post-tensioning is a process where high strength cables are embedded in concrete and tensioned after the concrete cures. The residual tension that is retained in the cable increases the tinsel strength of the finished concrete structure. Cable ends are secured within the concrete with specially designed steel anchors. Cable assemblies are pre-manufactured specifically for a given job. The cable assemblies include a complete assembled anchor on the “dead end” and a “free end” that is assembled on the job site. 
   The free end assembly is comprised of a standard anchor to transfer cable tension to the concrete, tapered retainer keys to secure the cable to the anchor, a pocket former to create a void in the concrete where tensioning jacks are attached to the cable, and finally grout to seal the finished assembly. 
   Removal of the pocket former after the concrete has cured is usually done by gripping the plastic ribs and pulling or prying the pocket former out of the pocket. This often causes serious damage to the pocket former making them non-reusable. Additionally, during concrete placement, concrete occasionally leaks between the second rim of the pocket former and the concrete form. This leaked concrete hardens and prevents the removal of the pocket former. 
   Therefore, a principal object of this invention is to provide a pocket former that reduces the incidence of concrete leakage between the second rim of the pocket former and the concrete form. 
   Another object of the invention is to provide an improved method and apparatus for applying removal forces to the pocket former that minimizes damage to the pocket former. 
   A further object of the invention is to provide a pocket former that produces a concrete void or pocket with improved surface geometry to promote adhesion of grout. 
   These and other objects will be apparent to those skilled in the art. 
   BRIEF SUMMARY OF THE INVENTION 
   A pocket former includes an outer barrel having a first rim, a second rim and a frustoconical body portion extending from the first rim to the second rim. A center barrel is connected to the outer barrel and has a proximal lip adjacent the first rim of the outer barrel, a distal lip adjacent the second rim of the outer barrel, and a tubular body portion extending from the proximal lip to the distal lip, and extends beyond both the first rim and the second rim. An annular flange curves out and away from the second rim of the outer barrel. A spiral surface is located on the frustoconical body portion of the outer barrel. A nut surface is located on the tubular body portion of the center barrel adjacent the distal lip. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a pocket former of conventional configuration; 
       FIG. 2  is a sectional side view of the pocket former of conventional configuration taken on line  1 — 1  of  FIG. 1 ; 
       FIG. 3  is a sectional side view of the pocket former of conventional configuration taken on line  2 — 2  of  FIG. 1 ; 
       FIG. 4  is a perspective view of a pocket former of the present invention; 
       FIG. 5  is a sectional side view of the pocket former of the present invention taken on line  5 — 5  of  FIG. 4 ; 
       FIG. 6  is a sectional side view of the pocket former of the present invention taken on line  6 — 6  of  FIG. 4 ; 
       FIG. 7  is a partial cross-sectional view of the pocket former of the present invention as taken across lines  6 — 6  of  FIG. 4  within a concrete substrate; and 
       FIG. 8  shows a partial cross-sectional view of the concrete substrate of  FIG. 7  with the pocket former removed. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIGS. 1–3 , there is shown the conventional prior art pocket former  10 . The conventional pocket former  10  includes a body portion  12  with a tubular member  14  extending therethrough. The body portion  12  has a generally frustoconical configuration. The tubular member  14  extends centrally through the frustoconical configuration of the body portion  12 . The tubular member  14  is generally tapered from end  16  downwardly toward end  18 . The tubular member  14  serves to allow a cable to extend centrally therethrough. Similarly, the body portion  12  is tapered downwardly in the direction toward end  18 . A plurality of struts  20  extend between the tubular member  14  and the inside of the body portion  12 . 
   Unfortunately, the configuration of the pocket former  10  of the prior art does not facilitate the ability to remove the pocket former  10  after concrete has cured. The prior art method of removing the pocket former  10  is usually done by gripping the struts  20  and pulling or prying the pocket former  10  out of the pocket. As noted above, this often causes serious damage to the pocket former  10  making them non-reusable. Additionally, during concrete placement, concrete occasionally leaks between the pocket former  10  and the concrete form. The leaked concrete hardens and prevents the removal of the pocket former  10 . 
   With reference to  FIGS. 5 and 6 , the pocket former  30  of the present invention is shown. The pocket former  30  of the present invention includes an outer barrel  32  having a first rim  34 , a second rim  36  and a frustoconical body portion  38  extending from the first rim  34  to the second rim  36 . 
   A center barrel  42  is positioned centrally within the outer barrel  32  and extends beyond both the first rim  34  and the second rim  36 . The center barrel  42  has a proximal lip  44  adjacent the first rim  34  of the outer barrel  32 ; a distal lip  46  adjacent the second rim  36  of the outer barrel  32 ; and a tubular body portion  48  extending from the proximal lip  44  to the distal lip  46 . The tubular body portion  48  has a central opening  50  therethrough, extending from the proximal lip  44  to the distal lip  46 . The tubular body portion  48  is generally tapered near the proximal lip  44 . The central opening  50  serves to allow a cable (not shown) to extend centrally therethrough. 
   An annular shoulder  52  connects the first rim  34  of the outer barrel  32  to the tubular body portion  48  of the center barrel  42 . The annular shoulder  52  is oriented to be generally perpendicular to the longitudinal axis of both the outer barrel  32  and the center barrel  32 . A plurality of cross ribs  54  extend between the tubular body portion  48  of the center barrel  42  and the frustoconical body portion  38  of the outer barrel  32 . The cross ribs  54  are oriented to extend radially from the longitudinal axis of both the outer barrel  32  and the center barrel  32 . An annular ridge  56  is positioned adjacent the first rim  34  of the outer barrel  32  on the annular shoulder  52 , and extends outwardly from the annular shoulder  52  in the direction of the proximal lip  44  of the center barrel  42 . The center barrel  42  and the outer barrel  42  are integrally formed together. 
   A spiral surface  58  is provided on the frustoconical body portion  38  of outer barrel  32 . The spiral surface  58  is formed as threads or a spiral shape molded on the outer surface of the outer barrel  32 . The spiral surface  58  provides improved mechanical properties for removing the pocket former  30  from the concrete. The operator can remove the pocket former  30  with a rotating motion instead of a pulling motion. With the rotating motion, the spiral surface  58  substantially improves the mechanical advantage a person can exert upon the pocket former  30  in much the same way that a screw jack can be used to lift a heavy load. Thus, this feature of the spiral surface  58  substantially reduces the damage to the pocket former  30  improving its reusability, and reduces operator fatigue and the potential for injury. 
   A nut surface  60  is provided on the tubular body portion  48  of the center barrel  42 , adjacent the distal lip  46 . The nut surface  60  is formed of any desired geometry, such as hexagonal, square, or the like. The nut surface  60 , as shown has a tapered hexagonal shape that provides a convenient surface for applying rotational force on the pocket former  30  by a standard hand tool such as a wrench, pliers or the like. Additionally, the hexagonal shape of the nut surface  60  further strengthens the pocket former  30  improving its reusability after removal. 
   Additionally, as the provision of nut surface  60  allows the application of rotational force to the center barrel  42  of the pocket former  30 , this results in the center barrel  42  rotating its position relative to the outer barrel  32 . In this condition, the ribs  54  that attach the center barrel  42  to the outer barrel  32  foreshorten thereby pulling the outer barrel  32  inward and away from the surrounding concrete. This reduction in the diameter of the outer barrel  32  further reduces the work energy required to remove the pocket former  30 . 
   An annular flange  62  curves out and away from the second rim  36  of the outer barrel  32 . The annular flange  62  is integrally molded on the outer rim of the pocket former and compensates for surface irregularities of the concrete form and any misalignments caused by improper installation. The annular flange  62  forms a seal or gasket between the concrete substrate and the concrete form. This seal reduces the incidence of concrete leakage thereby improving the likelihood the pocket former  30  can be removed without damage. That reduction of concrete leakage eliminates the labor costs associated with chiseling or removal of this concrete prior to pocket former  30  removal. 
   It will be understood that while the embodiment described above included all three features of the integral seal or gasket, the tapered hexagonal shape, and the thread or spiral surface; a pocket former of the present invention will include one of these features alone or in any combination thereof. 
   With reference to  FIG. 7 , in use, the pocket former  30  is connected to a free anchor  66 . As shown, the annular ridge  56  is fitted to a collar  68  of the free anchor  66 . Alternatively, the pocket former  30  is sized to fit on the outside of the collar  68  of the free anchor  66 . 
   Placed adjacent to the distal lip  46  is a concrete form  70 . The concrete form  70  has an opening  72  through which a portion of the center barrel  42  extends. When assembled, the center barrel  42  of the pocket former  30  is received within an opening  72  in the concrete form  70 . The concrete form  70  presses against the annular flange  62  on the outer barrel  32  to form a seal. The concrete is then poured within the concrete form  70  between the concrete forms  70  and over the pocket former  30  to form a concrete substrate  74  about the outer barrel  32  and annular flange  62  of the pocket former  30 . As noted above, the annular flange  62  forms a seal or gasket between the concrete substrate  74  and the concrete form  70 , preventing leakage of concrete between the pocket former  30  and the concrete form  70  and into opening  72 . 
   Once the concrete substrate  74  is cured, the concrete form  70  is removed, providing access to the pocket former  30 . As noted above, removal of the pocket former  30  is facilitated by the application of rotational force on the nut surface  60  of the pocket former  30  by a standard hand tool. This rotation results in the center barrel  42  rotating its position relative to the outer barrel  32  with the ribs  54  pulling the outer barrel  32  inward and away from the surrounding concrete. Additionally, with the rotating motion, the spiral surface  58  substantially improves the mechanical advantage a person can exert upon the interface between the concrete substrate  74  and the pocket former  30 . 
   With reference to  FIG. 8 , once the pocket former  30  has been removed, the concrete substrate  74  includes an outer edge  76  formed at the interface of the annular flange  62  and the concrete form  70 . A pocket surface  78  extends from the outer edge  76  inwardly toward the free anchor  66 . The pocket surface  78  has a spiral shape formed from its contact with the spiral surface  58  of the pocket former  30 . The pocket surface improves the adhesion of sealing grout, as the angular surfaces created by the spiral surface  58  provide a mechanical lock between the concrete and the grout. Further, these angular surfaces created by the spiral surface  58  provide added surface area which further prevents water, salts and other corrosives from entering the anchor area and corroding and weakening the anchor  66 . 
   It will be appreciated by those skilled in the art that other various modifications could be made to the device without departing from the spirit in scope of this invention. All such modifications and changes fall within the scope of the claims and are intended to be covered thereby.