Patent Application
20060033003
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.
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
Referring to
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
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
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
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.
