Patent Publication Number: US-2012042605-A1

Title: Removable Support Cage For Top Of Drilled Pier

Description:
FIELD OF THE INVENTION 
     The present invention relates to a frame for sustaining the cylindrical shape of a flexible enclosure to properly form and contain the upper portion of a concrete pier. 
     BACKGROUND OF THE INVENTION 
     A drilled concrete pier (caisson) is a deep foundation system that is constructed by placing fresh concrete and reinforcing steel into a drilled shaft that transfers a load from the surface to a deep soil mass. The shaft is constructed by rotary methods using either a self-contained drill unit or a crane mounted drill unit. The hole is advanced through soil or rock to the desired bearing stratum. The top one to two feet of the hole near earth grade is usually flared. Following placement of the reinforcing steel into the hole, the hole is filled with concrete and, unless special measures are taken, the top of the pier will conform to the flared portion of the hole, forming a mushroom shaped top on the pier. Among other problems, the mushroom shaped top on the pier increases the area against which uplift pressures are asserted on the caisson by expansive soils. 
     To preclude the formation of mushroom tops on concrete piers flexible retainers are shaped into substantially cylindrical forms and inserted into the hole and placed on top of the wet concrete that has been poured to a level of twelve to twenty four inches below the anticipated top elevation of the pier and a few inches below the point at which the excavation becomes flared. The object of the flexible retainer is to emulate the cylindrical shape of the poured pier, even though the retainer is, in at least one of its embodiments, constructed from an endless loop of corrugated plastic material having spaced apart scoring lines that, when expanded, creates a closed, flexible polygon having a plurality of flat chords (or sides) which forms a “substantially cylindrical” form or enclosure. 
     As concrete is poured into the form it becomes necessary to brace or otherwise hold the form to its “cylindrical” shape by supporting one or more sides of the form against the pressure of the concrete being poured into the form to prevent displacement from its aligned position with the axis of the pier. In addition, as the concrete fills the flexible form the exterior of the form must be backfilled with loose soil in order to provide opposing pressure to the outward pressure of the wet concrete. Filling the form too quickly or failure to provide lateral support with backfill material will result in a misshapen top for the pier. In some cases the form can move completely out of its proper position on the pier. 
     Accordingly, it is the primary purpose of the present invention to provide a removable frame, or cage, which can be inserted into the interior of the flexible form that will maintain its desired shape during the pouring of concrete into the form without the need for any external holding, supporting or backfilling. 
     Another object of the invention is to provide the supporting frame with means allowing the cage frame to be removed from the cylindrical form immediately following the pouring of concrete into the form. 
     Other and further features, advantages and objectives of the present invention will become apparent upon a reading of the following detailed description of the invention taken in conjunction with the accompanying drawings. 
     SUMMARY OF THE INVENTION 
     The removable cage frame of the present invention comprises a split circular ring having upstanding handles and a plurality of circumferentially spaced apart rigid rods that depend from the split ring. The split ring and depending rods are placed into the interior of a flexible polygonal shaped concrete sleeve form to stabilize the sides thereof and insure that concrete poured into the form will be shaped into a substantially cylindrical extension of the pier on top of which the form and the frame are disposed. By exerting upward pressure on the handles, the frame may be removed following pouring of concrete into the form. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic perspective cross section of that portion of the earth into which a hole has been dug and filled with concrete to form a pier (caisson) on the top of which is shown a flexible polygonal form into which concrete is poured to form a substantially cylindrical top for the pier. 
         FIG. 2  is a perspective view of the frame cage of the present invention. 
         FIG. 3  is a perspective view of the frame cage as it would appear as partially removed from the form sleeve following pouring of the concrete. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
       FIG. 1  illustrates the environment in which the cage frame of the present invention is intended to operate. A concrete pier  5  is poured into a hole  8  that has been drilled into the earth  10 . During the drilling operation parts of the periphery of the hole are broken away to form a flared portion  12  having inclined slope sides at the top of the hole  8 . Positioned on the top of the uncured concrete pier  5  is a substantially cylindrical sleeve form  15  having a somewhat smaller diameter than that of the concrete pier. For example, if the pier was twenty four inches in diameter the sleeve form would preferably be approximately twenty two inches in diameter. In this specification and appended claims when the concrete sleeve form is characterized as substantially circular or substantially cylindrical it means that the form is of a polygonal shape whose straight sides form the chords of a circle and which are small enough that the closed plane figure bounded by the straight sides substantially resembles a circle or cylinder. The sleeve form  15  is constructed from an endless loop of corrugated plastic material having a plurality of longitudinal scores that define the sides or the chords forming the polygon. 
     The cage frame  20  of the present invention, as shown in  FIG. 2 , comprises a metal split ring  24  having a plurality of circumferentially spaced apart legs  28  each of whose proximal ends are secured by welding or similar means to the split ring  24 . The length of the legs is equal to or very similar to the longitudinal length L of the sleeve form  15 . The diameter of the ring  24  is slightly smaller, but very close to the diameter of the sleeve form  15 . Prior to inserting the legs  28  into the sleeve form  15 , the legs  28   a  and  28   b , which occupy proximal positions to either side of the open space  36  in the ring, are manually squeezed together to reduce the diameter of the ring by a small amount. Reducing the ring diameter simplifies the insertion of the legs  28  into the interior of the sleeve form  15 . Once the legs are fully inserted into the sleeve form the squeezing pressure on the legs  28   a  and  28   b  is released and the ring springs back to its normal shape and diameter causing the legs  28  to bear with pressure against the interior sides of the polygonal sleeve form  15 . After wet concrete fills the sleeve form  15 , the cage frame  20  is pulled out of the form by exerting upward force on the handles  40  that are attached to opposing sides of the ring and extend upwardly in a direction opposite to that of the legs  28 . 
     The process of using the cage frame of the present invention to complete the upward extension of a drilled pier begins with compressing the diameter of the cage ring by squeezing together the legs of the ring that depend from the extremities of the space  36  in the ring. Having shaped a sleeve form  15  into a substantial cylinder the depending legs of the cage frame are inserted into the interior of the form. When the legs of the frame are inserted their full length into the form compression of the ring is released, allowing the ring to expand to its normal diameter and causing the depending legs of the ring to bring radially outward pressure against the sides of the sleeve form, creating a rigid closed plane polygon figure. 
     The expanded sleeve form is then placed on top of the poured wet concrete that forms the pier. The top of the poured pier is preferably one to two inches below the level of the hole where the flare  12  begins. The lower perimeter of the expanded sleeve form is positioned on the surface of the wet concrete at the top of the poured pier but should not be knifed down into the concrete. After the sleeve form is centered on the top of the poured pier the form can be filled with concrete to the desired level, either the ground surface grade or several inches above ground grade. After the concrete is poured to the appropriate level the cage frame is lifted out of the sleeve form by using the handles  40 . The cage  20  is then cleaned for another similar use. Because the sleeve form was rigidly supported by the cage frame during pouring of concrete into the form, backfilling with soil or maintaining other lateral support for the form was not required in order to create a substantially cylindrical pier extension that is aligned with the pier.