Method and apparatus for forming a formwork for a concrete slab

Abstract

A method and apparatus for forming a formwork for a ribbed or waffle concrete slab is provided. The apparatus includes a rectangular block having a ledge around the base, the ledge having a dimension of half the desired width of the base ribs of the concrete slab, and a keystone connector. The keystone connector has an engagement portion configured to attach to an engagement portion on each block. In a method, the blocks are laid out so that the ledges of adjacent blocks are in contact. A keystone connector is then placed at each intersection of four blocks by attaching the respective engagement portions of the keystone connector and each block so that the keystone connector holds each of the four blocks in place relative to one another. The keystone connector is also configured to retain a reinforcing rod laid in the channel between adjacent blocks.

1 . A method of forming a formwork that is configured to form a ribbed or waffle concrete slab using a hollow block and a keystone connector, comprising:
 placing the hollow block on a site where the slab is to be formed; and   fitting the keystone connector to the hollow block, wherein   the keystone connector and the hollow block are configured to non-releasably lock onto one another when fitted together.   
     
     
         2 . A method as claimed in  claim 1 , wherein
 a plurality of hollow blocks are used, each hollow block having a top, four sides, and a ledge extending from each side of the respective hollow block along an edge of the respective hollow block distal to the top of the hollow block, the ledge forming a base for the respective hollow block, and   the method further comprises:
 placing the plurality of hollow blocks adjacent one another on the site where the slab is to be formed; and 
 fitting a keystone connector to each hollow block at an intersection of four adjacent hollow blocks, wherein 
   the keystone connector is configured to non-releasably lock onto each of the four hollow blocks at the intersection and to fix them in place relative to one another.   
     
     
         3 . A method as claimed in  claim 2  wherein the step of placing the hollow blocks adjacent one another further comprises:
 placing at least a portion of an edge of a ledge of one hollow block in contact with at least a portion of an edge of a ledge of an adjacent hollow block. 
 
     
     
         4 . A method as claimed in  claim 2 , further comprising:
 placing a reinforcing rod into a space between the adjacent hollow blocks such that the reinforcing rod is retained by the keystone connector at the intersection.   
     
     
         5 . A method as claimed in  claim 1 , wherein
 the keystone connector comprises a keystone engagement portion having a resilient barb on a pin and the hollow block comprises a block engagement portion comprising an aperture having a lateral dimension less than a lateral dimension of the pin and resilient barb together, the aperture located in the vicinity of a corner of the hollow block near the base, and   the step of fitting the keystone connector further comprises:
 pushing the pin of the engagement portion of the keystone connector into the aperture in the hollow block engagement portion such that the resilient barb deforms on entry into the aperture and returns to its original form when the keystone engagement portion is fully engaged with the aperture. 
   
     
     
         6 . A formwork for a ribbed or waffle concrete slab, comprising:
 a hollow block having a top and four sides;   a ledge extending from each side of the hollow block along an edge of the hollow block distal to the top of the hollow block, the ledge forming a base for the hollow block; and   a keystone connector, wherein   the keystone connector and the hollow block are configured to non-releasably lock onto one another.   
     
     
         7 . A formwork as claimed in  claim 6 , wherein
 four hollow blocks are arranged adjacent one another on a site where the slab is to be formed, the four hollow blocks meeting at an intersection,   the keystone connector is located at the intersection, and   the keystone connector is configured to non-releasably lock onto each of the four hollow blocks at the intersection and to fix them in place relative to one another.   
     
     
         8 . A formwork as claimed in  claim 7 , wherein the keystone connector comprises four engagement portions, each engagement portion configured to lock onto a block engagement portion of one or other of the four hollow blocks at an intersection and to fix them in place relative to one another. 
     
     
         9 . A formwork as claimed in  claim 8 , wherein the keystone engagement portion comprises a pin with a resilient barb in the vicinity of an end of the pin, the resilient barb configured to deform when the keystone engagement portion is pushed into the block engagement portion and to return to its original shape when the keystone engagement portion is fully locked onto the block engagement portion. 
     
     
         10 . A formwork as claimed in  claim 6 , wherein
 the keystone connector comprises two pairs of retaining portions configured to retain a reinforcing bar,   one of the pairs of retaining portions is oriented orthogonally to the other pair of retaining portions, and   the retaining portions are oriented to retain a reinforcing bar placed into a space between two adjacent hollow blocks.   
     
     
         11 . A formwork as claimed in  claim 10 , wherein the retaining portion comprises a guide portion configured to guide a reinforcing rod into a groove of the retaining portion and a retainer in the form of a pair of resilient barbs located at an entry to the guide portion, the barbs configured to deform to allow a reinforcing rod to enter the guide portion and to revert to their original shape after the reinforcing rod is passed the barbs, thus retaining the reinforcing bar in the retaining portion. 
     
     
         12 . A formwork as claimed in  claim 6 , wherein the keystone is configured to fix the hollow blocks at an intersection such that at least a portion of the ledge of each hollow block at the intersection is in contact with at least a portion of an edge of the ledge of an adjacent hollow block at the intersection. 
     
     
         13 . A formwork as claimed in  claim 6 , wherein the hollow block comprises a block engagement portion configured to lock onto a keystone engagement portion of a keystone connector. 
     
     
         14 . A formwork as claimed in  claim 13 , wherein the engagement portion of the keystone connector comprises a pin with a resilient barb and the block engagement portion includes an aperture in the hollow block, the resilient barb configured to deform when the pin is pushed into the aperture and to return to its original shape when the barb is locked onto the aperture. 
     
     
         15 . A formwork as claimed in  claim 6 , wherein the hollow block comprises indentations that form two arches oriented orthogonally to one another. 
     
     
         16 . A keystone connector, comprising:
 a pin having a resilient barb at an end of the pin, wherein   the keystone connector is configured for use as a component of a formwork for a waffle or ribbed concrete slab.   
     
     
         17 . A keystone connector as claimed in  claim 16 , further comprising:
 a retaining portion configured to retain a reinforcing bar.   
     
     
         18 . A hollow block configured for use as a component of a formwork for a waffle or ribbed concrete slab, comprising:
 a top and four sides;   an aperture located at a corner of the hollow block; and   a ledge extending from each side of the hollow block along an edge of the hollow block distal to the top of the hollow block, the ledge forming a base for the hollow block.   
     
     
         19 . A hollow block as claimed in  claim 18 , further comprising:
 indentations that form two arches oriented orthogonally to one another.