Form and method and apparatus for making a form

Abstract

A concrete form having a tubular body formed from a flexile strip wound helically in successive passes to define a wall of the form. The adjacent edges of the strip being releasably engaged with one another to exhibit axial separation of the strip.

1 . A concrete form having a tubular body formed from a flexile strip wound helically in successive passes to define a wall of said form, adjacent edges of said strip being releasably engaged with one another to inhibit axial separation of said strip. 
     
     
         2 . A concrete form according to  claim 1  wherein said adjacent edges are inter-engaged by a groove formed on one edge of said strip and a tongue foiled on an opposite edge of said strip. 
     
     
         3 . A concrete form according to  claim 2  wherein said tongue and groove have complementary re-entrant formations to inhibit radial separation of said tongue from said groove. 
     
     
         4 . A form according to  claim 2  wherein a locking spline is inserted into said tongue to inhibit axial separation of said tongue and said groove. 
     
     
         5 . A form according to  claim 4  wherein said tongue and groove have complementary re-entrant formations to inhibit radial separation of said tongue from said groove. 
     
     
         6 . A form according to  claim 1  wherein a groove is provided intermediate said edges to receive a tongue projecting from an adjacent overlying strip. 
     
     
         7 . A form according to  claim 1  wherein an open channel is provided on an external surface of said strip to receive a bracket. 
     
     
         8 . A form according to  claim 1  wherein said strip is formed from a plastics material. 
     
     
         9 . A form according to  claim 8  wherein said strip has hollow cells formed therein between external walls of said strip. 
     
     
         10 . A form according to  claim 9  wherein said tongue and groove have complementary re-entrant formations to inhibit separation of adjacent edges of said strip. 
     
     
         11 . A method of forming tubular form from a strip of material having tongue and a groove formed on one edge and a tongue formed on an opposite edge, said method comprising the steps of helically winding said strip to bring adjacent edges into abutment and engaging said tongue with said groove to inhibit axial separation of adjacent edges. 
     
     
         12 . A method according to  claim 11  including the step of inserting a locking spline into said tongue. 
     
     
         13 . A method according to  claim 11  including the step of juxtaposing a pair of strips to provide a pair of layers and inter-engaging said layers to inhibit radial separation. 
     
     
         14 . A strip for use in forming a tubular form, said strip having a body of flexible material, a tongue formed on one edge of said body, a groove on an opposite edge of said body, said tongue and groove having complementary cross sections to permit inter-engagement of said tongue and groove to inhibit axial separation. 
     
     
         15 . A strip according to  claim 14  wherein said tongue and groove have complementary reentrant formations. 
     
     
         16 . A strip according to  claim 14  wherein said tongue has a slot to receive a locking spline. 
     
     
         17 . A strip according to  claim 16  wherein said tongue and groove have complementary re-entrant formations. 
     
     
         18 . A strip according to  claim 11  including an auxiliary groove formed intermediate said edges or one surface of said body. 
     
     
         19 . A strip according to  claim 18  wherein said auxiliary groove has a re-entrant formation. 
     
     
         20 . A strip according to  claim 11  including an auxiliary tongue projecting from said body intermediate said edges. 
     
     
         21 . A strip according to  claim 20  wherein said auxiliary tongue has a re-entrant formation.