Collapsible table formed of injection-molded half sections

Abstract

A system for injection molding a half-section of a collapsible table that includes a pair of interhinged half-sections. The system is provided with a mold whose dimensions are appropriate to the half-section to be molded therein, and a driven carrier adjacent one end of the mold having cautilevered therefrom parallel core rods that project into the mold. When the carrier is driven to cause the core rods to occupy an “in” position in which the rods are fully within the mold and extend the full length thereof, molten plastic is then injected into the mold to submerge the rods therein. When the plastic cures and rigidifies, parallel reinforcing beams are then created about the rods which are integrated with the resultant half-section. When the carder is driven to withdraw the rods from the mold which are now in an “out” position, the reinforcing beams are then hollow and the resistance of the half-section to bending forces is enhanced.

1 . A system for injection molding a half-section of a collapsible table having a pair of interhinged half-sections supported on leg assemblies, tie half-section, being reinforced by hollow parallel beams integral therewith, said system comprising: 
 A. a rectangular mold having a cavity therein whose dimensions and shape are appropriate to the half-section to be molded;    B. a driveable carrier adjacent an end of the mold having parallel core rods cantilevered therefrom which project into the mold, said core rods having positions corresponding to the parallel beams of the half-section, and having substantially the same length and cross-section;    C. drive means to reciprocate the carrier so that in a forward stroke the rods occupy an “in” position filly within the mold, and in a reverse stoke are in an “out” position retraced from the mold; and    D. means to inject molten plastic into the mold when the core rods are in their “in” position to fill the mold and submerges the rods whereby when the plastic curves and rigidifies, there is then produced the beam-reinforced half-section, and when the rods are in their “out” position and the half-section is taken out of the mold its beams are then hollow whereby the resistance of the half-section to flexion forces is enhanced.    
     
     
         2 . A system as set forth in  claim 1 , in which the parallel beams include a pair of border beams extending longitudinally along opposite sides of the half-section, at least one beam being intermediate the border beams.  
     
     
         3 . A system as set forth in  claim 2 , in which between the border beams at spaced positions are a pair of intermediate beam.  
     
     
         4 . A system as set forth in  claim 1 , in which the drive means is constituted by a motorized mechanism.  
     
     
         5 . A system as set forth in  claim 1 , in which the drive means is constituted by hydraulic cylinders.  
     
     
         6 . A system as set forth in  claim 1 , in which the cavity in the mold is provided with rounded corners at an end thereof to create corresponding corners in the half-section.  
     
     
         7 . A system as set forth in  claim 1 , in which the means to inject molded plastic into the mold includes a cylinder having an extruder screw in which pellets of thermoplastic material are melted and are exuded from a nozzle.  
     
     
         8 . A collapsible table including a pair of interhinged half-sections, each half-section being made by the method set forth in  claim 1 .  
     
     
         9 . A collapsible table as set forth in  claim 8 , in which attached to each half-section and hinged thereto is a leg assembly which when the table is collapsed is folded against the table section.  
     
     
         10 . A collapsible table as set forth in  claim 9 , in which each half-section is molded of polyethylene.  
     
     
         11 . A system as set forth in  claim 1 , in which the half-section of the collapsible table is further reinforced by a hollow transverse beam having a channel shape formed at an end of the half-section to resist bending forces which seek to bend the half-section along a transverse axis.  
     
     
         12 . A system as in  claim 11 , in which the transverse beam is formed by a transverse bar disposed in the mold having a projecting nose that is profiled to define said channel-shaped beam.  
     
     
         13 . A system as set forth in  claim 12 , in which the channel-shaped beam includes an inwardly-directed ledge that underlies the nose and prevents tile withdrawal of the molded half-section from the mold.  
     
     
         14 . A system as set forth in  claim 13 , further including means to withdraw the nose of the bar out of and away from tile channel of the transverse beam upon completion of its molding so that the half-section can then be lifted out of the mold.  
     
     
         15 . A system as set forth in  claim 14 , in which is provided a jiggle mechanism to swing the bar out of and away from the channel.