Container with crack-resistant rim

Abstract

A plastic container comprises a bottom wall, a side wall extending upwardly and laterally outwardly from the bottom wall, and an undulating rim extending laterally outwardly from an upper portion of the side wall. The undulating rim forms a plurality of waves extending at least partially around the upper portion of the side wall. Each wave forms a crest and a trough that are generally perpendicular to an adjacent section of the upper portion of the side wall. In response to exerting a tensile load on the rim, the undulating rim acts like an accordion or spring and effectively increases the perimeter along an outer trimmed edge of the rim. In particular, the waves allow the rim to flatten, thereby reducing the hoop stress generated by the tensile load. By relieving the hoop stress on the outer trimmed edge of the rim, the tendency of the rim to crack or break is minimized.

What is claimed is:  
     
         1 . A plastic container comprising: 
 a bottom wall;    a side wall extending upwardly and laterally outwardly from the bottom wall; and    an undulating rim extending laterally outwardly from an upper portion of the side wall, the undulating rim forming a plurality of waves extending at least partially around the upper portion of the side wall, each wave forming a crest and a trough.    
     
     
         2 . The container of    claim 1   , wherein the container is generally round.  
     
     
         3 . The container of    claim 2   , wherein the waves occupy an entire circumference of the container.  
     
     
         4 . The container of    claim 2   , wherein each wave occupies a circumferential angle ranging from about 2 degrees to about 8 degrees.  
     
     
         5 . The container of    claim 1   , wherein the waves occupy an entire perimeter of the container.  
     
     
         6 . The container of    claim 1   , wherein each wave has a wavelength λ and a segment length L equal to a distance along a surface of the wave between its crest and its trough, and wherein the ratio 2L/λ ranges from about 2 percent to about 8 percent.  
     
     
         7 . The container of    claim 1   , wherein the crest and the trough of each wave are generally perpendicular to an adjacent section of the upper portion of the side wall.  
     
     
         8 . The container of    claim 1   , wherein the container is a plate.  
     
     
         9 . The container of    claim 1   , wherein each wave has a wavelength λ less than or equal to about 0.75 inches.