Radiation crosslinked polyethylene hinge

Abstract

Polyethylene living hinges used in “snap top” lids for condiments and the like may be electron bean irradiated to partially crosslink the polyethylene to produce a hinge having an improvement in the number of opening and closing cycles until failure of not less than 30%. The irradiated lids may be used in place of polypropylene lids for condiment containers.

1 .- 23 . (canceled) 
     
     
         24 . A device for determining the flexing life of a thinned or creased region in a molded polyethylene part comprising in cooperating arrangement:
 a) a plate comprising a trailing edge, two parallel sides, and a body having a rounded leading edge said body containing one or more means for fixing said part to the body which allow the polyethylene part to be fixed to the body so that the thinned region or crease of the polyethylene part is aligned with the rounded leading edge, a top bar mounded between rotatable plates adjacent the rounded leading edge to hold the thinned region of the thinned part in close contact with the rounded edge;   b) two rotatable discs in cooperating parallel arrangement attached to each side of the plate proximate the rounded edge, connected to each other through a central bar beneath and proximate to said rounded edge at center holes in their foci about which the discs rotate;   c) two parallel contact bars attached at each end through holes spaced within 2 to 10 mm of the perimeter of each disc said contact bars being rotatable above and below said rounded edge so as to engage the part in a fashion that allows bending of the thinned region or crease about said rounded edge during rotation;   d) a pair of cylinders attached legs at opposite sides of plate and also connected through holes offset by from 1 to 5 cm from the respective center hole to each discs;   e) a pair of cam pins that protrude from the exterior face of each disc respectively, located in a position that is on the same radius but angularly offset relative to each other;   f) a pair of sequencing valves on each on leg;   g) a direction valve controlling the flow of fluid to the pneumatic cylinders which reverses the flow of fluid to the pneumatic cylinders when a trigger switch is contacted with a trigger pin; and   h) a counter to count the number of bending cycles the part has completed.   
     
     
         25 . A method for determining the flexing life of a thinned or creased region in a molded polyethylene part comprising in cooperating arrangement:
 a) providing a plate comprising a trailing edge, two parallel sides, and a body having a rounded leading edge said body containing one or more means for fixing said part to the body which allow the polyethylene part to be fixed to the body so that the thinned region or crease of the polyethylene part is aligned with the rounded leading edge, a top bar mounded between rotatable plates adjacent the rounded leading edge to hold the thinned region of the thinned part in close contact with the rounded edge;   b) providing two rotatable discs in cooperating parallel arrangement attached to each side of the plate proximate the rounded edge, connected to each other through a central bar