Mechanics model and optimum design of PE pellet shell for anti-water-seepage with ease in open

Abstract

Polyethylene capsule shells are a kind of container for pills with low cost and long-term preservation, after paraffin-sealed. This kind of pellet shell is composed of two hemispheric shells with the seal convex and concave allowances, at which they connect, locate and unify together as a whole by local elastic deformation. However, the water seepage occurs in certain percentage of the pills during paraffin-seal operation. In order to solve the problem of water seepage and further improve the process, the current study presents the tension model under the action of ideal gas in paraffin-sealing, the enhanced cantilever beam model under water cooling, and the simply supported beam model for investigation of the cause of the water seepage. The criterion of impervious water was put forward and developed with anti-inference method. The case analysis shows that the seepage is caused by the unreasonable structure of the seal of PE pellet. On the basis of this, the seal allowance of the shell is improved and optimized in the current design. And the overlap amount of the half shells was increased from 0.15mm to 0.30mm, at least, with protruding and half shot shell with concave is increased and the small Angle of the double V structure is adopted. The results of calculation and test show that the new design is of rational and reliability, and it met the requirements of small force and ease in opening the shell.