Analysis of a Pneumatically Coupled Cam-Actuated Mechanism

Cam-actuated mechanism with a pneumtic coupling is a design improvement upon the conventional system. Pneumatic dashpots are used which provide a cushioning effect, thus reducing the wear and tear of system components. This paper investigates the dynamic behavior of such a system based on a lumped parameter model with a damping factor which is a nonlinear function of the frequency. A digital computer is used as a design tool to determine the effect on the performance of changing design parameters. It is found that the system amplitude ratio peak depends largely upon the pneumatic damper orifice area and that a proper selection of the orifice area will yield a minimum resonance amplitude ratio. I Introduction Numerous instances occur in today's modern industry which call for the use of pneumatic dashpots generally to prevent wear and tear of vital machine components which are under heavy cyclic loading. A cam-actuated mechanism employing pneumatic dashpots is shown in The objective of this paper is to study the effect of changing orifice area on the system damping factor, as well as on the maximum amplitude ratio. The influence of the damper effective stroke on the selection of the orifice area is also reported. II Derivation of Equations Referring to Taking the Laplace transform and rearranging the terms gives the following transfer function: Let 7 = T[ w" and 0 = co/co n , the system amplitude ratio M is obtained by replacing s by jo> in equation / Vol. 103, SEPTEMBER 1981 Transactions of the ASM