Scotch-Yoke mechanism for a syringe pump - A case study

Abstract

Syringe Pump is mainly used in microfluidics, where precise flow rate is required. Precise flow rate is achieved by using minimum torque and at low speed, for such requirements a mechanism has to be constructed. The input is from a stepper motor, so a rotary to linear motion converting mechanism is required, which will work efficiently on such low torque applications. This work mainly looks into feasibility of scotch yoke rather than conventionally used crank and slider mechanism. Scotch yoke is a rotary to linear conversion mechanism. It contains mainly two parts i) a rolling scotch and ii) a sliding yoke. The yoke is driven by a pin eccentrically placed on the scotch. Since proximity of the mechanism is nearer to the source, the loss accounted is less in the case of scotch yoke. In this work both crank-slider and scotch-yoke are examined through simulation using MSC ADAMS software and the maximum velocity of that can be achieved is obtained analytically through Kinematic analysis of scotch-yoke mechanism.