A medical pump includes a chassis having a fixed seat and a carriage having a footing for receiving a fluid delivery device and restricting its movement. An actuator assembly is provided that allows for moving the carriage between an opened and closed position to engage the fluid delivery device to the seat. A rack and pinion system is utilized in combination with a cam element and spring element to provide a bi-stable actuator assembly that urges the carriage into a fully opened position or a fully closed position and will not allow the carriage to dwell in an intermediate position if external force is withdrawn.
