Cam-driven flow system for use with analytical instruments

In a cam driven liquid transport system of the type for use with an analytical instrument having a liquid sample receiving means and a liquid transport system for selectively drawing liquid from the sample receiving means and into the liquid transport system for transporting the liquid therefrom, the liquid transport system including a pump having a pump chamber with an inlet port and an outlet port, a pump piston in the chamber and adapted for expanding and contracting the chamber, a first transfer conduit having one end coupled to the inlet port and an opposite, inlet end positioned for drawing liquid from the sample receiving means, a second transfer conduit having one end coupled to the outlet port and an opposite end adapted for discharging the liquid, and a valve system in line with the second conduit and selectively movable between variable opened and closed positions, an improvement comprising:

• a rotatably driven power shaft;
• a plurality of eccentric cams mounted along the power shaft;
• a cam follower operatively coupled to each cam, a first of said cam and cam follower combinations in communication with the liquid sample receiving means for selectively placing the liquid sample receiving means in and out of communication with the inlet end of the first transfer conduit, and a second of said cam and cam follower combinations in communication with said pump for driving the piston and selectively expanding and contracting the pump chamber;
• and
• a sensor in association with the power shaft for indicating the rotational position thereof, such that the liquid sample receiving means, the pump and the valve system cooperate to produce a constant liquid flow rate in the liquid transport system.