Probe and syringe drive apparatus

In automatic dispensing apparatus for sequentially transferring liquids from a plurality of sample containers having different sample levels to respective analysis containers, including a pipet probe assembly having an elongated pipet probe, probe drive means for inserting said pipet probe into said sample and moving said pipet probe assembly between said sample containers and said analysis containers, aspirating means for aspirating a respective sample into said probe, and dispensing means for dispensing the aspirated sample into said respective analysis containers, the improvement comprising:

• said pipet probe having a beveled tip with the angle of said bevel being about 25.degree.-35.degree. with respect to the longitudinal axis of said tip:
• an elongated level sensing probe mounted to and extending downwardly from said pipet probe assembly, said level sensing probe including a needle-like tip extending adjacent said pipet probe;
• said pipet probe tip extending slightly below said needle-like tip a distance defining the amount of minimal penetration of said pipet probe tip below a respective sample level;
• syringe means including a syringe fluidly coupled to said pipet probe,
• said syringe means including for aspirating a small amount of air into said pipet probe upon signalled movement of said probe assembly towards said sample containers said immediately prior to said pipet probe tip entering said sample to prevent dilution of said sample;
• and control means coupled intermediate said syringe means, said level sensing probe and said probe drive means, for signalling said movement of said probe assembly towards said sample container and responding to said needle-like tip contacting the level of a respective sample to stop said probe drive means to minimize the penetration of said pipet probe tip below the level of said respective sample.