Pump and metering device

A pump and metering apparatus for supplying a controlled amount of a volatile liquid from a liquid supply source to a utilization device, comprising:

• a chamber for receiving volatile liquid from a liquid supply source;
• a piston within the chamber movable in a first direction for drawing liquid from the liquid supply source to the chamber and movable in a second direction for dispensing liquid from the chamber;
• means for moving the piston in the first and second directions;
• a reservoir for storing the liquid dispensed from the chamber;
• means operable between a closed position in response to movement of the piston in the first direction to prevent dispensement of liquid from the chamber, and an open position in response to movement of the piston in the second direction to dispense liquid from the chamber to the reservoir;
• metering means for controlling the rate of flow of liquid from the reservoir to the utilization device;
• a tube extending from the reservoir to the utilization device having one end thereof attached to the metering means for receiving drops of liquid dispensed therefrom, the other end of the tube attached to inlet means of the utilizaton device and a formed portion intermediate the said ends of the tube for storing a quantity of volatile liquid in which the volatile liquid exists as both liquid and gas, said one end of the tube positioned above the level of the other end of the tube to maintain the amount of liquid flow to the utilization device equal to the amount of liquid flow from the reservoir;
• a first vent means to equilibrate the atmosphere in the tube by allowing the gas to re-enter the reservoir;
• and
• a second vent means to equilibrate the reservoir to the atmosphere to prevent impediment to liquid flow.