Patent ID: 8225968

Claim:
A pump adapted for coupling in a first fluid circuit between a source of coating material and a dispensing device, the pump including an operating member which extends through a pump housing and adjacent the first fluid circuit, the operating member passing adjacent the first fluid circuit, the passage of the operating member adjacent the first fluid circuit including a seal system to permit operation of the pump while reducing the likelihood of leakage of the coating material from the first fluid circuit out of the housing along the operating member, the seal system including at least first and second seals defining between them a seal chamber facing a pump chamber containing the coating material being pumped, and a second fluid circuit through which a fluid medium is provided under pressure to the seal chamber, the first seal including a rearward face and the second seal including opposed lips defining between them a groove, the lips of the second seal and the rearward face of the first seal defining between them the seal chamber, a first lip of the second seal being sufficiently flexible to permit the fluid medium to be introduced past the first lip of the second seal into the seal chamber.