Patent ID: 8141997

Claim:
An ink supply system comprising: a reservoir configured to hold a volume of ink and configured to be in fluid communication with a fluid ejection structure; and a foam regulator operable in a first state in which the foam regulator permits application of negative pressure through the foam regulator to apply negative pressure to the fluid ejection structure and to the reservoir, and a second state in which the foam regulator blocks passage of ink foam through the foam regulator, wherein the foam regulator comprises: a chamber in fluid communication with the reservoir and in fluid communication with a first conduit that is configured to communicate with a negative pressure source; and a buoyant member positioned within the chamber and freely movable, in response to a variable level of ink foam within the chamber, between a first position in which the buoyant member permits application of negative pressure through the chamber in the first state of operation and a second position in which the buoyant member, upon rising in response to a build up of ink foam within the chamber, blocks fluid communication from the chamber into the first conduit in the second state of operation.