Back pressure adjustment apparatus for liquid ejection head

A back pressure adjustment apparatus for a liquid ejection head, the back pressure adjustment apparatus comprising:

• a container having a liquid accommodating chamber which is connected to the liquid ejection head and accommodates liquid to be supplied to the liquid ejection head, and a gas accommodating chamber which accommodates gas;
• a movable film which separates the liquid accommodating chamber and the gas accommodating chamber, and forms a portion of whole walls of the liquid accommodating chamber;
• and
• a pressure adjustment pump which is connected to the as accommodating chamber and causes the movable film to deform in such a manner that volume of the gas accommodating chamber is changed, so as to adjust pressure of the liquid accommodated in the liquid accommodating chamber, wherein:
• the movable film has a quadrangle shape having a longer edge and a shorter edge, and has a perimeter edge portion which is affixed to the container, and a central portion which is joined to the perimeter edge portion;
• and
• the perimeter edge portion is divided into a region lying along the longer edge and a region lying along the shorter edge, the region lying along the shorter edge being more liable to deform than the region lying along the longer edge.

A back pressure adjustment apparatus for a liquid ejection head, the back pressure adjustment apparatus comprising:

• a container having a liquid accommodating chamber which is connected to the liquid ejection head and accommodates liquid to be supplied to the liquid ejection head, and a gas accommodating chamber which accommodates gas;
• a movable film which separates the liquid accommodating chamber and the gas accommodating chamber, and forms a portion of whole walls of the liquid accommodating chamber;
• and
• a pressure adjustment pump which is connected to the gas accommodating chamber and causes the movable film to deform in such a manner that volume of the gas accommodating chamber is changed, so as to adjust pressure of the liquid accommodated in the liquid accommodating chamber, wherein
• the movable film has a perimeter edge portion which is affixed to the container, and a central portion which is joined to the perimeter edge portion;
• and
• the perimeter edge portion has a lower rigidity than the central portion, wherein the perimeter edge portion and the central portion of the movable film are made of a same elastic material, and the central portion is thicker than the perimeter edge portion in such a manner that rigidity of the perimeter edge portion is lower than rigidity of the central portion.