Inkjet printhead having bicuspid valved ink ejection arrangement

1. An inkjet printhead comprising ink ejection arrangements of an ink chamber, a nozzle defined in a first wall of the ink chamber and an ink ejector positioned within an aperture defined in an opposite, second wall of the ink chamber, the ink chamber being arranged in fluid communication with an ink supply channel via the aperture so as to supply ink to the nozzle,

wherein the ink ejector incorporates a movable paddle which is operable to cause ejection of ink from the nozzle and resupply of ink to the ink chamber from the ink supply channel, and

the adjacent, peripheral regions of the second wall and the paddle are configured to define a bicuspid valve between the ink chamber and the ink supply channel,

wherein the paddle incorporates a depression and/or a groove projection in the paddle, the depression and/or groove projection being a truncated pyramid.

2. An inkjet printhead according to claim 1 , wherein the bicuspid valve is defined by the peripheral regions of the second wall and paddle which are upturned toward the nozzle relative to other regions of the paddle and the aperture.

3. An inkjet printhead according to claim 1 , wherein the paddle incorporates a ridge on the paddle.

4. An inkjet printhead according to claim 3 , wherein a plurality of grove projections and/or ridges are incorporated, with each groove projection and/or ridge being parallel, concentric or intersecting.

5. An inkjet printhead according to claim 1 , wherein the paddle and the aperture have concentric circular shapes, with the paddle being positioned radially inward of the aperture so as to define a substantially annular aperture therebetween.

6. An inkjet printhead according to claim 5 , wherein the ink ejector further incorporates a thermal actuator coupled to the paddle, the thermal actuator being operable to move the paddle from a rest position, which is co-planar with the aperture, to an ejection position, which is toward the nozzle with respect to the aperture, and back to the rest position so as to cause the ejection and resupply of ink.

7. An inkjet printhead according to claim 6 , wherein the thermal actuator is coupled to the paddle by first and second arms, the first arm being connected to an electrical current source so as to be heated upon application of an electrical current and cooled upon cessation of the electrical current, the heating of the first arm causing thermal expansion of the first arm relative to the second arm thereby causing movement of the paddle from the rest position to the ejection position and the cooling of the first arm causing thermal contraction of the first arm relative to the second arm thereby causing movement of the paddle from the ejection position to the rest position.