Can anyone suggest whether the assignee for US7530675 would be successful in a law suit asserting this patent given earlier examples of rectangular actuators with similar "underlap" ratios?
Here's why I ask.
Mechanical piezoelectric actuators for inkjets have been around for over 40 years. Every inkjet designer since has optimized the performance of the actuator by finding the best ratio of the width of the piezoceramic element to the chamber width. The answer usually falls between 60% and 100% for most device geometries. Nonetheless, patent applications are still filed with broad claims covering this ratio and being granted. One such is US7530675.
I poked around in older patents and found US4730197 which says in the description: "The neutral plane of the bender or driver formed by the transducer 114 and the diaphragm plate 110 should be near the bond plane between the two components. This requires that the plate stiffness of the diaphragm is about the same as for the transducer. These requirements determine the thickness of the transducer and the diaphragm, as a function of the compression chamber width and length. The width of the transducer is determined to optimize the voltage response of the ink jet. The preferred range is 80 to 100% of the width of the compression chamber. The length of the transducer is approximately equal to the length of the compression chamber.”
US7530675 claims a "....ratio of the first dimension to the second dimension ranging from about 0.70 to about 0.99." It seems to me US4730197 knocks a big hole in US7530675. At best US7530675 should have been allowed to protect this ratio for narrow ranges of variables (the variables being those found in US4730197 and perhaps others that should have been cited). The prior art citations in this patent listed for the applicant and the examiner are woeful. All but one are to IP from the applicant's company and the one other describes actuators close to square in shape.