You can freely build on How Piezoelectric Inkjet Printing Works

What this patent covers

This patent describes a drop-on-demand inkjet printing mechanism. Instead of spraying a continuous stream of ink, it ejects individual droplets only when needed. The system features a fluid chamber connected to a constant ink supply and a nozzle orifice. One wall of the chamber contains a piezoelectric actuator made of two plates bonded together. When an electrical pulse is applied, these plates expand in opposite directions, causing the actuator to bend inward. This sudden volume reduction squeezes exactly one droplet of ink out of the nozzle at a rate of 100 to 3,000 drops per second.

What is now free to use

All 1 claims of US 3946398 are in the public domain. Specifically:

• Claim 1: The method of projecting writing fluid droplets from an orifice — 1 specific element

The 0 dependent claims add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Does not cover continuous inkjet printing where a constant stream of droplets is electrostatically deflected.

• Does not cover thermal inkjet printing, which uses heat resistors to vaporize ink and create a bubble to eject drops.

• Does not cover printing rates outside the claimed range of 100 to 3,000 droplets per second.

• Does not cover single-layer piezoelectric actuators that do not use two transversely expanding plates secured together to bend.

Who is building on this today

Epson continues to dominate the consumer and industrial space with its proprietary Micro Piezo technology. Industrial printhead manufacturers like Fujifilm Dimatix and Xaar also build high-performance micro-electromechanical systems (MEMS) based on these early piezo deflection principles.

Products built on expired version of this technology

How to cite this patent in your documentation

SILONICS Inc. US Patent 3946398. Method and apparatus for recording with writing fluids and drop projection means therefor. Granted 1976, expired 1993. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.