How Piezoelectric Inkjet Printing Works
A 1970 patent describing how to print images by using electrical pulses to bend a tiny crystal plate, squeezing individual ink drops out of a nozzle on demand.
Original patent title: “Method and apparatus for recording with writing fluids and drop projection means therefor”
A 1970 patent describing how to print images by using electrical pulses to bend a tiny crystal plate, squeezing individual ink drops out of a nozzle on demand. Granted to SILONICS Inc in 1976 with 6 claims and 448 forward citations, and it is now in the public domain.
Key facts
Coverage
What does this patent actually cover?
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.
The gap
What does this patent NOT cover?
- 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.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
Using a bimorph piezoelectric actuator—two plates that expand in opposite directions when electrified—to act as a tiny, solid-state pump. This bending motion creates a highly controllable, rapid physical displacement without moving parts like gears or pistons.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Epson Micro Piezo printheads
Brother desktop inkjet printers
Industrial wide-format UV flatbed printers
Piezoelectric 3D bioprinters
Why it matters
The bigger picture
This patent is a foundational document for drop-on-demand piezoelectric inkjet printing. This technology eventually enabled high-resolution color home printing, industrial textile printing, and modern 3D bioprinting. It avoided the messy ink-recirculation systems required by earlier continuous inkjet printers.
Filed
June 29, 1970
Granted
March 23, 1976
Market context
Who's building on this
Companies in this space
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.
Market impact
This technology shifted the inkjet market away from complex, high-maintenance continuous stream systems toward reliable, consumer-friendly desktop printers. It laid the technical foundation for modern high-resolution industrial printing on textiles, ceramics, and electronics.
Claim 1 — Plain English
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.
The clever bit
Using a bimorph piezoelectric actuator—two plates that expand in opposite directions when electrified—to act as a tiny, solid-state pump. This bending motion creates a highly controllable, rapid physical displacement without moving parts like gears or pistons.
What it does not cover
- 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.
Patent Journey
From filing to expiry
PatentBrief Score
Impact Score
Moderate
Citation count
40/40
Highly cited
Claim breadth
4/20
Moderate scope
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$41K – $130K
Midpoint $81K · expired or expiring · industry ×0.9
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
The original legal language
Original claims
6 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Sears, S. B., & Kyser, E. L. (1976). How Piezoelectric Inkjet Printing Works (U.S. Patent No. 3,946,398). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/3946398/drop-on-demand-inkjet
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Piezoelectric Inkjet Printing Works cover?
A 1970 patent describing how to print images by using electrical pulses to bend a tiny crystal plate, squeezing individual ink drops out of a nozzle on demand.
Who owns patent US 3946398?
SILONICS Inc owns this patent, granted in 1976.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 3946398 cited by?
This patent has been cited by 448 later patents that build on its ideas.
What problem does this patent solve?
This patent is a foundational document for drop-on-demand piezoelectric inkjet printing. This technology eventually enabled high-resolution color home printing, industrial textile printing, and modern 3D bioprinting. It avoided the messy ink-recirculation systems required by earlier continuous inkjet printers.
What does this patent NOT cover?
Does not cover continuous inkjet printing where a constant stream of droplets is electrostatically deflected.
Patent monitoring