You can freely build on How a Single Coil Powers Multiple Motor Armatures Simultaneously
This patent expired in 1992. Every claim — 0 independent, 1 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
Individual
Patent granted
1973
Expired
1992
Forward citations
22
What this patent covers
This patent describes a motor assembly where multiple armatures are placed in a circular pattern between two disks. These disks have interlocking finger-like projections that act as magnetic poles. A single central electromagnetic coil sits between the disks, creating a magnetic field that flows through these fingers to drive all the armatures at once. Essentially, it allows one power source to run multiple rotating parts simultaneously within a compact, integrated housing.
What is now free to use
All 1 claims of US 3723796 are in the public domain. Specifically:
The 1 dependent claim 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 motors using permanent magnets instead of an electromagnetic coil.
Does not cover linear motors where the armatures move in a straight line.
Does not cover single-armature motors.
Does not cover motors where the armatures are not arranged in a circular, parallel array.
Who is building on this today
Modern manufacturers of multi-spindle heads and synchronized robotic end-effectors continue to explore shared-flux motor designs to reduce weight in collaborative robots.
Products built on expired version of this technology
Early multi-spindle industrial drills
Compact automated assembly line actuators
How to cite this patent in your documentation
Individual. US Patent 3723796. Multi-armature motor. Granted 1973, expired 1992. 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.