You can freely build on How Gideon Sundback Invented the Modern Zipper
This patent expired in 1934. Every claim — 0 independent, 0 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
Hookless Fastener Co
Patent granted
1917
Expired
1934
Forward citations
14
What this patent covers
This patent describes a mechanism for joining two edges of fabric using a series of interlocking teeth mounted on flexible tapes. The device uses a sliding cam, or slider, to force the teeth together when moving in one direction and to pry them apart when moving in the other. By alternating the position of the teeth and using a specific spring-loaded locking mechanism, the fastener ensures that the teeth remain securely engaged even when under tension.
What is now free to use
All 0 claims of US 1219881 are in the public domain. Specifically:
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 non-interlocking fasteners like buttons, hooks, or snaps.
Does not cover magnetic or adhesive-based fastening systems.
Does not cover zippers that use continuous coils instead of individual metal teeth.
Who is building on this today
The Hookless Fastener Company eventually became YKK, which remains the dominant global manufacturer of fastening systems today. Many modern textile manufacturers continue to utilize the fundamental mechanical principles established in this 1917 patent.
Products built on expired version of this technology
Standard metal zippers on denim jeans
Fasteners on heavy-duty canvas bags
Military-grade gear and field equipment
How to cite this patent in your documentation
Hookless Fastener Co. US Patent 1219881. Separable fastener.. Granted 1917, expired 1934. 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.