You can freely build on How Auto-Injectors Adjust Their Dose Using a Simple Spacer

What this patent covers

This patent describes an auto-injector mechanism that allows the same device to hold different amounts of liquid medication. It achieves this by placing a spacer between the spring-loaded plunger and the piston inside the medicine cartridge. By changing the thickness or presence of this spacer, the piston is pushed further into the cartridge, effectively shrinking the volume of the medicament chamber. This ensures that the device can be calibrated for specific doses without needing to redesign the entire spring-power assembly.

What is now free to use

All 0 claims of US 4031893 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 electronic or digital dose-setting mechanisms

• Does not cover devices that use multiple chambers to mix medications

• Does not cover needle-free jet injection systems

• Does not cover the internal spring-power release mechanism itself

Who is building on this today

Survival Technology Inc. was a pioneer in this space, and their work laid the foundation for modern auto-injector platforms. Today, major pharmaceutical and medical device companies like Pfizer, Mylan, and Becton Dickinson continue to refine these mechanical delivery systems for self-administration.

Products built on expired version of this technology

How to cite this patent in your documentation

Survival Technology Inc. US Patent 4031893. Hypodermic injection device having means for varying the medicament capacity thereof. Granted 1977, expired 1996. 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.