You can freely build on How Dr. Forrest Bird's Mechanical Respirator Controls Patient Breathing

What this patent covers

The device acts as an automated breathing controller that connects a pressurized gas source to a patient's airway. It uses a main valve to toggle between inhalation and exhalation phases. The system monitors the air pressure at the patient's airway; when the pressure hits a specific threshold, the controller automatically closes the valve to end inhalation. If the pressure fails to reach that threshold within a set time, a secondary valve system triggers an additional flow of gas to ensure the patient receives the required volume of air.

What is now free to use

All 1 claims of US 3191596 are in the public domain. Specifically:

• Claim 1: IN A RESPIRATORY APPARATUS HAVING AN INHALATION PHASE AND AN EXHALATION PHASE IN ITS OPERATIVE CYCLE, A CONTROLLER HAVING AN INLET ADAPTED TO BE CONNECTED TO A SOURCE OF GAS UNDER PRESSURE, SAID CONTROLLER HAVING AN OUTLET ADAPTED TO BE CONNECTED TO THE AIRWAY OF THE PATIENT, A MAIN CONTROL VALVE IN THE CONTROLLER MOVABLE BETWEEN OPEN AND CLOSED POSITIONS TO CONTROL THE FLOW OF GAS FROM THE INLET TO THE OUTLET, MEANS FOR OPERATING SAID MAIN CONTROL VALVE SO THAT THE MAIN CONTROL VALVE IS IN AN OPEN POSITION DURING THE INHALATION PHASE AND IN A CLOSED POSITION DURING THE EXHALATION PHASE OF THE RESPIRATORY APPARATUS, SAID MEANS — 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 electronic or microprocessor-based control systems.

• Does not cover non-pressure-sensitive ventilation methods.

• Does not cover portable manual resuscitation bags (Ambu bags).

Who is building on this today

Companies like Hamilton Medical, Dräger, and GE Healthcare continue to build on the principles of pressure-cycled ventilation established by Bird. These manufacturers have evolved the pneumatic logic into sophisticated digital systems that monitor patient lung compliance in real-time.

Products built on expired version of this technology

How to cite this patent in your documentation

Individual. US Patent 3191596. Respirator. Granted 1965, expired 1982. 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.