| 摘要 |
<p>An oxygen concentrator is provided which has a first molecular sieve bed connected to a four-way valve (i.e., a cross-over valve) which either joins the sieve bed to a pressurized air source (compressed air) or alternatively vents it to atmosphere. A second molecular sieve bed is also joined to the four-way valve in a corresponding manner. One bed is joined to the compressed air to produce oxygen-enriched air while the other is vented to atmosphere to cause evacuation. The sieve beds are joined at the outlet end to a product reservoir. The oxygen-enriched product gas passes from the reservoir to the patient. The sieve beds are also in fluid communication at the outlet end by means of a pressure equalization flow path. A concentration equalization valve regulates the flow in the pressure equalization flow path. In order to purge the nitrogen from a used molecular sieve bed, a quantity of oxygen-enriched air is passed into the bed immediately before it is vented to atmosphere. In accordance with the present invention, the microprocessor uses a closed-loop feedback circuit to evaluate the amount of time that the output product gas is allowed to flow into the used sieve bed. Specifically, an incremental step advance is used assuming a peak value of the time of flow in one direction as compared to the time of flow in the second direction. In a second embodiment, control means is provided based on a variable residence time range and variable pressure set point.</p> |
