System and method for operating a respirator compressor system under low voltage conditions

• US 5,368,019 A
• Filed: 12/16/1992
• Issued: 11/29/1994
• Est. Priority Date: 12/16/1992
• Status: Expired due to Term

• Current Assignee: Puritan Bennett Corp. (Medtronic Plc)
• Original Assignee: Puritan Bennett Corp. (Medtronic Plc)
• Inventors: Latorraca, Gary
• Primary Examiner(s): Burr, Edgar S.
• Assistant Examiner(s): Lewis, Aaron J.
• Application Number:
  US07/991,442
• Time in Patent Office: 713 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.23, 417/28, 417/29, 417/282, 417/44 A
• US Class Current: 128/204.18
• CPC Class Codes: A61M 16/0057 Pumps therefor
• CPC Class Codes: A61M 16/0063 Compressors
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: F04B 2203/0202 Voltage
• CPC Class Codes: F04B 2205/063 in a reservoir linked to the pump outlet
• CPC Class Codes: F04B 49/065 and making use of computers

Abstract

The system and method for operating an AC respirator compressor system at substantially subnormal line voltages includes a compressor, an accumulator, a solenoid unload or dump valve used to reduce the pressure at the outlet of the compressor, a check valve located downstream from the solenoid, a relief valve, a pressure sensor, and an AC voltage sensor. In a preferred embodiment, the compressor constantly supplies compressed air to the ventilator system, monitoring the accumulator pressure and activating the solenoid unload valve as required to maintain an acceptable range of pressure in the accumulator. In another preferred embodiment the compressor system can also be operated in an intermittent, or standby mode, to supply compressed air as needed. The respirator compressor system can maintain an acceptable range of pressure in the accumulator even during periods of low AC line voltage by monitoring both the accumulator pressure and the AC line supplying voltage to the respirator compressor system, and modulating the action of the solenoid unload valve to achieve low AC voltage operation.

Claims

1. A method for operating a respirator compressor system at low voltage, said respirator compressor system including a rigid accumulator for temporarily storing gas within a desired pressure range for supplying the gas to a ventilator system, a gas compressor driven by an electric motor, said gas compressor having an inlet for gas to be compressed and an outlet for compressed gas in fluid communication with said accumulator, a solenoid unload valve connected in fluid communication with said outlet of said gas compressor for reducing the pressure at the outlet of the compressor, a pressure sensor for measuring gas pressure within said accumulator operative to generate an electrical signal indicating accumulator pressure, an AC voltage sensor for measuring voltage supplied to said electric drive motor of said gas compressor, and control logic means for controlling operation of said solenoid unload valve, comprising the steps of:

operating said gas compressor to charge said accumulator with pressurized gas;

measuring the gas pressure in the accumulator and generating an electrical gas pressure signal representing accumulator gas pressure;

measuring line voltage to the drive motor of the gas compressor, and generating an electrical line voltage signal representing said voltage;

providing a command signal to modulate the operation of the solenoid unload valve to lower the output pressure of the compressor responsive to said gas pressure signal and said line voltage signal, thus preventing compressor stall over a broader input voltage range than would otherwise be possible.

2. The method of claim 1, wherein the electrical respirator compressor system is operated at a reduced voltage as low as 65% of normal line voltage.

3. The method of claim 1, wherein the respirator compressor constantly supplies compressed air to the accumulator, and the electrical respirator compressor system maintains an acceptable pressure minimum in the accumulator even during periods of low voltage.

4. The method of claim 1, wherein the respirator compressor supplies compressed air to the respirator system in an intermittent or standby mode, and activates the compressor and activates the solenoid unload valve as required to maintain an acceptable minimum pressure in the accumulator during periods of low voltage.

5. A system for operating an electrical respirator compressor system at low voltage, comprising:

a rigid walled accumulator for temporarily storing gas within a desired pressure range for supplying the gas to a ventilator system;

a gas compressor having an electrical drive motor, and having an inlet for gas to be compressed and an outlet in fluid communication with said accumulator for supplying compressed gas at an output pressure to said accumulator;

a solenoid unload valve connected in fluid communication with said outlet of said gas compressor for reducing the pressure at the outlet of the compressor;

a relief valve for venting excess pressure from the accumulator;

a pressure sensor for measuring pressure within said accumulator operative to generate a signal indicating accumulator pressure;

a voltage sensor for measuring voltage supplied to said electrical drive motor of said gas compressor operative to generate a signal indicating the voltage supplied to said electrical drive motor; and

control logic means connected to said pressure sensor and said voltage sensor for receiving said line voltage signal and said signal indicating accumulator pressure, said control logic means operative to generate a signal for control of the solenoid unload valve to lower the output pressure of the compressor responsive to said gas pressure signal and said line voltage signal, thus decreasing the voltage at which compressor stall will occur.

6. The system of claim 5, wherein a check valve is located in fluid communication with said solenoid unload valve and downstream from the solenoid unload valve to prevent high pressure air contained in the accumulator from providing back pressure to the gas compressor.