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1. (WO1991006336) PRESSURE SENSOR CONTROL DEVICE FOR SUPPLYING OXYGEN
Nota: O texto foi obtido por processos automáticos de reconhecimento ótico de caracteres.
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We claim:
1. A flow control device for controlling the flow of oxygen to a patient, said device comprising:
(a) flow valve means for controlling the amount of oxygen flowing from an oxygen supply to a patient; and
(b) electronic control means comprising (i) pressure sensor means for sensing pressure changes in the breathing of the patient and for producing sensor output signals in accordance therewith, (ii) feedback means for feeding back said sensor output signals to the pressure sensor means to provide automatic correction of said sensor output signals, the feedback means comprising switch means for automatically disconnecting said feedback means as a function of the sensor output signals, and (iii) control signal generation means connected to said pressure sensor means for producing control signals based on said sensor output signals and for applying said control signals to said flow valve means to control the flow of oxygen to the patient.

2. A flow control device according to claim

1, wherein said pressure sensor means comprises amplifier means connected to a sensor output for producing an amplified output signal.
3. A flow control device according to claim

2, wherein the control signal generation means comprises comparing means for receiving the amplified output signal and comparing said output signal with a variable threshold level to selectively output a comparator trigger signal for generating said control signals.

4. A flow control device according to claim

3, wherein said feedback means comprises integrator means having a time constant of at least 5 seconds duration and means for feedback signal inversion, connected in series with the switch means, for providing a negative integral feedback signal to the amplifier means.
5. A flow control device according to claim

4, wherein said switch means comprises a first switch position and a second switch position for disconnecting the feedback means from the pressure sensor means at predetermined times.
6. A flow control device according to claim

5, wherein said switch means disconnects the feed- . back means from the pressure sensor means when oxygen flows through the flow valve means, and connects the feedback means to the pressure sensor means at least a part of the time when oxygen does not flow through the flow valve means.
7. A flow control device according to claim

6, wherein said switch means disconnects the feedback means from the pressure sensor means when oxygen flows through the flow valve means and for approximately 0.5 seconds thereafter, and connects the feedback means to the pressure sensor means at all other times.
8. A flow control device according to claim 5, wherein said feedback means comprises a first correction circuit means for counterbalancing the effect of the integrator means not being connected when said feedback means is disconnected, said first correction circuit means providing a first voltage drop within said feedback means when said feedback means is disconnected so to increase the average value of said amplified output signal.
9. A flow control device according to claim

8, wherein said first correction circuit means comprises a series connection of a first resistor for receiving the amplified output signal, a first diode, and a second resistor, with said first voltage drop occurring at a junction of said first resistor and said first diode.
10. A flow control device according to claim

9, wherein said feedback means comprises a second correction circuit means for increasing the rate at which said amplified output signal shifts back above said threshold level, said second correction circuit being activated to provide a second voltage drop within said feedback means only when the amplified output signal is less than said threshold level for a predetermined time period after oxygen has ceased to be delivered through said flow valve means.
11. A flow control device according to claim

10, wherein said second correction circuit means comprises components that include a capacitor for setting said predetermined time period, a third resistor, a transistor and second and third diodes, whereby all of said components have a common point of connection, said third resistor and said second diode are connected in parallel, and said second voltage drop is produced at said junction of the first resistor and the first diode.
12. A flow control device according to claim 9, wherein said control signal generation means comprises hold-off timer means for receiving said comparator trigger signal and outputting a hold-off pulse of predetermined width, valve-on timer means for receiving the hold-off pulse and for generating a valve-on signal in response thereto for producing said control signals.
13. A flow control device according to claim

12, wherein said electronic control means comprises a delay time indicator connected to receive the hold-off pulse for measuring time between patient inhalations, and for generating an alarm signal when a predetermined time passes without detection of patient inhalation.
14. A flow control device according to claim

13, wherein said alarm signal is inputted to said flow valve means to actuate a flow of oxygen to the patient.
15. A flow control device according to claim 13, wherein said delay time indicator comprises an adjustable timer and indicator means for alerting an operator when said alarm signal is generated.
16. A flow control device according to claim 13 , wherein said detection of patient inhalation is determined by receipt of pulses outputted from said hold-off timer means.
17. A flow control device according to claim 13, wherein said predetermined time is user adjustable from approximately 6 to 60 seconds by a time constant circuit comprising a variable resistor.
18. A flow control device according to claim 13, wherein the delay time indicator comprises a transistor switch for generating said alarm signal, and deactivation means for automatically terminating said alarm signal when inhalation is resumed.

19. A flow control device according to claim 12, wherein the valve-on timer means comprises transistor switch means having a transistor base limiting resistor connected to receive the valve-on signal, and a transistor collector as an output terminal for connection of said control signals to said flow valve means.
20. A flow control device according to claim 12, wherein said control signal generation means comprises power-up timer means for generating a reset pulse when power is activated to the flow control device, said reset pulse being inputted to said hold-off timer means, to said valve-on timer means and to said feedback means for resetting the hold-off and the valve-on timer means, and for establishing a fast zero in said integrator means.
21. A flow control device according to claim 20, wherein said integrator means comprises zeroing means for receiving said reset pulse and changing said integrator time constant to a value less than 0.5 seconds for quickly establishing a zero reference within said integrator means.
22. A flow control device according to claim 20, wherein the reset pulse has a pulse width determined by a capacitor-resistor circuit.
23. A flow control device according to claim 22, wherein a delay occurs before output of said reset pulse after said power is activated, the time of the delay being adjustably determined by a capacitor-resistor combination.
24. A flow control device according to claim 12, wherein the predetermined width of the hold-off pulse is determined by a resistor-capacitor circuit for blocking an output of other signals from said hold-off timer means while said hold-off pulse is being outputted.
25. A flow control device according to claim 24, wherein said hold-off pulse has a pulse width of approximately 1.5 seconds.
26. A flow control device according to claim 12, wherein the valve-on timer means is triggered by an inverted front edge of said hold-off pulse.
27. A flow control device according to claim 1, wherein said flow valve means comprises a solenoid valve having an input terminal for receiving said control signal for opening and closing said solenoid valve, a first valve port for receiving a regulated oxygen supply through an orifice, a second valve port for outputting oxygen to a patient, and transfer means for receiving pressure variations from the patient and delivering said pressure variations to said pressure sensor means.
28. A flow control device according to claim 27, wherein said transfer means is deactivated during the time that oxygen flows through the solenoid valve to the patient.
29. A flow control device according to claim 12, wherein the valve-on timer means comprises adjustable switch means for varying a pulse width of said control signals to select a time interval of oxygen flow.
30. A flow control device according to claim 29, wherein said adjustable switch means comprises a six position switch for varying the control signal pulse width to produce time intervals of oxygen flow from 100 ms to 500 ms in equal switch position increments
31. A flow control device according to claim 12, wherein said hold-off timer means comprises a hold-off first output for output of said hold-off pulse, and a hold-off second output for concurrent output of an inverted hold-off pulse, with said second output connected as input to said first correction circuit for activation of said first correction circuit during the input of the inverted hold-off pulse.