Condition responsive apparatus

• US 4,599,902 A
• Filed: 10/01/1984
• Issued: 07/15/1986
• Est. Priority Date: 10/01/1984
• Status: Expired due to Fees

• Current Assignee: Mykrolis Corporation (Entegris Incorporated)
• Original Assignee: SPAN Instruments, Inc.
• Inventors: Gray, Tommy L.
• Primary Examiner(s): WOODIEL, DONALD
• Application Number:
  US06/656,490
• Time in Patent Office: 652 Days
• Field of Search: 73/705, 73/293, 73/733, 250/231 P, 250/231 SE, 377/53, 307/117, 33/DIG. 3
• US Class Current: 73/705
• CPC Class Codes: G01L 9/0032 using photoelectric means

Abstract

A condition responsive apparatus is provided including a pressure gauge having a Bourdon tube expandable in response to an external pressure. In the preferred embodiment, an optical coupler, including a solid state light source and a detector, is mounted in proximity to a vane attached to the Bourdon tube. As the Bourdon tube flexes with increased pressure, the vane passes between the light source and the detector, thus blocking the radiation from the light source. The detector includes a Darlington amplifier which forms part of a voltage divider network for connecting an output signal from the Darlington amplifier to a pulse generating circuit. In operation, when the vane connected to the Bourdon tube passes between the light source and the detector, the pulse generating circuit responds to an increased voltage across the output of the voltage divider and is thus triggered to turn on a control transistor. The control transistor serves to turn on a power transistor for controlling an alarm or other control element.

Claims

1. A condition responsive apparatus having a control member movable in response to a pre-determined physical condition, comprising:

an optical coupler including a solid state light source and a detector comprising an input photo transistor and an output driver transistor for producing an output signal;

a vane attached to the control member for movement therewith between the light source and the input photo transistor from a first position to a second position in response to a change in the physical condition;

a pulse generating circuit having an input for receiving a drive voltage and generating a control signal in response thereto;

a coupling circuit connected to the output driver transistor and in response to movement of the vane from the first position to the second position generating the drive voltage above a threshold level to said pulse generating circuit, said pulse generating circuit producing the control signal in response to the drive voltage above the threshold level; and

control means connected to said pulse generating circuit for receiving the control signal and in response thereto generating an output signal indicating movement of the control member in response to the change in physical condition.

2. The condition responsive apparatus as described in claim 1 wherein said coupling circuit includes a voltage divider circuit having a first arm comprising a first resistor and said Darlington amplifier, and a second arm comprising a second resistor.

3. The condition responsive apparatus as described in claim 2 wherein said first resistor is connected between a power supply and a collector terminal of said output driver transistor.

4. The condition responsive apparatus as described in claim 2 wherein said second resistor is connected between a voltage node at an output of the voltage divider, and ground, said voltage node being further connected to an emitter terminal of said output driver transistor.

5. A condition responsive apparatus having a control member movable in response to a pre-determined physical condition, comprising:

an optical coupler including a solid state light source and a detector;

a vane attached to said control member for movement therewith between said light source and said detector from a first position to a second position in response to a change in the physical condition;

a trigger circuit having an input for receiving a drive voltage and in response thereto generating a control signal;

a coupling circuit connected to said detector and in response to movement of said vane from the first position to the second position generating the drive voltage above a threshold level to the input of the trigger circuit, said trigger circuit generating the control signal in response to the drive voltage above the threshold level; and

control means including a control transistor having an input electrode connected to said trigger circuit and in response to the control signal generating an output signal indicating movement of the control member in response to a change in physical condition.

6. The condition responsive apparatus as described in claim 5 wherein said control means further includes a power transistor having a base, emitter and collector, said collector of said control transistor connected to said base of said power transistor.

7. A condition responsive apparatus, comprising:

a pressure gauge having a Bourdon tube expandable in response to an external pressure;

an optical coupler including a solid state light source and detector;

a vane attached to said Bourdon tube for movement between said light source and said detector from a first position to a second position in response to said external pressure;

a pulse generating circuit;

a voltage divider responsive to movement of said vane from said first position to said second position for connecting an output signal from said detector to said pulse generating circuit, said pulse generating circuit generating a control signal in response thereto;

control means connected to said pulse generating circuit for receiving said control signal and in response thereto generating an output signal; and

power means connected to said control means for applying said output signal to a load.

8. The condition responsive apparatus as described in claim 7 wherein said voltage divider includes first and second arms, said first arm including said detector and a first resistor, said second arm including a second resistor.

9. The condition responsive apparatus as described in claim 8 wherein said detector comprises a Darlington amplifier having an input photo-transistor, and an output driver transistor for producing said output signal.

10. The condition responsive apparatus as described in claim 8 wherein said second resistor is connected between a voltage node at an output of said voltage divider, and ground, said voltage node being further connected to an emitter terminal of said output driver transistor.

11. The condition responsive apparatus as described in claim 10 wherein said pulse generating circuit is a Schmitt trigger circuit having an input, said voltage node being connected to said input.

12. The condition responsive apparatus as described in claim 11 wherein said control means includes a control transistor having a base, emitter and collector, said base connected to an output of said Schmitt trigger circuit.

13. The condition responsive apparatus as described in claim 17 wherein said power means includes a power transistor having a base, emitter and collector, said collector of said control transistor being connected to said base of said power transistor.

14. A condition responsive apparatus, comprising:

a pressure gauge having a Bourdon tube expandable in response to an external pressure;

an optical coupler including a light-emitting diode and a Darlington amplifier detector, said Darlington amplifier detector including an input photo-transistor and an output driver transistor;

a vane attached to said Bourdon tube for movement therewith between said light-emitting diode and said photo-transistor from a first position to a second position in response to said external pressure;

a pulse generating circuit having an input connected to a voltage node, said voltage node being further connected to an emitter terminal of said output driver transistor;

a voltage divider having first and second arms, said first arm including a first resistor and said Darlington amplifier, said second arm having a second resistor, said first and second arms connected at said voltage node and serving to connect said output driver transistor to said pulse generating circuit, said pulse generating circuit generating a control signal in response to movement of said vane from said first position to said second position;

a control transistor connected to said pulse generating circuit for receiving said control signal and in response thereto generating an output signal indicating movement of said vane in response to said external pressure; and

a power transistor connected to said control transistor for applying said output signal to a load.

15. A condition responsive apparatus, comprising:

a pressure gauge having a Bourdon tube expandable in response to an external pressure;

an optical coupler including a solid state light source and a detector;

a vane attached to said Bourdon tube for movement between said light source and said detector from a first position to a second position in response to the external pressure;

a Schmitt trigger circuit having an input for receiving a drive voltage and in response thereto generating a control signal;

a coupling circuit connected to said detector and in response to movement of said vane from the first position to the second position generating the drive voltage above a threshold level to said Schmitt trigger circuit, said Schmitt trigger circuit generating a control signal in response to the drive voltage above the threshold level; and

control means connected to said Schmitt trigger circuit and in response to the output control signal therefrom generating an output signal to a load.

16. A condition responsive apparatus, comprising:

a pressure gauge having a Bourdon tube expandable in response to an external pressure and including an indicator responsive to the expansion of the Bourdon tube;

an optical coupler including a light emitting diode and a Darlington amplifier detector, said Darlington amplifier detector including an input photo transistor and an output driver transistor;

a vane attached to said Bourdon tube for movement therewith between said light emitting diode and said photo transistor from a first position to a second position in response to a change in external pressure;

a Schmitt trigger circuit having an input connected to a voltage node for receiving a drive voltage and in response thereto generating a control signal, said voltage node being further connected to the output driver transistor;

a coupling circuit connected to the output driver transistor of said Darlington amplifier detector and in response to movement of said vane from the first position to the second position generating the drive voltage above a threshold level to said Schmitt trigger circuit, said Schmitt trigger circuit generating the control signal in response to the drive voltage above the threshold level;

control means connected to said Schmitt trigger circuit and in response to the control signal generating an output signal; and

power means connected to said control means for applying the output signal to a load.