Continuous liquid level measurement system

• US 6,298,721 B1
• Filed: 09/03/1999
• Issued: 10/09/2001
• Est. Priority Date: 09/03/1999
• Status: Expired due to Fees

• Current Assignee: Cummins Incorporated
• Original Assignee: Cummins Incorporated
• Inventors: Dringenburg, Dean H., French, Mike, Schneider, Matthew L., Schuppe, Alfred, Weng, Weibo
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): LOO, DENNIS S
• Application Number:
  US09/390,615
• Time in Patent Office: 767 Days
• Field of Search: 732/99, 733/01, 733/00, 733/02, 732/90.B, 732/90.R, 367/149
• US Class Current: 73/299
• CPC Class Codes: G01F 23/04 by dip members, e.g. dip-sticks
• CPC Class Codes: G01F 23/164 using a diaphragm, bellow as transmitting element

Abstract

A continuous liquid level measurement system is disclosed which is based upon a differential pressure measurement. The pressure of the liquid level to be measured is calibrated with a second pressure measurement of the pressure above the liquid in order to get a more accurate pressure measurement which is related in a predetermined manner to the level of the liquid. For instances in which the liquid to be measured is in a harsh environment, the invention provides for a means for mounting the sensitive pressure measurement devices remotely from the liquid.

Claims

1. A continuous liquid level measurement system, comprising:

a shaft having a proximal end and a distal end;

a differential pressure transducer disposed at the proximal end and having a first pressure input and a second pressure input;

a flexible bladder disposed at the distal end;

a first pressure transmission tube disposed within the shaft and coupling the bladder to the first pressure input for substantial equalization of pressure therebetween;

a reference pressure port formed in the shaft proximal of the bladder; and

a second pressure transmission tube disposed within the shaft and coupling the reference pressure port to the second pressure input for substantial equalization of pressure therebetween;

wherein when the bladder is placed below the liquid level and the reference pressure port is placed above the liquid level, the differential pressure transducer will measure a pressure of the liquid on the bladder, and thus the liquid level.

2. The system of claim 1, wherein the shaft is flexible.

3. The system of claim 2, wherein the shaft comprises a spring.

4. The system of claim 1, further comprising:

a flexible diaphragm disposed between the first and second pressure inputs.

5. The system of claim 1, further comprising:

a threaded surface formed on the shaft distal of the differential pressure transducer.

6. The system of claim 5, further comprising:

a seal disposed between the threaded surface and the differential pressure transducer.

7. The system of claim 1, further comprising:

a substantially rigid shroud substantially covering the bladder, the shroud including at least one opening therein for pressure communication between the liquid and the bladder.

8. The system of claim 1, wherein the bladder is substantially inflexible in one direction.

9. The system of claim 1, further comprising:

an internal combustion engine including an engine block and an oil pan coupled thereto;

wherein the shaft extends through the engine block such that the proximal end is external to the engine block and the bladder extends to the oil pan.

11. The system of claim 1, wherein the signal processor comprises an electronic comparator.

12. The system of claim 1, wherein the shaft is flexible.

13. The system of claim 12, wherein the shaft comprises a spring.

10. A continuous liquid level measurement system, comprising:

a shaft having a proximal end and a distal end;

a first pressure transducer disposed at the proximal end and having a first pressure input and a first pressure output signal;

a second pressure transducer disposed at the proximal end and having a second pressure input and a second pressure output signal;

a signal processor coupled to the first and second pressure output signals and operative to produce a difference output signal substantially equal to a difference between the first and second pressure output signals;

a flexible bladder disposed at the distal end;

a first pressure transmission tube disposed within the shaft and coupling the bladder to the first pressure input for substantial equalization of pressure therebetween;

a reference pressure port formed in the shaft proximal of the bladder; and

a second pressure transmission tube disposed within the shaft and coupling the reference pressure port to the second pressure input for substantial equalization of pressure therebetween;

wherein when the bladder is placed below the liquid level and the reference pressure port is placed above the liquid level, the difference output signal will be proportional to a pressure of the liquid on the bladder, and thus the liquid level.

14. The system of claim 10, further comprising:

a threaded surface formed on the shaft distal of the first and second pressure transducers.

15. The system of claim 14, further comprising:

a seal disposed between the threaded surface and the first and second pressure transducers.

16. The system of claim 10, further comprising:

a substantially rigid shroud substantially covering the bladder, the shroud including at least one opening therein for pressure communication between the liquid and the bladder.

17. The system of claim 10, wherein the bladder is substantially inflexible in one direction.

18. The system of claim 10, further comprising:

an internal combustion engine including an engine block and an oil pan coupled thereto;

wherein the shaft extends through the engine block such that the proximal end is external to the engine block and the bladder extends to the oil pan.