LIQUID LEVEL SENSOR WITH LEVEL ALARM

• US 20080271527A1
• Filed: 06/20/2008
• Published: 11/06/2008
• Est. Priority Date: 05/01/2007
• Status: Active Grant

• Current Assignee: John T. Hewitt
• Original Assignee: John T. Hewitt
• Inventors: Hewitt, John T.
• Granted Patent: US 7,658,104 B2
• Time in Patent Office: Days
• US Class Current: 73/299
• CPC Class Codes: G01F 23/164 using a diaphragm, bellow as transmitting element
• CPC Class Codes: G01F 23/18 Indicating, recording or alarm devices actuated electrically
• CPC Class Codes: G01F 25/20 of apparatus for measuring liquid level
• CPC Class Codes: G01L 7/063 with mechanical transmitting or indicating means

Abstract

A liquid level sensor system actuated by a column pressure includes a hollow member having a distal open end adapted to be positioned into a liquid reservoir to a depth below a liquid surface level, and a sensor head unit. The sensor head unit is responsive to the column pressure to provide an indication of a liquid level in the reservoir. A low liquid level alarm circuit is responsive to the bellows member to generate a signal indicative of a low liquid level state.

Claims

1. A liquid level sensor, comprising:

a hollow member having a distal open end adapted to be positioned into a liquid reservoir to a depth below a liquid surface level;

a sensor head unit;

a connection tubing system adapted to provide a closed connection between the hollow member and the sensor head unit, such that a column pressure in said hollow member is transmitted to the sensor head unit;

said sensor head unit comprising;

a bellows member having an input stem portion adapted for connection to the connection tubing system, an expandable body portion and a distal bellows face surface, the bellows body adapted for expansion and contraction in response to differential column pressure changes so that said bellows face surface translates along a range of movement;

a non-electrically-powered mechanism responsive to movement of said bellows face surface to provide an indication of said liquid surface level at each liquid level within a range of liquid levels from a full or high liquid level and a lower liquid level; and

a low liquid level alarm circuit responsive to the bellows member to generate a signal indicative of a low liquid level state.

2. The sensor of claim 1, wherein the low liquid level alarm circuit is responsive to the distal bellows face surface withdrawing below a threshold position to generate said signal.

3. The sensor of claim 1, wherein the low liquid level alarm circuit includes a contact arm supported at a location within said range of movement corresponding to threshold position.

4. The sensor of claim 3, wherein said bellows member is fabricated of an electrically conductive material, and said low level alarm circuit is configured to sense the presence or absence of electrical continuity between said contact arm and said bellows member.

5. The sensor of claim 3, wherein said sensor head unit comprises:

a housing structure, the bellow member supported within the housing unit;

a adjustment mechanism for adjusting the position of the bellow member relative to said non-electrically-powered mechanism, wherein a position of the bellows face surface may be adjusted by said adjustment mechanism; and

wherein the low liquid level alarm circuit includes a support structure for said contact arm and an adjusting mechanism for adjusting the position of said contact arm within said range of movement to adjust said threshold position.

6. The sensor of claim 5, wherein said support structure includes a dielectric riser structure attached to the contact arm and configured for sliding movement in said housing structure, and a movable member arranged to contact the riser structure to set a position of the contact arm within the range of movement.

7. The sensor of claim 6, wherein the adjusting mechanism further includes a bias member for exerting a bias force on the riser structure in opposition to a force exerted by the movable member.

8. The sensor of claim 4, wherein the alarm circuit includes a contact boss member for making electrical contact with the bellows member to provide a circuit contact such that said electrical continuity is through said contact boss, said bellows member and said contact arm.

9. The sensor of claim 8, wherein said contact boss is mounted for movement along an axis, and is urged into physical contact with the bellows by a bias support structure.

10. The sensor of claim 1, wherein said hollow member is a rigid tube, and said distal end is adapted to be positioned at a depth in the reservoir below a low or empty liquid level.

11. The sensor of claim 1, further including a warning light, said signal activating the warning light to provide an indication of a low liquid level condition.

12. A liquid level sensor, comprising:

a hollow member having a distal open end adapted to be positioned into a liquid reservoir to a depth below a liquid surface level;

a sensor head unit;

a connection tubing system adapted to provide a closed connection between the hollow member and the sensor head unit, such that a column pressure in said hollow member is transmitted to the sensor head unit;

said sensor head unit comprising;

a bellows member having an input stem portion adapted for connection to the connection tubing system, an expandable body portion and a distal bellows face surface, the bellows body adapted for expansion and contraction in response to differential column pressure changes so that said bellows face surface translates along a range of movement, the bellows member fabricated of an electrically conductive material;

a non-electrically-powered mechanism responsive to movement of said bellows face surface to provide an indication of said liquid surface level at each liquid level within a range of liquid levels from a full or high liquid level and a lower liquid level; and

a low liquid level alarm circuit responsive to travel of the bellows face surface along the range of movement to activate a low liquid level state alarm signal.

13. The sensor of claim 12, wherein the low liquid level alarm circuit is responsive to the distal bellows face surface withdrawing below a threshold position to generate said signal.

14. The sensor of claim 13, wherein the low liquid level alarm circuit includes an electrically conductive contact arm supported at a location within said range of movement corresponding to said threshold position.

15. The sensor of claim 14, wherein said low level alarm circuit is configured to sense the presence or absence of electrical continuity between said contact arm and said bellows member.

16. The sensor of claim 14, wherein said sensor head unit comprises:

a housing structure, the bellow member supported within the housing unit;

a adjustment mechanism for adjusting the position of the bellow member relative to said non-electrically-powered mechanism, wherein a position of the bellows face surface may be adjusted by said adjustment mechanism; and

wherein the low liquid level alarm circuit includes a support structure for said contact arm and an adjusting mechanism for adjusting the position of said contact arm within said range of movement to adjust said threshold position.

17. The sensor of claim 15, wherein the alarm circuit includes a contact boss member for making electrical contact with the bellows member to provide a circuit contact such that said electrical continuity is through said contact boss, said bellows member and said contact arm.

18. The sensor of claim 12, further including a warning light, said alarm signal activating the warning light to provide an indication of a low liquid level condition.

19. The sensor of claim 12, further comprising a relay activated by said alarm circuit to disable operation of a machine using the liquid in the reservoir.