Liquid level sensing system
First Claim
1. A liquid level sensing system for sensing a liquid level in a container, comprising:
- a probe at least partially receivable in the container, said probe being adapted to have a compressible fluid therein with the pressure of the fluid being related to the level of the liquid in the container;
means responsive to the pressure in the probe dropping below a predetermined level for supplying fluid under pressure to the probe; and
means responsive to the pressure in the probe remaining below said predetermined level for a predetermined time to provide an indication of low liquid level in the container.
2 Assignments
0 Petitions
Accused Products
Abstract
A sensing system for detecting a low level of liquid in a container employs an open-ended probe which is partially submerged in the liquid. The probe contains a pressurized compressible fluid, typically air, the pressure of which is related to the level of the liquid in the container, being a function of the static head of the liquid. A pressure switch fluidly connected to the probe is actuated when the pressure in the probe falls below a predetermined level. The pressure switch activates an air pump, which pumps compressed air into the probe to try and restore the predetermined pressure level, and the switch simultaneously actuates a time delay unit, which in turn initiates a time delay period. If pressure in the probe is restored to the predetermined level prior to the expiration of the time delay period, the time delay unit is reset and the air pump is shut off, since restoration of the pressure indicates that the liquid level is not really low, the low pressure condition is caused by a leak or absorption. However, if the pressure in the probe is not restored to the predetermined level when the time delay period expires, an alarm indicating low liquid level in the container is actuated, so that the level may be replenished.
53 Citations
9 Claims
-
1. A liquid level sensing system for sensing a liquid level in a container, comprising:
-
a probe at least partially receivable in the container, said probe being adapted to have a compressible fluid therein with the pressure of the fluid being related to the level of the liquid in the container; means responsive to the pressure in the probe dropping below a predetermined level for supplying fluid under pressure to the probe; and means responsive to the pressure in the probe remaining below said predetermined level for a predetermined time to provide an indication of low liquid level in the container. - View Dependent Claims (2, 3, 4)
-
-
5. A liquid level sensing system for sensing a liquid level in a container comprising:
-
a probe at least partially receivable in the container, said probe having an open lower end and having a compressible gas therein, with the pressure of the gas being related to the level of the liquid in the container; a pressure switch in fluid communication with said probe, said pressure switch being actuated when the pressure in the probe drops below a predetermined level; and a pressurized fluid supply means, responsive to the actuation of said pressure switch, for supplying pressurized fluid to said probe, said pressurized fluid supply means ceasing supply of pressurized fluid to the probe when the fluid pressure in said probe again exceeds the predetermined level. - View Dependent Claims (6, 7)
-
-
8. A method for sensing liquid level in a container comprising the steps of:
-
inserting a probe having a compressible fluid therein into the liquid in said container, the pressure of the compressible fluid being related to the level of the liquid in the container; sensing the fluid pressure in said probe; supplying pressurized fluid to said probe when the fluid pressure therein falls below a predetermined level; and indicating a low liquid level in the container if the fluid pressure in said probe remains below a predetermined level for a predetermined period of time. - View Dependent Claims (9)
-
Specification