Liquid flow control

• US 4,257,437 A
• Filed: 01/19/1979
• Issued: 03/24/1981
• Est. Priority Date: 02/08/1978
• Status: Expired due to Term

• Current Assignee: Imperial Chemical Industries Limited (Nouryon BV)
• Original Assignee: Imperial Chemical Industries Limited (Nouryon BV)
• Inventors: Pearson, William B.
• Primary Examiner(s): Cohan, Alan
• Application Number:
  US06/004,922
• Time in Patent Office: 795 Days
• Field of Search: 137/395, 137/396, 137/8, 137/624.13, 137/624.15, 222/64
• US Class Current: 137/8
• CPC Class Codes: G05D 7/0635 by action on throttling means G05D7/0688, G05D7/0694 take precedence
• CPC Class Codes: Y10T 137/0357 For producing uniform flow
• CPC Class Codes: Y10T 137/7316 Self-emptying tanks

Abstract

A method and apparatus to control the flow of liquid through a valve, especially at very low levels down to about 0.5 ml/hour, by monitoring the liquid level in a column of liquid using a sensor, for example a photo-electric cell, which is moved along the column at a predetermined rate corresponding to the liquid flow rate desired, generating a signal from the sensor which is representative of the liquid level, and using the signal to control the opening and closing of the valve to maintain the liquid flow at the desired rate.

Claims

1. A method of controlling the rate of flow of liquid from a column through a valve which comprises moving a sensor for the level of liquid in the column along the column at a pre-determined rate corresponding to the desired rate of flow of liquid through the valve, generating a signal from the sensor which represents the liquid level in the column relative to the sensor, and controlling the opening and closing of the valve in response to the signal generated by the sensor whereby liquid flows through the valve at the desired rate.

2. A method as claimed in claim 1 in which the sensor used is a light-sensitive sensor.

3. A method as claimed in claim 1 in which the column is used in a vertical or near vertical position.

4. A method as claimed in claim 1 in which the rate of liquid flow is monitored by at least one sensor which is used in a co-operative relationship with the sensor for the liquid level to generate a signal if the rate of liquid flow is outside pre-determined higher or lower limits.

5. A method as claimed in claim 1 in which the flow of liquid to the valve is supplied from one or other of at least two columns, each of which is provided with its own liquid level sensor, the columns being interconnected by a switching arrangement whereby liquid is supplied from each column in turn to provide a continuous flow to the valve.

6. Apparatus for controlling the rate of flow of liquid through a valve which comprises a column for holding the liquid, sensing means for the level of liquid in the column and movable along the column at a pre-determined rate, the sensing means including means for generating a signal representative of the level of liquid in the column relative to the sensor, and means to convey said signal to control means controlling the opening and closing of the valve.

7. Apparatus as claimed in claim 6 in which the sensing means is a light-sensitive sensor.

8. Apparatus as claimed in claim 6 and including sensing means to work in co-operative relationship with the liquid level sensing means to monitor the rate of liquid flow and generate a signal if the rate of liquid flow is outside pre-determined higher or lower limits.

9. Apparatus as claimed in claim 6 comprising at least two columns for holding the liquid, each column having sensing means for the level of liquid in that column, and switching means to allow the flow of liquid from one column to be terminated and to be immediately replaced by flow of liquid from another column without interruption to the flow of liquid through the valve.