Claims
- 1. A proportional flow control valve for controlling the flow of a fluid through a flexible tube, comprising in combination:
a. first and second jaws for engaging opposing sides of the flexible tube; b. an actuator coupled to at least one of said first and second jaws for varying a separation distance between said first and second jaws, said actuator being adapted to vary said separation distance between an initial separation distance and a shut-off separation distance, the initial separation distance being small enough to at least partially deform the flexible tube while being large enough to avoid significant restriction of the flow of fluid therethrough, the shut-off separation distance being just small enough to essentially block the flow of fluid therethrough; and c. a control system for controlling said actuator to select the separation distance between said first and second jaws.
- 2. The proportional flow control valve recited by claim 1 further including a manual adjustment coupled to at least one of said first and second jaws for adjusting the initial separation distance between the first and second jaws, and hence, adjusting the amount by which the flexible tube is pre-crushed by said first and second jaws before causing any significant restriction of the flow of fluid therethrough.
- 3. The proportional flow control valve recited by claim 1 wherein said actuator is a ram operated by a pressurized fluid and coupled to one of said first and second jaws for selectively urging one of said first and second jaws toward the other of said first and second jaws.
- 4. The proportional flow control valve recited by claim 3 wherein said control system regulates fluid pressure applied to the pressurized fluid that operates the ram.
- 5. The proportional flow control valve recited by claim 4 wherein the fluid pressure regulated by said control system has a magnitude that is substantially inversely proportional to the flow of fluid through the flexible tube.
- 6. The proportional flow control valve recited by claim 1 including a bias member coupled to said actuator, said bias member applying a force to said actuator tending to increase the separation distance between said first and second jaws.
- 7. The proportional flow control valve recited by claim 6 wherein said bias member includes at least one spring, said spring being compressed when said actuator decreases the separation distance between said first and second jaws.
- 8. The proportional flow control valve recited by claim 7 wherein said bias member includes a plurality of springs, each of said springs being compressed when said actuator decreases the separation distance between said first and second jaws.
- 9. The proportional flow control valve recited by claim 4 including a plurality of springs and a selector, said selector selecting a number of said plurality of springs for being compressed when said actuator decreases the separation distance between said first and second jaws, the selected plurality of springs exerting a biasing force when compressed, the biasing force tending to increase the separation distance between said first and second jaws.
- 10. The proportional flow control valve recited by claim 9 wherein:
a. the pressurized fluid regulated by said control system applies a predetermined shut-off force to the actuator ram when decreasing the separation distance between said first and second jaws to said shut-off separation distance; b. the selected plurality of springs develop a selected biasing force when said actuator changes the separation distance between said first and second jaws from the initial separation distance to the shut-off separation distance; and c. the selected biasing force developed by the selected plurality of springs is commensurate with the predetermined shut-off force applied to the actuator ram.
- 11. The proportional flow control valve recited by claim 1 wherein said actuator is coupled to said first jaw and selectively moves said first jaw relative to said second jaw, the proportional flow control valve further including a first adjustable stop for limiting the degree to which said actuator can advance said first jaw toward said second jaw, and for preventing the flexible tube from being overly crushed.
- 12. The proportional flow control valve recited by claim 11 including a bias member coupled to said actuator, said bias member applying a force to said actuator tending to increase the separation distance between said first and second jaws, the proportional flow control valve further including a second adjustable stop for limiting the degree to which said bias member actuator can force said first jaw away from said second jaw.
- 13. The proportional flow control valve recited by claim 1 wherein separation of said first and second jaws by a separation distance that lies midway between the initial separation distance and the shut-off separation distance results in a flow of fluid of approximately one-half that when said first and second jaws are separated by the initial separation distance.
- 14. The proportional flow control valve recited by claim 1 wherein said control system for controlling said actuator is a pneumatic pressure regulator that applies pneumatic pressure to said actuator, and wherein the pneumatic pressure has a magnitude that is substantially proportional to the flow of fluid through the flexible tube.
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is being filed concurrently with related application Ser. No. ______, entitled “LEVEL CONTROL SYSTEM FOR SHEET CASTING PROCESS,” assigned to the assignee of the present invention, and naming James Edward Ellis as the inventor.