Apparatus and method for dispensing fluid materials using position-dependent velocity feedback

• US 4,842,162 A
• Filed: 03/07/1988
• Issued: 06/27/1989
• Est. Priority Date: 03/27/1987
• Status: Expired due to Term

• Current Assignee: Nordson Corporation
• Original Assignee: Nordson Corporation
• Inventors: Merkel, Stephen L.
• Primary Examiner(s): Huppert, Michael S.
• Assistant Examiner(s): Ammeen, Edward S.
• Application Number:
  US07/164,536
• Time in Patent Office: 477 Days
• Field of Search: 222/1, 222/52, 222/55, 222/61, 222/63, 222/71, 222/146.5, 222/504, 222/559, 901/42, 901/43, 137/8, 137/487.5, 137/805, 137/829, 137/831, 239/67, 239/69, 239/533.1, 239/583, 91/1, 91/361, 91/364
• US Class Current: 222/1
• CPC Class Codes: B05C 5/02 the liquid or other fluent material being discharged through an outlet orifice by pressure, e.g. from an outlet device in contact or almost in contact, with the work
• CPC Class Codes: B05C 5/0225 characterised by flow controlling means, e.g. valves, located proximate the outlet B05C5/0258, B05C5/0275 take precedence; supply valves upstream the coating head B05C11/1036
• CPC Class Codes: G05D 7/0623 characterised by the set value given to the control element
• CPC Class Codes: Y10T 137/0357 For producing uniform flow
• CPC Class Codes: Y10T 137/2071 And causing change or correction of sensed condition
• CPC Class Codes: Y10T 137/2213 Electrically-actuated element [e.g., electro-mechanical transducer]
• CPC Class Codes: Y10T 137/7761 Electrically actuated valve

Abstract

Apparatus and method for dispensing fluid materials wherein the fluid is discharged from a nozzle at a rate controlled by a metering valve having a seat and a stem moveable with respect to the seat to modulate the flow. A servo-actuator connected in a feedback control loop is used to position the valve stem with respect to its seat in accordance with a control signal. The control signal is derived in accordance with the difference between a driving signal representing a desired flow rate and the sum of a pair of feedback signals. One feedback signal represents the actual flow rate while the other feedback signal is correlated to both the relative velocity and position of the stem with respect to the seat. The position-dependent velocity signal is generated by a transducer comprising a magnet and a coil influencable by the field of the magnet as the magnet and coil move relative one another. For any given velocity, the magnitude of the position-dependent velocity signal is greater when the stem and seat are close together than when they are further apart so that as the valve closes, the amount of feedback increases.

Claims

1. An apparatus for dispensing fluid material, comprising:

(a) inlet means for receiving the fluid connectable to a source of fluid;

(b) nozzle means downstream of said inlet means for discharging the fluid;

(c) metering valve means operably disposed between said inlet means and said nozzle means, said metering valve means including a seat and a stem axially moveable relative to the seat to modulate the flow of fluid material;

(d) actuator means connected to said metering valve means for axially shifting said valve stem relative to said valve seat;

(e) first transducer means operably connected to said nozzle means for generating a flow rate signal correlated to the rate of flow of fluid through said nozzle means; and

(f) second transducer means connected to said metering valve stem for generating a position-dependent velocity signal correlated to both the velocity and the position of said stem relative said seat.

2. The apparatus of claim 1 wherein the magnitude of said position-dependent velocity signal increases as the relative velocity between said stem and said seat increases and for any given said relative velocity, said magnitude is greater when the relative distance between said stem and said seat is small than when said distance is larger.

3. The apparatus of claim 2 wherein:

said position-dependent velocity signal is zero when said relative velocity is zero.

4. The apparatus of claim 1 further comprising:

controller means having an output connected to said actuator means for applying a control signal thereto, said controller means having a first input connected to said first transducer means and a second input connected to said second transducer means whereby said control signal is correlated to said flow rate signal and said position-dependent velocity signal.

5. The apparatus of claim 4, further comprising:

driving signal generator means connected to said controller means for generating a driving signal correlated to a desired rate of flow and wherein said control signal is correlated to said flow rate signal, said position-dependent velocity signal and said driving signal.

6. The apparatus of claim 5 further comprising means for combining said driving signal, said flow rate signal and said position-dependent velocity signal so that said control signal is correlated to the difference between said driving signal and the sum of said flow rate signal and said position-dependent velocity signal.

7. The apparatus of claim 1 wherein said second transducer means comprises:

a coil, and

a magnet,

said magnet and said coil being moveable toward and away from one another, the position of said magnet being operatively fixed with respect to one of, said stem and said seat, the position of said coil being operatively fixed with respect to the other of said stem and said seat so that as said stem and said seat move toward one another, said coil is immersed further into the magnetic field associated with said magnet and as said stem and said seat move away from one another, said coil tends to be withdrawn from said magnetic field whereby said position-dependent velocity signal is generated according to the influence of said magnet upon said coil.

8. A method for controlling the flow of a fluid through a nozzle, comprising the steps of:

(a) locating a metering valve in the flow path to said nozzle, said valve and nozzle including a first member moveable relative to a second member to modulate the flow through said nozzle;

(b) generating a position-dependent velocity signal correlated to both the velocity of said first member relative to said second member and the position of said first member relative to said second member;

(c) generating a flow rate signal correlated to the rate of flow of said fluid.

(d) deriving a control signal from at least said position-dependent velocity signal, and said flow rate signal; and

(e) positioning said first member relative said second member in accordance with said control signal to control the flow of the fluid from the nozzle.

11. The method of claim 8 wherein, for a given said velocity, the magnitude of said position-dependent velocity signal increases as the distance between said first member and said second member decreases.

9. A method for controlling the flow of a fluid through a nozzle, comprising the steps of:

(a) locating a metering valve in the flow path to said nozzle, said valve including a first member moveable relative to a second member to modulate the flow through said nozzle;

(b) generating a position-dependent velocity signal correlated to both the velocity of said first member relative to said second member and the position of said first member relative to said second member;

(c) generating a flow rate signal correlated to the rate of the flow of the fluid;

(d) generating a driving signal;

(e) deriving a control signal from at least said position-dependent velocity signal, said flow rate signal, and said driving signal; and

(e) positioning said first member relative said second member in accordance with said control signal to control the flow of the fluid.

10. A method for controlling the flow of a fluid through a nozzle;

comprising the steps of;

(a) locating a metering valve in the flow path to said nozzle, said valve including a first member moveable relative to a second member to modulate the flow through said nozzle;

(b) generating a position-dependent velocity signal correlated to both the velocity of said first member relative to said second member and to the position of said first member relative to said second member;

(c) generating a flow rate signal correlated to the rate of flow of the fluid;

(d) generating a driving signal;

(e) comparing said driving signal to the sum of said flow rate signal and said position-dependent velocity signal to derive a control signal, and

(f) positioning said first member relative said second member in accordance with said control signal to control the flow of the fluid.

12. An apparatus for controlling the flow of a fluid through a flow path, comprising:

(a) metering valve means, said valve means including a first member moveable relative to a second member to modulate the flow;

(b) transducer means connected to said first member of said metering valve means for generating a position-dependent velocity signal correlated to both the velocity of said first member relative to said second member and the position of said first member relative to said second member;

(c) controller means connected to said transducer means for deriving a control signal from at least said position-dependent velocity signal, and

(d) actuator means connected to said controller means and said metering valve means for positioning said first member relative said second member in accordance with said control signal to control the flow of the fluid.

13. An apparatus for controlling the flow of a fluid through a flow path:

(a) metering valve means in the flow path, said valve means including a first member moveable relative to a second member to modulate the flow;

(b) transducer means connected to said first member of said metering valve means for generating a position-dependent velocity signal correlated to both the velocity of said first member relative to said second member and the position of said first member relative to said second member;

(c) flow rate sensor means operatively disposed in the flow path for generating a flow rate signal correlated to the rate of flow of the fluid;

(d) controller means connected to said transducer means and said flow rate sensor means for deriving a control signal from at least said position-dependent velocity signal and said flow rate signal; and

(e) actuator means connected to said controller means and said metering valve means for positioning said first member relative said second member in accordance with said control signal to control the flow of the fluid.

14. An apparatus for controlling the flow of a fluid through a flow path comprising:

(a) metering valve means in the flow path, said valve means including a first member moveable relative to a second member to modulate the flow;

(b) transducer means connected to said first member of said metering valve means for generating a position-dependent velocity signal correlated to both the velocity of said first member relative to said second member and the position of said first member relative to said second member;

(c) flow rate sensor means operatively disposed in the flow path for generating a flow rate signal correlated to the rate of flow of the fluid;

(d) controller means connected to said transducer means and said flow rate sensor means as well as to means supplying a driving signal, said driving signal being correlated to a desired flow rate, said controller means including means for deriving a control signal in accordance with the difference between said driving signal and the sum of said flow rate signal and said position-dependent velocity signal;

(e) actuator means connected to said controller means and said metering valve means for positioning said first member relative said second member in accordance with said control signal to control the flow of the fluid.