Control system for metering pump and method

• US 6,517,891 B1
• Filed: 10/31/2000
• Issued: 02/11/2003
• Est. Priority Date: 10/31/2000
• Status: Expired due to Term

• Current Assignee: Nordson Corporation
• Original Assignee: Nordson Corporation
• Inventors: Saidman, Laurence B., Estelle, Peter W.
• Primary Examiner(s): Bareford, Katherine A.
• Application Number:
  US09/702,427
• Time in Patent Office: 833 Days
• Field of Search: 427/8, 427/421, 427/424, 222/63
• US Class Current: 427/8
• CPC Class Codes: B05B 12/085 responsive to flow or pressure of liquid or other fluent material to be discharged B05B1/3006, B05B1/323, B05B7/1254 take precedence
• CPC Class Codes: F04B 13/00 Pumps specially modified to deliver fixed or variable measured quantities
• CPC Class Codes: F04B 49/20 by changing the driving speed
• CPC Class Codes: Y10T 156/1798 with liquid adhesive or adhesive activator applying means

Abstract

An apparatus for controlling a speed of a motor of a metering pump providing pressurized fluid at a dispensing gun. The dispensing gun is opened and closed to dispense fluid onto a substrate being carried by a conveyor past the dispensing gun. The apparatus has a pressure control producing first motor speed signals as a function of changing speeds of the conveyor and changing fluid pressures in the dispensing gun when the dispensing gun is open. A flow control produces second motor speed signals as a function of the changing speeds of the conveyor. During changes in conveyor velocity, a motor speed control provides the first motor speed signal to the pump motor which operates the motor at speeds causing the pump to provide fluid to the dispensing gun at pressures changing at a rate tracking a rate of change of the speed of the conveyor. When full conveyor speed is detected, the motor speed control provides the second motor speed signal to the pump motor which operates the motor at speeds determined by the full conveyor speed. In addition, there are methods for generating pressure related and conveyor speed related motor speed signals and automatically switching between those signals as a function of the conveyor speed.

Claims

1. A method of providing fluid under pressure to a dispensing gun with a metering pump connected to a motor, the dispensing gun being opened and closed to dispense fluid onto a substrate being carried by a conveyor past the dispensing gun, the method comprising:

changing a conveyor speed at a rate of change;

detecting pressures of the fluid at the dispensing gun while the conveyor speed is changing and the dispensing gun is dispensing fluid;

detecting conveyor speeds;

changing a pressure of the fluid at the dispensing gun in response to detecting the pressures and the conveyor speeds, so that the pressure of the fluid at the dispensing gun changes at a rate tracking a rate of change of the conveyor speed;

detecting a full conveyor speed; and

thereafter automatically controlling a flow of the fluid at the dispensing gun as a function of only the full conveyor speed.

2. The method of claim 1 wherein the step of automatically controlling a flow of the fluid at the dispensing gun further comprises:

detecting a desired operating pressure of the fluid at the dispensing gun at the full speed of the conveyor.

3. A method of providing fluid under pressure to a dispensing gun with a motor connected to a metering pump, the dispensing gun being opened and closed to dispense fluid onto a substrate being carried by a conveyor past the dispensing gun, the method comprising:

changing a conveyor speed at a rate of change;

determining pressures of the fluid at the dispensing gun while the speed of the conveyor is changing and the dispensing gun is dispensing fluid;

determining conveyor speeds;

generating first motor speed signals in response to the pressures and the speeds;

changing a pressure of the fluid at the dispensing gun by controlling the speed of the motor as a function of the first motor speed signals, so that the pressure of the fluid at the dispensing gun changes at a rate tracking a rate of change of the conveyor speed;

detecting a full conveyor speed; and

then

automatically switching control of the speed of the motor from the first motor speed signals to second motor speed signals representing only the full conveyor speed.

4. The method of claim 3 further comprising:

providing a sampled speed of the conveyor;

generating a target pressure as a function of the sampled speed;

providing a sampled pressure of the fluid at the dispensing gun; and

determining the first motor speed signal as a function of the target pressure and the sampled pressure.

5. The method of claim 4, wherein generating the target pressure further comprises multiplying the sampled speed times a stored constant, the stored constant representing a fraction having a numerator representing a pressure at the dispensing gun and a denominator representing a conveyor speed.

6. The method of claim 4 wherein generating the target pressure further comprises multiplying the sampled speed times a stored constant, the stored constant representing a fraction having a numerator representing a desired dispensing pressure at the dispensing gun during a dispensing operation and a denominator representing a full speed of the conveyor.

7. The method of claim 4 wherein generating the target pressure further comprises multiplying the sampled speed times a stored constant, the stored constant representing a fraction having a numerator representing a full pressure at the dispensing gun at full conveyor speed of the during an immediately prior dispensing operation and a denominator representing a full conveyor speed during the immediately prior dispensing operation.

8. The method of claim 4 further comprising determining the first motor speed signal by utilizing the target pressure and the sampled pressure in a proportional, derivative, integral process loop.

9. A method of providing fluid under pressure to a dispensing gun with a motor connected to a metering pump, the dispensing gun being opened and closed to dispense fluid onto a substrate being carried by a conveyor past the dispensing gun, the method comprising:

increasing a conveyor speed from rest to a full conveyor speed at a rate of change;

detecting a sampled pressure of the fluid at the dispensing gun while the speed of the conveyor is increasing and the dispensing gun is dispensing fluid;

detecting a sampled conveyor speed;

generating a first motor speed signal in response to the sampled pressure and the sampled conveyor speed;

changing a pressure of the fluid at the dispensing gun by controlling the speed of the motor in response to the first motor speed signal, so that the pressure of the fluid at the dispensing gun changes at a rate tracking the rate of change of the conveyor speed;

detecting a full conveyor speed; and

then

automatically switching control of the speed of the motor from the first motor speed signal to a second motor speed signal representing only the full conveyor speed.

10. The method of claim 9 wherein the step of switching control of the speed of the motor further comprises:

detecting a target pressure of the fluid at the gun at a full conveyor speed; and

generating the second motor speed signal in response to detecting the target pressure of the fluid at the gun at the full conveyor speed.

11. The method of claim 10 further comprising generating a plurality of motor speed command signals as a function of a combination of the first and second motor speed signals, each successive motor speed command signal being generated with successively smaller portions of the first motor speed signal and successively larger portions of the second motor speed signal.

12. The method of claim 11 further comprising:

generating initial motor speed command signals as a function of principally the first motor speed signal;

generating successive motor speed command signals as a function of successively smaller portions of the first motor speed signal and successively larger portions of the second motor speed signal; and

generating final motor speed command signals as a function of principally the second motor speed signal.

13. The method of claim 11 further comprising generating motor speed command signals in accordance with

14. The method of claim 9 further comprising:

generating a target pressure by multiplying the sampled speed times a stored constant, the stored constant representing a fraction having a numerator representing a pressure at the dispensing gun and a denominator representing a conveyor speed; and

determining the first motor speed signal as a function of the target pressure and the sampled pressure.

15. The method of claim 14 wherein generating the second motor speed signal further comprises multiplying the sampled speed times a stored constant, the stored constant representing a fraction having a numerator representing a motor speed and a denominator representing a conveyor speed.

16. The method of claim 9 further comprising:

generating a target pressure by multiplying the sampled speed times a stored constant, the stored constant representing a fraction having a numerator representing a desired dispensing pressure at the dispensing gun during a dispensing operation and a denominator representing a full speed of the conveyor; and

determining the first motor speed signal as a function of the target pressure and the sampled pressure.

17. The method of claim 16 wherein generating the second motor speed signal further comprises multiplying the sampled speed times a stored constant, the stored constant representing a fraction having a numerator representing a full motor speed during a fluid dispensing operation and a denominator representing a full speed of the conveyor.

18. The method of claim 9 further comprising:

generating a target pressure by multiplying the sampled speed times a stored constant, the stored constant representing a fraction having a numerator representing a full pressure at the dispensing gun at full conveyor speed of the during an immediately prior dispensing operation and a denominator representing a full conveyor speed during the immediately prior dispensing operation; and

determining the first motor speed signal as a function of the target pressure and the sampled pressure.

19. The method of claim 18 wherein generating the second motor speed signal further comprises multiplying the sampled speed times a stored constant, the stored constant representing a fraction having a numerator representing a full motor speed at full conveyor speed during an immediately prior dispensing operation and a denominator representing a full conveyor speed during the immediately prior dispensing operation.

20. The method of claim 19 further comprising generating motor speed command signals in accordance with

21. The method of claim 9 further comprising:

decreasing the speed of the conveyor from a full conveyor speed to rest at a rate of change;

generating the first motor speed signal in response to the sampled pressure and the sampled conveyor speed;

changing the speed of the motor in response to the first motor speed signal while the conveyor speed is decreasing and changing the pressure of the fluid at the dispensing gun at a rate tracking the rate of change of the speed of the conveyor;

detecting a pressure being equal to a recirculation pressure; and

then

automatically switching control of the speed of the motor from the first motor speed signal to a motor speed signal representing a recirculation mode.