Hydraulically driven welding machine with feedback

• US 6,166,349 A
• Filed: 10/05/1999
• Issued: 12/26/2000
• Est. Priority Date: 10/05/1999
• Status: Expired due to Term

• Current Assignee: Illinois Tool Works Inc.
• Original Assignee: Illinois Tool Works Inc.
• Inventors: Crowley, Chad L., Williams, Robert G.
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US09/412,423
• Time in Patent Office: 448 Days
• Field of Search: 219/133, 180/53.1, 180/53.4, 180/53.62, 180/53.8, 290/43, 290/54, 322/1, 322/38
• US Class Current: 219/133
• CPC Class Codes: B23K 9/10 Other electric circuits therefor; Protective circuits; Remote controls

Abstract

A hydraulically driven welding machine employs a closed loop control system for maintaining a constant speed of a generator. A feedback device produces a controlled frequency proportional to the actual generator frequency. The controlled frequency is compared with a reference frequency preset in the machine. Any error between the controlled and referenced frequencies is used to control a proportional flow control valve to regulate the flow of hydraulic fluid through a hydraulic motor that rotates the generator to maintain a constant generator speed under varying welding conditions. The source of the hydraulic fluid may be a hydraulic system of a motor vehicle. In an alternate embodiment, an adjustable orifice produces a pressure drop in the hydraulic system. A change in generator speed changes the pressure drop. The pressure drop is used to control a valve that diverts the proper amount of fluid flow to the hydraulic motor to maintain a constant pressure drop and thus a constant generator speed.

Claims

1. A hydraulically powered welding machine comprising an electrical system that produces electrical energy for one or more welding processes;

and a hydraulic system that drives the electrical system and that responds to a change in a selected parameter of a selected one of the electrical system or the hydraulic system such that the hydraulic system response affects the electrical energy produced for a selected welding process.

2. The hydraulically powered welding machine of claim 1 wherein the hydraulic system responds to a feedback signal that is indicative of a selected parameter of the electrical system.

3. The hydraulically powered welding machine of claim 2 wherein:

a. the electrical system comprises a generator;

b. the selected parameter is a controlled frequency of the electrical system, and the feedback signal is indicative of the controlled frequency;

c. the hydraulic system comprises a hydraulic motor that rotates the generator to produce the electrical energy at the controlled frequency; and

d. the hydraulic motor responds to the feedback signal to affect the controlled frequency.

4. The hydraulically powered welding machine of claim 3 wherein the hydraulic system further comprises a proportional flow control valve that responds to the feedback signal to regulate the hydraulic motor to maintain the electrical energy at the controlled frequency.

5. The hydraulically driven welding machine of claim 3 wherein:

a. the electrical system further comprises a source of a reference frequency; and

b. the hydraulic system further comprises a proportional flow control valve that responds to a difference between controlled frequency and the reference frequency to regulate the hydraulic motor to maintain the electrical energy at the controlled frequency.

6. The hydraulically powered welding machine of claim 1 wherein:

a. the electrical system comprises a generator;

b. the selected parameter is a pressure drop in the hydraulic system;

c. the hydraulic system comprises a hydraulic motor that rotates the generator to produce the electrical energy at a controlled frequency; and

d. the hydraulic motor responds to a change in the pressure drop to affect the controlled frequency.

7. The hydraulically powered welding machine of claim 6 wherein:

a. the hydraulic system further comprises;

i. a pump that supplies hydraulic fluid to the hydraulic motor; and

ii. an orifice interposed between the pump and the motor that produces the pressure drop, the orifice producing a first pressure drop when the pump supplies hydraulic fluid to the orifice and the motor such that the generator produces electrical energy at a first frequency, the orifice producing a second pressure drop when the pump supplies hydraulic fluid to the orifice and motor such that the generator produces electrical energy at a second frequency; and

b. the hydraulic system responds to the second pressure drop to change the supply of hydraulic fluid to the orifice and the motor to return the second pressure drop to the first pressure drop and thereby supply the hydraulic motor with hydraulic fluid such that the generator produces electrical energy at the first frequency.

8. The hydraulically powered welding machine of claim 7 further comprising a diverter valve interposed between the pump and the orifice, the diverter valve responding to a change in the pressure drop across the orifice from the first pressure drop to the second pressure drop to regulate the hydraulic flow through the orifice and the motor to maintain the first pressure drop and thereby maintain the electrical energy at the first frequency.

9. The hydraulically powered welding machine of claim 7 wherein the orifice is adjustable.

10. The hydraulically powered welding machine of claim 7 further comprising safety means for directing hydraulic fluid completely away from the hydraulic motor and thereby stopping the hydraulic motor in response to the generator attaining a predetermined overspeed condition.

11. A hydraulically driven welding machine comprising:

a. a hydraulic motor that drives a generator to produce a predetermined generator output for performing a selected welding operation; and

b. a closed loop control system that senses an actual generator output and utilizes differences thereof from the predetermined generator output to regulate hydraulic fluid flowing from a source thereof through the hydraulic motor to maintain the predetermined generator output.

12. The hydraulically driven welding machine of claim 11 wherein:

a. the predetermined generator output is a predetermined generator speed; and

b. the closed loop control system senses an actual generator speed to regulate the hydraulic fluid flowing through the hydraulic motor to maintain the predetermined generator speed.

13. The hydraulically driven welding machine of claim 11 wherein the closed loop control system comprises a proportional flow control valve that regulates the amount of hydraulic fluid flowing through the hydraulic motor to maintain the predetermined generator output.

14. The hydraulically driven welding machine of claim 12 wherein the closed loop control system comprises:

a. feedback means for producing a controlled signal corresponding to the actual generator speed; and

b. valve means for receiving the controlled signal from the feedback means and for regulating the amount of hydraulic fluid flowing through the hydraulic motor in response to a difference between the controlled signal and a selected reference signal.

15. The hydraulically driven welding machine of claim 14 wherein the valve means comprises a proportional flow control valve interposed between the source of the hydraulic fluid and the hydraulic motor.

16. The hydraulically driven welding machine of claim 14 wherein:

a. the selected reference signal is a preset reference frequency;

b. the controlled signal from the feedback means is a controlled frequency proportional to the actual generator speed; and

c. the difference between the reference frequency and the controlled frequency produces an error that controls the valve means to regulate the amount of hydraulic fluid flowing through the hydraulic motor.

17. Apparatus for performing welding operations comprising:

a. means for presetting a predetermined frequency for a welding operation;

b. generator means for generating welding power at the predetermined frequency;

c. motor means for rotating the generator means at a speed that generates the welding power at the predetermined frequency;

d. electrode means for utilizing the welding power to perform the welding operation at the predetermined frequency;

e. pump means for supplying hydraulic fluid to the motor means;

f. valve means for regulating the fluid flowing from the pump means to the motor means; and

g. feedback means for controlling the valve means to regulate the fluid flowing to the motor means to maintain the predetermined generator frequency regardless of changes in the welding operation.

18. The apparatus of claim 17 wherein:

a. the pump means comprises;

i. a hydraulic pump; and

ii. a motor vehicle having engine and transmission means for driving the hydraulic pump; and

b. the feedback means operates independently of the motor vehicle engine and transmission means.

19. The apparatus of claim 17 wherein the valve means comprises a proportional flow control valve.

20. The apparatus of claim 17 wherein:

a. a reference frequency is fed to a summing junction;

b. the feedback means comprises means for converting the generator speed to a controlled frequency that is fed to the summing junction; and

c. a difference between the reference frequency and the controlled frequency at the summing junction produces an error that controls the valve means to regulate the fluid flowing to the motor means to maintain a generator speed that generates the welding power at the predetermined frequency.

21. A method of controlling a hydraulically driven welding machine comprising the steps of:

a. providing a hydraulic system and an electrical system including a generator;

b. predetermining a value of a selected parameter of a selected one of the hydraulic system and the electrical system;

c. operating the hydraulic system to rotate the generator at a first speed that produces first electrical welding energy while the selected parameter is at the predetermined value thereof;

d. changing the first generator speed to a second speed and simultaneously changing the selected parameter from the predetermined value thereof; and

e. using the change in the selected parameter from the predetermined value thereof to return the generator speed from the second speed to the first speed and simultaneously returning the selected parameter to the predetermined value thereof,

so that the welding machine maintains producing the first electrical welding energy.

22. The method of claim 21 wherein:

a. the step of predetermining a value of a selected parameter comprises the step of setting a predetermined reference frequency of the electrical welding energy suitable for a selected welding process;

b. the step of operating the hydraulic system comprises the step of rotating the generator to produce the electrical welding energy at a controlled frequency;

c. the step of changing the first generator speed comprises the step of changing the controlled frequency; and

d. the step of using the change in the selected parameter comprises the steps of;

i. comparing the controlled frequency with the reference frequency; and

ii. changing the second generator speed in response to a difference between the controlled frequency and the reference frequency to return the generator speed to the first speed and thereby maintaining the controlled frequency of the electrical welding energy substantially equal to the reference frequency.

23. The method of claim 22 wherein:

a. the step of operating the hydraulic system comprises the steps of;

i. connecting the generator rotor to a hydraulic motor; and

ii. flowing hydraulic fluid from a source thereof through the hydraulic motor and thereby rotating the motor and the generator rotor; and

b. the step of changing the first generator speed comprises the steps of;

i. interposing a proportional flow control valve between the source of the hydraulic fluid and the hydraulic motor; and

ii. controlling the proportional flow control valve to regulate the flow of hydraulic fluid through the motor in response to the difference between the controlled frequency and the reference frequency.

24. The method of claim 21 wherein:

a. the step of predetermining a value of a selected parameter comprises the step of setting a predetermined pressure drop within the hydraulic system;

b. the step of operating the hydraulic system comprises the step of rotating the generator at the first generator speed and simultaneously producing the predetermined pressure drop;

c. the step of changing the first generator speed comprises the step of changing the pressure drop from the predetermined value thereof to a second value; and

d. the step of using the change in the selected parameter comprises the step of using the change in the pressure drop to return the pressure drop from the second value to the predetermined value thereof and simultaneously returning the generator speed to the first generator speed.

25. The method of claim 24 wherein:

a. the step of providing a hydraulic system comprises the steps of providing a hydraulic motor that drives the generator, and an orifice that directs hydraulic fluid to the hydraulic motor;

b. the step of setting a predetermined pressure drop comprises the step of setting a predetermined pressure drop across the orifice in response to the generator rotating at the first generator speed; and

c. the step of using the change in the pressure drop comprises the step of changing hydraulic fluid flow to the orifice and the hydraulic motor in response to a change in the predetermined pressure drop across the orifice.