Pressure welding with closed loop force control

• US 5,138,127 A
• Filed: 07/31/1991
• Issued: 08/11/1992
• Est. Priority Date: 07/31/1991
• Status: Expired due to Term

• Current Assignee: Amada Miyachi America, Inc. (Amada Company Limited)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Hill, William H., Fries, William M., Donner, Joseph E., Ratledge, Thomas L.
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US07/738,390
• Time in Patent Office: 377 Days
• Field of Search: 219/110, 219/56.21, 219/109, 219/86.51, 219/86.32, 228/8
• US Class Current: 219/86.51
• CPC Class Codes: B23K 11/318 Supporting devices for electrode holders

Abstract

A parallel-gap welder applies a precisely controlled force to the weld head (40) by means of a solenoid (60) having a plunger (72) aligned with the axis of the welding electrodes (50,52). To precisely control the amount of force applied by the solenoid a load cell (80) is interposed between the weld head (40) and the solenoid plunger (72) to provide a feedback force signal (158) indicative of the force applied by the solenoid. The feedback force signal is used to control current through the solenoid coil (68) and thereby servo the applied force to a force command input. The solenoid plunger (72) and load cell (80) are axially aligned with the axis of the electrodes (50,52) and solenoid force is applied through a universal joint (76,78) connection to assure an in-line driving force on the electrodes.

Claims

1. Pressure welding apparatus comprising:

a weld head support,

a weld head movably mounted to the support,

means for moving the weld head relative to the weld head support toward and away from a work piece to be welded,

electrode means carried by the weld head and adapted to be pressed against a workpiece to be welded,

drive means for applying force to said weld head to thereby cause said electrode means to press against a workpiece, wherein said drive means includes a solenoid coil,

pressure sensing means interposed between said drive means and said weld head for generating a force signal representative of force applied by said drive means, wherein said pressure sensing means includes a load cell generating said force signal,

feedback means responsive to said force signal for controlling said drive means and for generating a command signal,

a difference circuit responsive to said force signal and to the command signal for generating an error signal,

current control means in circuit with said solenoid coil and responsive to said error signal for controlling current in said solenoid coil in accordance with said force signal, and

means for controlling the axial direction and alignment of the drive means and the weld head comprising ball and socket means between said solenoid and said load cell.

2. A parallel-gap welder comprising:

a support,

a carriage slide mounted to the support for vertical motion,

means for driving the carriage slide relative to the support,

a slide body fixed to the slide and having a forwardly extending upper arm, said upper arm having an internally threaded aperture extending therethrough,

a solenoid having a housing, a solenoid coil and a solenoid plunger extending through the solenoid and through the carriage upper arm,

a connector fitting fixed to the housing and threadedly engaged with said threaded aperture,

means for feeding electric current to said coil,

a weld head positioned beneath said upper arm,

first and second mutually spaced parallel spring strips having opposite ends thereof respectively fixed to said weld head and to said carriage slide, whereby said weld head is flexurally mounted to and carried by said carriage slide for a limited amount of displacement relative to the carriage slide,

first and second touch-down contacts mounted respectively on said weld head and carriage slide and being in contact with one another in a normal position of said weld head relative to said carriage slide, said contacts being separated from one another upon displacement of said weld head relative to said carriage slide,

a load cell interposed between said solenoid plunder and said weld head for generating a force signal representative of force applied by said solenoid plunger,

a pair of welding electrodes carried by said weld head in alignment with said solenoid plunger,

feedback means responsive to said force signal for controlling said solenoid plunger and for generating a command signal,

a difference circuit responsive to said force signal and to the command signal for generating an error signal,

current control means in circuit with said solenoid coil and responsive to said error signal for controlling current in said solenoid coil in accordance with said force signal,

means for controlling the axial direction and alignment of the solenoid and the load cell comprising ball and socket means between said solenoid and said load cell, and

means for conducting electrical current to said electrodes.

3. The welder of claim 2 including closed loop feedback means responsive to said load cell for controlling said electric current to said coil.