Unitek

Unitek Equipment Inc.

Gerald Dufrenne

A fast response weld head which employs a control system to allow user control of critical welding parameters such as speed, force, position, and duration. In one embodiment, the control system includes a position servo loop attached to a motor driven output shaft on which a welding electrode is mounted utilizing a follow-up spring assembly. During a weld cycle, the control system moves the welding electrode toward a workpiece at a rapid user-defined rate. Just prior to when the electrode is reduced to prevent damage to the parts. When contact is made, the force exerted by the electrode on the workpiece is measured until the measured force equals a user-defined optimum welding force. A user-defined weld current is enabled to the electrode. When the weld is complete, the welding electrode is automatically raised by the control system, releasing all pressure on the workpiece. In a second and presently preferred embodiment, a linear magnetic actuator is utilized in lieu of a motor to drive the output shaft. The follow-up spring assembly is eliminated. The force required to keep constant pressure on the weld is now provided by programming the linear actuator to exert a very short pulse of force to maintain constant pressure on the weld as the weld softens at the onset of applications of weld current. Force is then returned to normal force until the weld is complete.

Fast response weld head

The motorized weld head employs a control system which allows user control of critical welding parameters such as speed, force, position, and duration. The control system includes a position servo loop attached to a motor-driven output shaft on which a welding electrode is mounted via a spring. During a weld cycle, the control system moves the welding electrode toward a workpiece at a rapid user-defined rate. Just prior to when the electrode contacts the workpiece, the speed of the electrode is reduced to prevent damage to the parts. When contact is made, a pressure transducer measures the force exerted by the electrode on the workpiece. A comparator continuously monitors the force measured by the transducer and changes state when the measured force equals a user-defined optimum welding force. A signal is then passed to the servo loop commanding it to hold the position of the electrode effectively maintaining the applied force on the workpiece. When mechanical vibrations diminish, a user-defined weld current is enabled to the electrode. After the weld current is fired, the constant force is maintained until the weld cools. Finally, the welding electrode is automatically raised by the control system, releasing all pressure on the workpiece.

Motorized weld head

An apparatus and method for monitoring weld quality and for establishing a proper amount of weld energy and the upper and lower limits of the proper weld energy to be supplied by a precision resistance welding apparatus in order to produce acceptable welds. In the present apparatus and method the difference between the change in voltage and current supplied to a test weld is compared to a reference weld and this difference is used to obtain the upper and lower limits of the proper amount of energy to be supplied by the welder in a production context.

Apparatus and method for monitoring weld quality

An electrically heated thermode mounts to a support movable to position the thermode for multiple lead reflow soldering and includes a flat resistance element folded on its flat side in a U-shape structure in which the bight portion forms the pressing portion and the legs the terminal portions of the thermode. To overcome a problem arising where a group of joints to be soldered have varying height tops, the way in which the thermode is mounted to the movable support provides freedom of rotational movement of the thermode relative to the support while providing a low resistance electrical connection between support and the thermode terminal portions. To overcome a problem arising because opposite end joints sink more heat than interior joints, terminal plates are shaped and connected to the terminal portions so as to distribute a sheet of current in a way that more of the current flows along side edges than along the interior portion of the U-shaped structure.

Titiable electric thermode for multiple connection reflow soldering

Apparatus provides for measuring weld resistance of each of a group of weld sites that are subject to variation with respect to weld resistance. The apparatus includes circuitry for inducing a flow of alternating current in a weld site. The magnitude of the induced alternating current is substantially constant; in particular, the percentage variation in its magnitude is substantially less than the percentage variation in resistance to which the weld sites are subject. The apparatus further includes voltage responsive circuitry for producing a signal representative of the magnitude of the resistance of the weld site.

Weld resistance measuring apparatus for a spot welder

A direct current pulse welder including circuitry for controlling the amount of electric energy delivered to the weld site. By means of feedback techniques the output impedance of the welder is adjusted and changed by utilizing a voltage feedback signal and a current feedback signal to match the impedance of the weld site. Matching the impedance of the welder to the impedance of the weld site enables the welder to deliver the correct amount of power desired to each weld regardless of variations in actual impedance of the weld sites that occur in actual production situations.

Direct current pulse welder

A welding power supply that includes a combination of series and shunt regulating circuits controlled by a single controller, in the charging circuit for a welding energy storage capacitor. The series circuit, which includes a series thyristor, regulates the supply of charging energy to the capacitor from a full wave rectified power source. The series circuit also phases forward to replenish charge lost by leakage by controlling the thyristor firing angle as a function of the difference between the capacitor charge and a pre-selected value. The shunt regulating circuit utilizes a shunt thyristor coupled to the output of the power source to divert energy delivery away from the energy storage capacitor when a preselected charge level on the capacitor is reached. The shunt regulating circuit shorts out the unneeded balance of the charging cycle thereby eliminating capacitor voltage overshoot during the charging process.

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LaVerne, CA, United States of America

Gerald Dufrenne