Abstract: During a weld period the weld parameters are monitored and data representing the weld resistance curve and the power curve are acquired and stored for analysis by a suitably programmed computer. The derivative of R, R is calculated and stored and the function is divided by power P to obtain R/P. The resistance curve is searched to obtain the maximum value R.sub.m which occurs during the heating phase and the function R/P is searched prior to the time of R.sub.m to find the maximum of that curve representing the highest rate of resistance increase. Then the R/P curve is searched subsequent to its maximum to determine when the function reaches a specified percentage of the maximum. That value occurs at the knee of the resistance curve and approximates the onset of melting in the weld.

Abstract: A computer-controlled welding apparatus includes a phase-controlled resistance welding circuit (A) for selectively conducting pulses of a welding current to a workpiece (B) and a control circuit (C) for controlling the conduction of the welding current. The control circuit includes a line clock generator (30) for determining the beginning of each voltage half line cycle and a conduction sensor (34) for determining whether or not a contactor (14) is conducting current to the workpiece. A microcomputer (40) is preprogrammed with a plurality of power factor correction curves, each of which represents weld current vs. firing angle for a fixed hangover angle. The computer is programmed to select one of the power factor correction curves. If the preceding half line cycle was conductive, the program selects the curve which corresponds to the hangover angle of the preceding half line cycle.

Abstract: The apparatus comprises a current transformer coupled to the welding tranrmer primary and connected with an analog transmitter of the welding current and with a digital transmitter of the duration of short-circuits in the welding circuit, having a memory element at the output.

Abstract: During a weld period the weld parameters are monitored and data representing the weld resistance curve and the power curve are acquired and stored for analysis by a suitably programmed computer. The derivative of R, R is calculated and stored and the function is divided by power P to obtain R/P. The resistance curve is searched to obtain the maximum value R.sub.m which occurs during the heating phase and the function R/P is searched prior to the time of R.sub.m to find the maximum of that curve representing the highest rate of resistance increase. Then the R/P curve is searched subsequent to its maximum to determine when the function reaches a specified percentage of the maximum. That value occurs at the knee of the resistance curve and approximates the onset of melting in the weld.

Abstract: An instrumented spot welding electrode significantly improves the weld quality available from production resistance spot welding machines by providing real time measurements of key multivariable resistance welding parameters. The real time data provided may be used as inputs to adaptively control welding machines and dynamically adjust welding system operation responsive to the sensed variables. A number of sensors are positioned within a cavity specially formed into a water cooled electrode tip to obtain the desired measurements while being protected against physical damage. The sensors are advantageously placed in good thermal and electrical contact with a plug element which bears directly on the workpieces being welded to enhance the accuracy of the sensed variables. This specially configured and instrumented sensor cavity is ideally suited for use with all end types of electrodes including spherical, truncated, offset, flat and the like.

Abstract: The thickness of the molten weld nugget is continuously monitored during resistance spot welding, and when proper penetration is achieved the applied current is turned off. An ultrasonic transducer housed in the water cooled lower welding electrode transmits ultrasonic pulses into the workpiece and receives waves reflected at each solid/solid and liquid/solid interface. The position of the latter is tracked by pulse time discrimination of reflected signals; weld nugget penetration is computed using a ratio of times or a pulse time difference.

Abstract: A monitoring circuit for an a.c. resistance welding apparatus for can bodies is arranged to produce an output signal which is representative of the integral with respect to time of the resistive or in-phase component of the welding voltage taken over the half-cycles of welding current. The output signal is representative of the energy expended during welding, and may be used for indication or control.

Abstract: A method and system for determining weld quality in resistance welding in such a manner that acceptance or unacceptance is determined by comparing with their respective reference values the electrode voltage, the electrode current time, the number of electrode voltage pulse signals in excess of the reference value, and the integral of difference between the electrode voltage in excess of a base voltage and the base voltage, independently or simultaneously, in addition to the comparison of the electrode resistance with its reference value. The relatively low-priced system according to the present invention can determine weld quality accurately even when the electrode tips are deformed or crushed so as to form other current path areas.

Abstract: The quality of an electrical resistance spot weld is determined by monitoring the squeezing force applied through the electrodes to the workpieces by a force-transmitting device that exerts a squeezing force that varies when indentation of the workpieces occurs.

Abstract: In an electrical spot welding machine having sensor leads for monitoring weld nugget resistance connected to the electrodes or to the welding current conductors, the voltage component induced in the sensor leads due to inductive coupling is cancelled out by inducing a substantially equal and opposite compensating voltage in the sensor leads. For this purpose an inductance coil may be connected into one of the sensor leads and appropriately positioned on one of the welding current conductors. A core-less coil can be employed, and correct adjustment of the compensating voltage can be achieved by adjusting the coil angularly with respect to the axis of the welding current conductor.

Abstract: A method for detecting whether dissimilar metals or alloys are being welded together is disclosed. Metals or alloys are welded together and electrical leads connected to a multi-purpose potentiometer or a voltmeter contact each metal at points heat conductively remote from the weld. The arrangement performs as a thermocouple with the weld acting as the "hot junction" and the contact points remote from the weld being at substantially ambient temperature, and acting as the "cold junction." According to the thermoelectric laws, if the metals are dissimilar, a current and EMF result provided that the hot junction and the cold junction are at different temperatures. If the metals are similar, no signal is generated. The potentiometer or the voltmeter detects whether any electrical signal is present. In the same manner, an unknown metal may be positively identified by welding it to different reference metals until no signal is generated.

Abstract: An electrode tip for electric spot welding is formed with a hole which extends from one side of the tip to the end surface of the tip and is arranged to receive one end of a radiant energy conveyor which is intended to transmit a signal indicative of the temperature reached at the end surface of the tip. An insert is fitted within the hole with interference and arranged adjacent to the end surface of the tip in order to ensure the continuity of the said end surface.

Abstract: A control system for use with a welding machine controller is provided which senses the dynamic resistance of the weld being formed by the welding machine, and which generates appropriate signals indicating the condition of the weld, which signals may be used for automatically controlling the operation of the controller. The control system of the invention senses the power factor in the primary circuit of the welding transformer included in the welding machine which is a measure of the dynamic resistance of the weld being formed, and the control system produces signals indicating the dynamic resistance of the weld, which signals may be digitized to produce appropriate control signals for the controller.

Abstract: To measure the relative power during a welding process, a position sensitive transducer is attached to a welding electrode to submit a signal in response to electrode motion. An accelerometer, carried on an axle of an electrode roll for a Soudronics pulse type resistance welder, will emit a signal indicative of the quality of the weld. The accelerometer measures the forging taking place during welding by means of its position sensitivity and the amount of forging has been found to be a function of the characteristics of the weld.

Abstract: A signal emitted from a transducer responsive to the relative power applied during a welding process is enhanced electronically and mathematically to be of use in controlling welder operating parameters and/or in rejecting defective welds. Electronically the signal refined to minimize unnecessary noise in the signal and mathematically the signal is modified and analyzed against a standard. In a high speed welding operation automatic means are necessary to assure weld quality and control welder operation since the rapidity with which the welding takes place is too fast for manual readjustment.

Abstract: A controller for a spot-welding machine compares the temperature evolution at a site at which a spot weld is being made to a standard thermal history stored in a digital read/write memory in controlling the welding current for the weld. Standard thermal histories can be generated and written into the memory as needed by an operator of the welding machine to take into account changes in operating conditions. The temperature evolution of the spot-welding operation is monitored by detecting radiant energy whose intensity provides a measure of a temperature of the weld. Phosphorescent radiation from a thermographic phosphor located in a welding tip of the welding machine and thermal infrared radiation are preferred for monitoring the temperature evolution of the spot-welding operation.

Abstract: An electrical resistance spot welding system and method is disclosed. The system has adjustable output power circuitry for applying electrical heating energy to a weld site by way of weld tips, in accordance with a welding operation. An energy monitor senses instantaneous accumulated energy applied during the welding operation, and terminates the operation when an adjustable predetermined total energy has been applied. Other circuitry monitors applied welding voltage, and derives therefrom a signal which is a function of the energy density per unit area applied at the weld site. Circuitry responds to the energy density sensing to control the energy monitor and the power circuitry to govern the total energy applied in the welding operation.

Abstract: An apparatus for monitoring and controlling a welding phenomenon in an electric resistance welding process, which comprises a welding characteristics measuring instrument for carrying out digital measurement of at least one of high frequency welding characteristics, a welding phenomenon monitor circuit for detecting variations in the welding characteristics, and a welding phenomenon controller circuit for automatically adjusting a parameter of a welding power source or other welding conditions, wherein the welding characteristics include an oscillating frequency and an oscillating period of a high frequency used for the welding, and a phase difference between a high frequency voltage and a current. Changes in the welding characteristics occur in correspondence with the occurrence of periodic fluctuations in the shape of the high frequency welding current circuit formed in the material to be welded during high frequency electric resistance welding process.

Abstract: An improved weld monitoring apparatus and a method for its use are disclosed. Specifically, the invention relates to the application of integrating voltmeters to the monitoring of a resistance seam welding process applicable to cans and the like, wherein a blanking pulse generator is used to direct a voltage signal from the welding process to suitably adapted integrating voltmeters.

Abstract: An ultrasonic vibrator disposed on one of two opposed electrodes having two metallic plates sandwiched between them for being welded intermittently delivers a pulse-shaped ultrasonic wave to a reflecting surface located in the other electrode and receives the wave reflected from the reflecting surface. The vibrator converts the received wave to an electrical signal that is applied to a minimum sensor and a peak sensor. The minimum sensor senses and holds the minimum peak magnitude of the signal which is then subtracted from the peak magnitude of a similar signal developed within the peak sensor at the time of termination of the welding current. The resulting difference between the two magnitudes determines the weld condition of the welded plates.

Abstract: To provide a plurality of different weld quality indicators in resistance, projection and forge welding, the varying separation of two electrodes during a plurality of different time brackets defined within a weld cycle is measured. At least one interval timer is used to define such time brackets. These weld quality indicators include the surface resistance of the workpieces, the melting rate, the maximum expansion, the expansion rate, the weld size, the forge force, the set-down rate, etc.

Abstract: A resistance spot welding method and apparatus wherein a weld can be judged to have an acceptable strength whether a splash (expulsion of weld metal) has occurred or not, provided that a maximum displacement (M) of a movable electrode to a fixed one is larger than a certain predetermined reference value (M.sub.L) or a rate (R) of the displacement at an initial stage is larger than a certain predetermined reference value (R.sub.L) which is defined between two certain predetermined reference values (R.sub.1, R.sub.E), by sensing the displacement and the rate thereof. Furthermore, when necessary, a weld is judged to have an acceptable indentation (I), as well, by sensing a position of the electrode at a specific point of time when a predetermined holding time has elasped from the time of de-energization of the welding current. Thus reliability of a spot welded joint is much improved and costly rejection of a welded product is considerably reduced.

Abstract: A machine and method terminating armature windings to commutators having means for testing the integrity of the connection and winding between two commutator segments immediately after each termination is bonded and recycling the bonding sequence at the same or different bonding energy if certain faults are detected. If the tests indicate certain faults or retests are negative, the armature is ejected without making further termination.