Abstract: A frequency transducer for monitoring frequency in a power line wherein a frequency representative signal is generated which is twice the frequency of the signal to be monitored in the power line, the frequency representative signal is shaped into a triggering output signal which is supplied as one input to a comparator in a comparator/timer circuit. A second input to the comparator is provided by a timing circuit which produces a reference signal as that second input, said reference signal having a constant non-zero duration, the magnitude of which is dependent upon the timing constant of a resistive-capacitive circuit; said resistive-capacitive circuit being charged by a constant charging current of high value to ensure that variances in the timing constant due to temperature, humidity, contamination and the like are small when considered as a percentage figure.

Abstract: A power factor monitoring and control system for controlling the quality of a spot weld made by assembly line welders. The control system of the present invention detects a change in the load power factor as the weld is formed which is manifested as a change in the current extinction angle of the half cycles of weld current. The time interval between the instant weld current is extinguished at the end of a programmed half cycle and an instant when current is extinguished at the end of a subsequent half cycle provides a measure of the resistance across the weld nugget. The time interval information is stored and compared with information provided during a previous half cycle to generate a difference signal. The change in resistance in the secondary circuit is reflected through the transformer to the transformer primary circuit as a decrease in power factor.

Abstract: This disclosure depicts a novel multiple position electric pushbutton switch. The novel switch comprises a cam and a movable contact assembly having at least two spring elements, each having an electrical contact and a cam-engaging portion. The switch further comprises at least two stationary electrical contacts for contacting the electrical contacts of the movable contact assembly. A housing is provided for containing the cam, the movable contact assembly and the stationary contacts. As the cam is depressed and moved downward into the housing, the cam engages one of the spring elements of the movable contact assembly causing the electrical contact on the spring element to contact a corresponding stationary electrical contact.

Abstract: A solid state overload relay protective apparatus for electric motors which includes not only the overload feature, but the additional features of underload and single phase protection. Small current transformers for sensing the current flow in each phase of the motor are utilized, like those found in the ground fault sensing art because a current-to-voltage converter circuit reflects a short circuit back to the secondary of the transformers. The signal from the current transformers which is proportional to the sensed current in the motor is fed through the converter, a scaling and summing amplifier adjustable for a wide range of motor full load currents, an ideal diode peak detector, a time integrator amplifier, to one input of a comparator circuit having a trip reference voltage signal at another input. The comparator provides an output signal to a transistorized trip level circuit that deenergizes a coil of an overload relay opening its contacts and interrupting power to the motor.

Abstract: An anti-telegraph circuit for locking out the circuit controlling the flow of direct current in a coil winding of an electromagnetically operated switching device, such as a contactor, from an alternating current source whenever improper control voltages are present which would cause repeated operations of the armature picking up and falling out of its sealed position.

Abstract: A solid-state, multistage temperature controller for automatically controlling the operation of fans to maintain the temperature of an associated engine within preselected limits.

Abstract: A selector switch assembly includes modular switch units that are serially-arranged in a housing and are operated by a single rotatable control member that is biased to a first position by a biasing unit. A modular switch unit includes a housing that has an end wall and two opposite sidewalls that each have two recesses at opposite ends which receive planar blade portions of switches to define an enclosure. The control member includes a hollow tube that has a friction member which has cams on the periphery to actuate the switches and also has an opening for frictionally engaging a rotatable adjusting screw on the next modular switch unit. The modular units are sealed into a support and the hollow tube provides access to the adjusting screw outside the support.

Abstract: An adjustable speed pumping system includes a plurality of pumps respectively driven by variable speed A.C. motors each having a power recovery circuit. Each power recovery circuit includes a series connected rectifier bridge, an inductive reactor and an inverter coupled to the secondary winding of the motor which has an A.C. source connected to the primary winding. A fault clearing mechanism is included in each circuit and includes solid state switches in the bridge actuated by a current level sensor coupled to the inverter output. The power recovery circuit also includes current foldback circuitry and secondary gating circuitry coupled to thyristors in the inverter. The power recovery circuits can be connected in parallel with a single motor and the system includes circuitry for sensing the highest amplitude current in the parallel circuits and controlling all circuits with this current.

Abstract: A circuit for controlling operation of an electromagnet includes a source of voltage connectable to the electromagnet to produce current flow in one direction and develop a magnetic force therein. A dissipating circuit is connectable to the electromagnet to form a closed loop and has impedance means for dissipating stored energy with gate means between the closed loop and the source producing current flow from the source through the closed loop when the residual potential drops to the potential of source and produce reverse current flow through the magnet. The circuit also has a reverse current limiting means in parallel with the impedance means and includes a manually variable resistor to adjust the limit of reverse current flow.

Abstract: A power factor monitoring and control system with line disturbance immunity for controlling the quality of spot welds made by resistance welding techniques such as those used in the automotive industry on assembly line welders. As is commonly known, quality and strength of a spot weld can be correlated to a change in resistance measured through the weld as the weld progresses during the fusion progress. This change in resistance in the secondary circuit reflects back through the transformer to its primary circuit as a change in power factor. The timing changes resulting from the change in power factor are sensed by the control circuitry of this system to generate signals which are used by an 8-bit microprocessor properly programmed to operate on the signal information. By determining the amount of increase or decrease that has occurred in the current conduction angle during a group of welds, a basis for the control of the welding heat is obtained.

Abstract: An automatic voltage compensation control for a microprocessor controlled resistance welder system includes a digital voltmeter for measuring the line voltage cycle by cycle and associated circuitry to compensate the welding current in response to the measured line voltage in a manner which tends to hold the welding current constant and independent of line voltage variations. The digital voltmeter consists of a voltage-to-frequency converter coupled to a counter. The output of the voltage-to-frequency converter which is proportional to the line voltage is accumulated for the period of one cycle of the line frequency. This produces in the counter at the end of each measurement interval, a number of counts proportional to the average line voltage. The microprocessor using the count obtained adjusts the welding current by altering the timing of the firing points of the SCR contactors used to control the welding current.

Abstract: A method to control the welding transformer residual magnetizing current which normally continues circulating in the secondary circuit at the end of each welding pulse until the tips are opened. By utilizing a firing delay of the last half cycle in each welding pulse that brings the algebraic sum of the volt-seconds applied to the transformer to zero at the end of each welding pulse, the residual secondary current is nulled. This alleviates magnetizing current problems which occur in multiple pulse welding.

Abstract: A pre-step timer circuit for pre-advancing the next timer period (control step) in a DC motor controller, such as in a crane-hoist controller. A sensing resistor module is connected from the line side of a contactor coil of a preceding control step to the input of a timer module in series with the accelerating contactor coil in the next control step. This resistor module sensing the previous coil voltage provides a feed-forward path for the sensed voltage signal to pre-time the next timer module. So, if a master switch is left in the previous control step long enough for the next timer module to time out, then the next control step is actuated immediately when the master switch is advanced thereto.

Abstract: A discriminating metal detector that can compensate for ground minerals includes an oscillator circuit having at least two attenuation coils physically located in a probe of the metal detector for ground control. The probe also includes a resonant LC circuit having an inductive coil on the same plane as the attenuation coils but on a different axis than the attenuation coils. The attenuation coils of the oscillator circuit have no magnetic effect on the inductive coil or on the natural response of the inductive coil to metal objects. The attenuation coils of the oscillator operate at a substantially higher frequency than the inductive coil of the resonant LC circuit. As the resonant frequency of the discriminating LC circuit varies due to mineral changes in the ground the oscillator frequency shifts likewise proportionally in order to maintain a constant separation between the two frequencies.

Abstract: An arc chute for a clapper-type electromagnetic D.C. contactor having a closed off top wall with tapered and angled holes therethrough directing jets of air, caused by the arc when the contact tips separate, to the front of the arc chute thereby preventing the arc from moving directly above the contactor and as a result decreasing overhead clearance between contactors and, further improving the upper limit on fault current interruptions.

Abstract: A Power Factor Monitoring and Control System for controlling the quality of a spot weld made in the automotive industry on assembly line welders. The quality and strength of a spot weld can be correlated to a drop in resistance during the fusion process. Rather than measuring this resistive drop at the welding electrodes by attaching external sensing means thereto, the control system of the present invention makes use of the phenomenon that a resistive drop also causes a change in the total load power factor further resulting in a change to the current extinction angle of a weld half cycle. By determining the amount of increase or decrease that has occurred in the current extinction angle during a weld or a group of welds, a basis for the control of the welding heat is obtained.

Abstract: A control system for a multiple speed motor includes a motor circuit having a plurality of resistance varying units in series with the field winding and armature of the motor and separate control circuits for each of the resistance varying units. Each control circuit includes an energizable contactor in series with a gating element and a timer for activating the gating element. The control system includes an activating circuit for bypassing the timer when the level of current flow in the motor circuit is below a certain value. The activating circuit includes a comparator for receiving a reference signal and a signal indicating the level of current flow in the motor circuit and produces an output signal when the current flow is below a certain value which is fed to an OR-gate that also receives a signal from the timer to activate the gating element when either signal is present.

Abstract: A low profile skylight structure having a curb member and a glazing cap joined together in a framework for supporting an insulated glass panel in which the glazing cap is joined to the curb member by concealed fasteners to avoid any visible fasteners or the like.

Abstract: A motor vehicle information system having a programmable automotive tape recorder that can automatically deliver sequential prerecorded messages concerning road information and the like at predetermined intervals. An electromechanical adaptor connected to the odometer system of the vehicle provides pulses that are proportional to the distance traveled and these pulses are fed into a microprocessor which performs arithmetic and logic functions to drive a tape recorder with prerecorded messages. The system permits the distance data for programming the microprocessor and the related sequential messages to be stored directly on the tape such as a prerecorded casesette or for the distance data to be stored in the memory of the microprocessor with the sequential messages on the tape only.