Abstract: There is provided a safety switch having a housing configured to receive a removable key, and a mechanism arranged to be operated when the key is moved from an engaged position to a partially disengaged position, the mechanism being arranged to cause a signal to pass to a separate apparatus, wherein the safety switch further comprises a lock which is controlled by the separate apparatus and is arranged to prevent the key from being fully disengaged from the safety switch until a signal has been received in response from the separate apparatus.

Abstract: The present invention relates to combination control systems employing at least one intermediate module between different control modules and, in one embodiment, relates to a system for isolating a load from multiple power sources. The system includes a first power isolation system capable of receiving a first power from a first input port and determining whether the first power is communicated to a first output port, and a second power isolation system capable of receiving a second power from a second input port and determining whether the second power is communicated to a second output port. The system further includes an intermediate module connected with the first and second power isolation systems, where the intermediate module allows for at least one intermediate control signal to be provided to both of the power isolation systems.

Abstract: The present invention relates to an intermediate module capable of being implemented in conjunction with a safety isolation system, as well as a control system employing such an intermediate module and related operational method. In one embodiment, the intermediate module includes a first input terminal capable of receiving a first signal from an additional device that is at least one of the safety isolation system and another device, and a first output terminal capable of providing a second signal to a controlled device. The intermediate module additionally includes at least one safety relay circuit that receives at least one of the first signal and a first intermediate signal based upon the first signal, and that generates in response at least one of the second signal and a second intermediate signal upon which the second signal is based. The safety relay circuit includes at least one redundant circuit component.

Abstract: The present invention relates to combination control systems employing at least one intermediate module between different control modules and, in one embodiment, relates to a system for isolating a load from multiple power sources. The system includes a first power isolation system capable of receiving a first power from a first input port and determining whether the first power is communicated to a first output port, and a second power isolation system capable of receiving a second power from a second input port and determining whether the second power is communicated to a second output port. The system further includes an intermediate module connected with the first and second power isolation systems, where the intermediate module allows for at least one intermediate control signal to be provided to both of the power isolation systems.

Abstract: There is provided a safety switch having a housing configured to receive a removable key, and a mechanism arranged to be operated when the key is moved from an engaged position to a partially disengaged position, the mechanism being arranged to cause a signal to pass to a separate apparatus, wherein the safety switch further comprises a lock which is controlled by the separate apparatus and is arranged to prevent the key from being fully disengaged from the safety switch until a signal has been received in response from the separate apparatus.

Abstract: A switching filter is disclosed for discriminating false control signals from actual control signals. The switching filter is particularly useful on a high impedance input, such as that of a motor controller. The filter is designed to compensate for capacitive, inductive, and/or resistive coupling between extended control lines that are run in parallel with other power lines. A low impedance is switched into the otherwise high impedance control line input for a brief instant to dissipate and phase shift false control signals to prevent the controller from interpreting the false signals as actual control signals. The filter includes a first resistor connectable to sense a presence of a possible false control signal, and a second resistor, having much lower resistance than the first resistor, connected in a path between the control line input and circuit common.

Abstract: A contactor has an armature, a pull-in coil and a holding coil. When the system is energized through a first switch such as a thermostat, the low current holding coil is energized in preparation for holding the armature pulled in after the pull-in coil is energized and the armature has finished its power stroke. A solid-state switching device and the pull-in coil are connected in series between both terminals of a power source. A control circuit causes the solid-state switching device to be conductive the instant power is supplied to the circuit through the first switch. One embodiment of the control circuit is based on logic gates. RC circuits associated with the gates keep the solid-state switching device and pull-in coil conducting long enough for the armature to pull-in. After the solid-state switching device turns on, the transistor is controlled to turn off, deenergizing the pull-in coil while the holding coil holds the armature in until the first switch opens and power input is discontinued.

Abstract: An overload control circuit and method of operation for protecting a three-phase motor from damage due to overload includes monitors reading the load on each phase of the motor and circuitry for combining the three separate phase signals into a single combined load signal which triggers the overload circuit. The gain on the combined load signal and the overload trip delay time may be calibrated and monitored by an external meter to provide for accurate and inexpensive calibration to accommodate specific operating characteristics of the motor being monitored. The circuit provides visual readouts of the mode of operation, including: (1) operating mode; (2) overload onset; (3) shut down initiated; and (4) delay to restart.