Abstract: A safety device for an electric power tool, especially a portable tool. It has a main switch, electronic controls, a tachometer-generator, and a relay. The relay electrically parallels the motor, acts on the supply of current to the motor through a relay contact, and is activated through the tachometer-generator and through a subsequent safety circuit. To provide a means of switching off the motor at excessively high speeds that will be inexpensive to manufacture and that will maintain a constant switch-off reference speed throughout its life, the safety circuit consists of a synchronization stage, an adjustable timer stage, a processing stage, an ignition amplifier, and an output section.

Abstract: A passenger vehicle door obstruction sensing control apparatus includes a first time period that begins when a door close command signal is received and the vehicle doors start to close. This first time period permits the door drive motor to reach a steady-state speed of operation. Then a motor speed responsive signal is provided to a speed reduction sensing apparatus for opening the doors for a second time period whenever the motor speed reduces below a predetermined limit.

Abstract: An apparatus for use in an automatic door system. Means are provided which compares the current position of the running door with a deceleration point to generate a low speed command upon their coincidence. A speed control responds to decelerate the door to a selected low speed. A measuring device measures a variable run-length of the door which is subject to variations in the mechanical condition of the door. In one embodiment, the device measures a low speed run-length over which the door has moved at a low speed. A comparator compares the measured low speed run-length with a preselected optimal low speed run-length to obtain error or departure from the optimal value. A correction logic produces an updated deceleration point by removing the error from the former deceleration point.

Abstract: A vacuum cleaner control providing solid state high and low speed electronic control of a vacuum cleaner motor. The control circuit is arranged to terminate operation of the motor in the event the sensed speed of a brush driven by the motor drops below a predetermined low speed as by jamming of the brush. A membrane touch switch panel includes switches which provide manually controlled inputs to the control. In one form, the control uses phase control in setting the low speed operation of the motor and in another form, the control utilizes half wave rectification in setting the low speed motor operation.

Abstract: An elevator control apparatus in which a three-phase AC output from a three-phase AC generator rotating with running movement of an elevator car is converted into a train of pulses, and the number of such pulses is counted by a counter which provides a count indicative of the position of the elevator car. When the elevator car is actuated to start from its standstill condition, the running direction of the elevator car is detected on the basis of the direction of phase rotation of the three-phase AC output from the generator, and a predetermined correction data is added to or subtracted from the count depending on the detected running direction of the elevator car so as to correct the count error appearing in the starting stage of the elevator car.

Abstract: In a DC motor control apparatus for driving a DC motor in accordance with a signal of the difference between a revolving speed signal from a speed detector coupled with the DC motor and a command speed signal so as to drive the DC motor at a revolving speed indicated by the command speed signal, when a voltage to be applied to the DC motor and the revolving speed signal from the speed detector are both detected, the operation of the DC motor control apparatus is decided as normal, and when the voltage to the DC motor is detected but the revolving speed signal from the speed detector is not detected, the operation of the DC motor control apparatus is decided as abnormal and an alarm signal is produced.

Abstract: An electronic tachometer utilizes a transducer, typically an optical encoder disc, connected to a movable mechanical element. The transducer produces a pair of triangular waves of fixed relative phase, each having slopes proportional to the velocity of the mechanical element. The triangular waves are differentiated and the resultant signals are sampled by gating pulses derived from the triangular waves themselves. The samples are combined to produce an output signal having a magnitude proportional to element speed and a polarity indicative of direction.In a combined system in which the transducer is attached to the shaft of a brushless motor, another output of the same transducer is used for commutation control of the motor stator windings. This arrangement is particularly useful in a velocity servo system, in which the tachometer output is compared with a signal indicating desired motor velocity. The comparator output is used to modify the commutation control so as to produce the desired motor velocity.

Abstract: Apparatus for detecting the RPM of any rotational material handling assembly such as those used in coal mining or textile manufacturing and including the electrical relay switches to shut down the assembly motors when an underspeed condition is sustained. A proximity switch detects the periodic presence of a metal target attached to the rotating member of the material handling assembly and generates digital pulses responsive to the belt speed. The pulses are supplied to a missing pulse detector which generates an output if the time it takes the rotating member to complete one revolution is longer than a preset adjustable reference time. The output, which indicates an underspeed condition, is used to de-energize a relay which is interlocked to the rotational material handling assembly drive motor thus shutting the motor down.

Abstract: Apparatus for detecting excessive slippage of a conveyor belt, as used, for example, in the coal mining industry includes electronic switching devices. A ring having a plurality of magnets thereon is mounted on a belt roller, and a detecting coil produces voltage pulses in response to the passage of the magnets. The voltage pulses are amplified, squared, and replaced by fixed width pulses at a frequency proportional to belt speed. The fixed width pulses are integrated to provide an average voltage having a value proportional to the conveyor belt speed. The average voltage is compared with an adjustable reference, and is used to turn off the belt driving motor when belt speed drops below a predetermined threshold.