Abstract: A system for cutting molten plastic material for compression molding includes a rotary-driven cutter mounted in operative association with an extruder which supplies molten plastic. The cutter is driven by a servo motor, the operation of which is coordinated with an associated rotary carousel on which cavities are successively presented to the cutter apparatus. In order to effect separation of each cut discrete quantity of plastic material from the cutting blade of the cutter apparatus, the servo motor is operated to create a period of distinct deceleration during each rotary cutting cycle, thereby effecting separation of the molten plastic from the surface of the cutting blade. The electronic controls of the apparatus further operate to permit the speed at which plastic cutting takes place to be controlled independently of the speed of the associated rotary carousel, while coordinating each cutting cycle with successive presentation of the cavities by the rotary carousel.

Abstract: A velocity control device is disclosed having feedforward signal applied to a velocity servo loop. An actuator moves a laser beam spot to a desired track of an optical disk. A displacement of the laser beam spot outputted from the actuator is differentiated by a differentiator and converted to a signal corresponding to the velocity of the movement of the laser beam spot. A signal corresponding to a distance from the present position of the laser beam spot to the desired track is obtained from the displacement and a desired count value, and is inputted to a function generator to thus obtain a square root of the distance. The difference between the square root of the distance and the moving velocity is obtained by a substracter, and a feedforward signal is added to the difference. The feedforward signal is obtained by differentiating a velocity profile with respect to time with a differentiator.

Abstract: An automated tape library employing a motorized robotic picker wherein the electric motor driving the robotic picker is equipped with two brakes that act simultaneously. The first is a mechanical brake which uses a spring to push a fixed brake pad against the rotating motor. During normal motor operation, an electric solenoid is used to overcome the spring and disengage the brake pad from the motor. When the robotic picker is to be mechanically stopped, the solenoid voltage is turned off and the solenoid releases the spring placing the brake pad in contact with the motor. The second brake is a dynamic electrical brake which makes use of the back emf of the motor to drive a current back into its own windings such that the motor decelerates. The circuit further prevents mechanical brake engagement even at lower motor speeds when back emf is relatively low but robot speed is fast enough to cause mechanical damage if stopped via the mechanical brake.

Abstract: An adjustable frequency motor drive system for a hoist is disclosed in which the frequency of the power supply to the motor can be selectively varied and the speed of the motor will follow the varying frequency at a slip speed relative to the frequency. The slip speed of the motor may not exceed a value beyond which the motor can control the hoist load. Accordingly, a frequency value based on the frequency of the power supply to the motor is selected as the frequency which is not to be exceeded by the motor speed expressed as a frequency. Signals representative of the actual motor speed and the selected frequency value are compared and, if the signal representative of the motor speed exceeds the signal representative of the frequency value which is not to be exceeded, an output signal is produced which may be used to apply a brake which stops and holds the motor and hoist and thereby maintains the load suspended.

Abstract: A reversible d-c motor, driving a load such as a vehicular radio antenna, has its armature winding connected in a transistorized energizing circuit which is activated by a start circuit and locks operated as long as the motor speed surpasses a certain threshold, i.e. until a major obstacle or a terminal position is encountered. The threshold may be determined by a voltage sensor detecting the counter-e.m.f. induced in the armature winding, by a Hall-effect device in the magnetic field of the stator, or by a speed sensor. The armature winding lies in series with a current limiter which determines the maximum torque applied to the load and may also transmit a no-load signal to a protective circuit when the motor is found idling, the protective circuit including a timer which cuts off the motor after a predetermined idling period. Alternatively, the operating period may be determined by a pulse counter de-energizing the motor after a preferably settable number of rotor revolutions.

Abstract: A braking system for transportation apparatus, such as an escalator, having an electrical drive. The braking effort applied when the transportation apparatus is to be stopped is inversely proportional to the electrical energy being consumed by the electrical drive at the time the stopping decision is made.