Abstract: A motor speed control system comprises an encoder (12) which produces a series of indicator pulses related to the motor's speed. The period of the pulse is compared with that of a crystal-controlled reference period produced by a period generator (14). Comparison is made by means of a period comparator (16) consisting of logic elements, including flip-flops (F1, F2, F3) and gates (G1 and G2). Digital outputs of the period comparator control UP and DOWN charge pumps whose integrated value controls the motor through a power driver. Advantages of the system are precise digital control with crystal accuracy.

Abstract: A bearing unloading mechanism for a disc clamping unit utilized in rigid disc certifiers or testers comprises a hollow spindle (12) containing a pulling rod (20) which slides in the spindle. The upper end of the pulling rod carries a clamping element (26) for clamping a disc (D) to be tested or certified. There is a first compression spring (32) arranged between a flange (30) at the lower end of rod (20) and second compression springs (56) between stationary casing (18) and a moveable casing (48) which is attached to a pneumatic cylinder (40), solenoid, or any other linear actuator. When the actuator is energized, the moveable casing moves down, compressing the second springs until the moveable casing comes into contact with an abutment flange (58) of the spindle. At this point the device continues to move the rod connected to the clamp up to the unclamped position.

Abstract: A motor speed control circuit produces indexing pulses during each revolution of the motor. Each indexing pulse triggers the production of a predetermined pattern of timing pulses. The timing pulses are integrated. The result of the integration is a relatively constant level signal that controls the motor current. At the end of a predetermined pattern of pulses in the binary signal, the integrator input signal goes to one of two binary states and causes the integrator output voltage to ramp up or down, as the case may be, until another indexing pulse is received from the motor. The output of the integrator upon receipt of the indexing pulse controls the speed of the motor while another set of binary pulses are being integrated.