Cyclical centrifugal machine

In a cyclical centrifugal machine including a solids retaining centrifugal basket and a rotary electric motor for bringing the basket to and driving it at any of several different speed conditions, a system for controlling transmission of torque from the motor to the basket comprising:

• clutch means including relatively rotatable confronting clutch members adapted to transmit torque through liquid films between them, one set of said members being rotatable with said motor and a second set of said members being rotatable with said basket, means for circulating a liquid to and between said clutch members for torque transmission and from said members for dissipation of heat from the liquid, and means for displacing at least one set of said clutch members relative to said second set to vary the torque transmitted through said films;
• load signal generating means for generating a control current proportional to the current drawn by and thus the load on said motor during its operation;
• means for generating a control voltage constituting a load signal from said current;
• speed signal generating means comprising a radially toothed gear mounted for rotation with said basket and a magnetic pick-up mounted adjacent and responsive to rotation of the teeth of said gear for generating a pulsating voltage constituting a speed signal having a frequency proportionate to the speed of said basket;
• means for generating a load reference signal representing a maximum load to be placed on said motor for producing a desired speed;
• means for generating a speed reference signal including selectively settable means for generating a said speed reference signal corresponding to each of said speed conditions, and means for varying the setting of said settable means at appropriate intervals in each operating cycle of the machine;
• means including a first signal amplifier for comparing said load signal and said load reference signal and generating a load error signal corresponding in magnitude to any difference between the same;
• means including a resistor for receiving said speed signal and said speed reference signal and producing a speed error signal corresponding in magnitude to any difference between them;
• means for combining said load error signal and said speed error signal and thus producing a resultant signal representing at any given moment the relationship of the actual load on said motor to said maximum load;
• control means responsive to said resultant signal for operating said displacing means and, thus, varying said torque so as to produce said maximum load on the motor.

A method for controlling transmission of torque from the electric motor in a cyclical centrifugal machine to the solids retaining basket thereof with clutch means including relatively rotatable confronting clutch members adapted to transmit torque through liquid films between them, said motor having low and high speed windings for bringing said basket to different lower and high rotational speeds, said method comprising the steps of:

• circulating liquid to said clutch means to form liquid films between said confronting clutch members;
• energizing said motor on said low speed winding to bring it to its low synchronous speed;
• operating said clutch members to increase the torque transmitted through the liquid films between them from said motor to said basket;
• when the speed of the basket approaches said low synchronous motor speed, operating said clutch members to discontinue transmission of torque through said liquid films;
• energizing said motor on said high speed winding to bring it to its high synchronous speed;
• operating said clutch members to increase the torque transmitted from said motor to said basket until the speed of said basket approaches said high synchronous motor speed;
• and
• circulating said liquid from said clutch means for dissipation of heat from said liquid.