GB1211330A - Method of speed regulation for centrifuges, particularly in washing machines - Google Patents

Abstract

1,211,330. Automatic control of speed. HOLZER PATENT A.G. Oct.23, 1967 [Oct.24, 1966; April 12, 1967], No.34816/70. Divided out of 1,209,177. Heading G3R. [Also in Division F4] The speed of a centrifuge motor 11, e.g. in a washing machine is controlled by supplying it with repeated bursts of A.C. (e.g. via a triac) which are influenced by a comparison between the output of a tachogenerator 12 and a reference signal, and a final speed n 2 is reached after at least one intermediate stage n 1 . The motor control is by an undisclosed, known device 13. As shown, the motor is accelerated at full power to n i , and then at full power again to n 2 after an interval determined by a timer 14. In a second embodiment Fig.2 (not shown) the separate timer is replaced by an RC circuit in the controller. In Fig.3 (not shown), acceleration to the final speed is initiated when the on/off ratio of the bursts of A.C. falls to a predetermined value (showing), that the load has also fallen). In Fig.4 (not shown), the reference value for the speed is gradually increased (by an RC circuit) to the value n 1 , whereupon it immediately increases to the value n 2 , producing maximum acceleration from n 1 to n 2 only. In Fig.5 (not shown), the arrangement of Figs. (3 and 4) are combined, the motor being gradually accelerated to the speed n 1 where it remains until the on/off ratio has dropped, causing maximum acceleration to n 2 . Transistor circuits for the on/off ratio detecting device and for varying the reference value are described Figs.6 and 7 (not shown). Also described are an arrangement for maintaining the speed at n 1 until a water level switch indicates sufficient water has drained away, and for switching it off or reducing its speed for a predetermined time if vibration or bearing forces are excessive. The speed n 1 is chosen to be below the critical speed range.