GB1217692A - Improvements in and relating to drive transmission systems - Google Patents

Abstract

1,217,692. Change speed gearing. HOTPOINT Ltd. 24 April, 1968 [24 April, 1967], No. 18694/67. Heading F2D. In a washing machine drive transmission system speed control means, responsive to centrifugal force, tend to increase the ratio of output shaft speed as the speed of one of the shafts increases and inhibiting means, responsive to the system load, prevent operation of the control means in the ratio increasing sense until the load has fallen below a particular value. The pulley (1), Fig. 1b (not shown), which drives the horizontal inner clothes drum (not shown) of a washing machine, is driven by belt 2 from a grooved flange 3, Fig. 2a, of an intermediate pulley arrangement which includes a variable diameter pulley. The latter is driven via a belt 5 from a centrifugally expanding pulley 6 carried by the shaft 7 of a two-speed electric motor. The flange 15 of the pulley 4 is movable against the force of spring 16 to increase the effective diameter of the pulley unless it is prevented from moving by pivoted weights 21 which move outwardly under centrifugal force against spring loading. The flange 30 of pulley 6 is movable by bob-weights 33 to increase its effect diameter. Operation.-In the condition shown in Figs. 2a, 2b in which pulley 6 is driven at slow speed the centrifugal force due to weights 33 is insufficient to expand the pulley which remains at its smallest effective size and pulley 4 remains at its largest effective size. Increasing the driving motor speed increases the driving torque which is dependent on the load of the drum and is reduced as water is pumped out. Whilst the driving torque is heavy the tension in the drive side of the belt tends to separate flanges 15 and 3 so that flange 15 exerts pressure to the left on flange 17 which traps weights 21 and prevents them from moving outwardly. When the drum load decreases less driving torque is required and belt tension is lessened enabling the release of weights 21. Bob weights 33 are then able to expand the effective diameter of pulley 6 resulting in a corresponding reduction of the effective diameter of pulley 4 and increase in drum speed.