| 主权项 |
1. An ultrasonic cleaning apparatus comprising:
a tank for in use receiving a cleaning liquid and an item to be cleaned; a plurality of transducers arranged, when driven, to direct ultrasonic pressure waves into the tank; and a controller arranged in use to drive the transducers, wherein: first and second transducers from the plurality of transducers are arranged in use to direct ultrasonic pressure waves into an overlapping volume; and the controller is arranged in use to drive the first and second transducers to produce ultrasonic pressure waves at different frequencies from each other wherein the controller is arranged to in use produce first and second drive signals for the transducers, which are each characterised by a centre frequency, a sweep range about the centre frequency and a sweep rate; and to supply the first and second drive signals to the first and second transducers or to groups of first and second transducers from the plurality of transducers respectively, such that the controller comprises a first frequency generator arranged to supply a first drive signal that comprises a primary centre frequency, sweep range and sweep rate, and a secondary centre frequency, sweep range and sweep rate; and a second frequency generator arranged to supply a second drive signal that comprises a primary centre frequency, sweep range and sweep rate, and a secondary centre frequency, sweep range and sweep rate; wherein the controller is arranged in use to control the first and second frequency generators to each switch between primary and secondary operation, with sequential switching taking place to cause different combinations of primary and secondary operation for the first and second frequency generators to occur over time. |
