Controller for a high frequency agitation source

• US 7,825,564 B2
• Filed: 02/07/2007
• Issued: 11/02/2010
• Est. Priority Date: 02/08/2006
• Status: Expired due to Fees

• Current Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Original Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Inventors: Douglas, Paul Graham, Croft, Nathan James
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US12/162,300
• Publication Number:
  US 20090026883A1
• Time in Patent Office: 1,364 Days
• Field of Search: 310/316.01, 310/316.02, 310/316.03, 310/317, 310/319, 310/3
• US Class Current: 310/317
• CPC Class Codes: B06B 1/0261 taken from a transducer or electrode connected to the driving transducer

Abstract

A controller for a high-frequency agitation source includes a signal generator to generate a drive signal having a variable duty cycle. The drive signal is used to drive the high-frequency agitation source. The controller also includes a temperature detector to detect the temperature of the high-frequency agitation source. The controller is configured to vary the duty cycle of the drive signal in response to the temperature of the high-frequency agitation source. By varying the duty cycle of the drive signal, the average power supplied to the piezoelectric crystal can be varied while still maintaining a fixed amplitude of oscillation. This allows the temperature of a high-frequency agitator, for example, a piezoelectric crystal, to be controlled.

Claims

1. A hand dryer, comprising:

a cavity having an opening at an upper end, the opening being sized to allow a user'"'"'s hands to be inserted into the cavity;

a plurality of slot-like openings positioned at the upper end of the cavity;

a motor unit, having a fan to generate high speed airflow, the fan being functionally connected to the plurality of slot-like openings to direct the high speed airflow through the slot-like openings;

a drain, located at a bottom end of the cavity, to receive water removed from the user'"'"'s hands;

a collector, located downstream of the drain, to collect the water removed from the user'"'"'s hands; and

a nebulizer, located in the collector, the nebulizer, comprising,

a high-frequency agitation source,

a controller for the high-frequency agitation source,

a signal generator to generate a drive signal having a variable duty cycle and being used to drive the high-frequency agitation source, and

a temperature detector to detect a temperature of the high-frequency agitation source,

wherein the controller is configured to vary the duty cycle of the drive signal in response to the temperature of the high-frequency agitation source.

2. A hand dryer as claimed in claim 1, wherein the controller varies the duty cycle in order to prevent the temperature of the high-frequency agitator exceeding a pre-determined operating temperature.

3. A hand dryer as claimed in claim 1 or 2, wherein the duty cycle is set to a maximum value by the controller at the start of an operation of the high-frequency agitation source.

4. A hand dryer as claimed in claim 1 or 2, wherein the controller is further configured to control the drive signal in response to a first pre-determined requirement and to determine when the first pre-determined requirement has been satisfied.

5. A hand dryer as claimed in claim 4, wherein the first pre-determined requirement is that the duty cycle is reduced below a pre-determined value.

6. A hand dryer as claimed in claim 4, wherein the first pre-determined requirement is the detection that a pre-determined time period has elapsed.

7. A hand dryer as claimed in claim 4, wherein the first pre-determined requirement is the detection of a pre-determined temperature condition.

8. A hand dryer as claimed in claim 4, wherein the controller is configured to cause the drive signal to switch off when the first pre-determined requirement is satisfied.

9. A hand dryer as claimed in claim 1 or 2, wherein the controller is arranged to cause the drive signal to switch off in the event that no change of temperature is observed when the high-frequency agitator is operated.

10. A hand dryer as claimed in claim 1 or 2, wherein the controller is arranged to cause the drive signal to switch off when the temperature exceeds a pre-determined maximum value.

11. A hand dryer as claimed in claim 1 or 2, wherein the controller determines a maximum operation time for which the drive signal shall remain on and causes the drive signal to switch off when the maximum operation time is exceeded.

12. A hand dryer as claimed in claim 1 or 2, wherein the controller detects the temperature of the high-frequency agitator at pre-determined intervals.

13. A hand dryer as claimed in claim 1, comprising a further temperature detector to detect the temperature of at least a part of the signal generator, the controller being configured to vary the maximum duty cycle of the drive signal in response to the temperature of the at least a part of the signal generator.