CONTROL MEANS FOR AIR EMITTING APPARATUS

Abstract: A control circuit (24) is provided for controlling a hand dryer or similar apparatus. The control circuit (24) includes timers which operate the fan of the dryer from time to time, without activating its heating element (20), so that a stream of air is passed over a fragrant or disinfectant element from time to time when the device is not in use. A light sensor disables the circuit at night.

Description: CONTROL MEANS FOR AIR EMITTING APPARATUS BACKGROUND OF THE INVENTION This invention relates to control means for controlling the operation of apparatus which has an electrically powered impeller arranged to emit a stream of air. Electrically powered hand dryers are Icnown, for example from South African Patent no. 96/10586 of the present applicant, in which a carrier is mounted in an air flow path of the apparatus so that operation of the apparatus introduces a fragrance, disinfectant or deodorising agent into the air stream emitted by the apparatus. It is an object of the invention to provide a control means which can be used with such apparatus and similar apparatus, such as hairdryers. SUMMARY OF THE INVENTION According to the present invention there is provided a control circuit for controlling the operation of apparatus having an electrically powered impeller arranged to emit a stream of air, the control circuit comprising: at least a first timer arranged to determine a first time interval; a controller responsive to the first timer to generate control signals at intervals corresponding to the first time interval; and switch means responsive to the control signals and arranged to connect the impeller to an electrical source selectively, to operate the impeller periodically. The control circuit may be adapted to control an electrically powered hand dryer or hair dryer. Preferably, the control circuit includes a carrier for a fragrance and/or disinfectant and/or deodorant which is located in an air flow path of the apparatus, so that operation of the apparatus causes a stream of fragrant and/or disinfecting and/or deodorising air to be emitted. The controller may include a second timer arranged to determine a second time interval, the controller being responsive to the second time interval to generate control signals to which the switch means is responsive to operate the impeller for periods corresponding to the second time interval. The first and second timers are preferably implemented using an integrated circuit timer with associated passive components which determine the first and second time intervals. The first time interval is preferably at least ten times longer than the second time interval. The controller may also include a light sensor arranged to disable the controller selectively when the ambient light falls below a predetermined ambient light level. The control circuit preferably includes a reset circuit arranged to restart a timing cycle of the first timer after the apparatus has been used. According to the present invention there is further provided apparatus having a housing defining an air flow path comprising an inlet and an outlet, a carrier for a fragrance and/or disinfectant and/or deodorant located in the air flow path, and an impeller arranged to be driven by an electric motor to emit a stream of air from the outlet, the apparatus further including a control circuit comprising: at least a first timer arranged to determine a first time interval; a controller responsive to the first timer to generate control signals at intervals corresponding to the first time interval; and switch means responsive to the control signals and arranged to connect the motor to an electrical source selectively, to operate the impeller periodically and thereby to cause a stream of fragrant and/or disinfecting and/or deodorising air to be emitted. The apparatus may be a hand dryer or hair dryer which includes a heating element in the air flow path, the control circuit being arranged to bypass the heating element when operating the impeller. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a pictorial view of an electrically powered hand dryer fitted with a control circuit according to the invention; Figure 2 a rear view of the hand dryer with its back panel opened; Figure 3 is a sectional side view of the apparatus, showing the location of a circuit board of the control circuit; and Figure 4 is a schematic circuit diagram of the electronic circuitry of the control circuit. DESCRIPTION OF AN EMBODIMENT The basic hand dryer apparatus illustrated in Figures 1 to 3 is substantially similar to the apparatus described in the complete specification of South African Patent No. 96/10586 of the present applicant, the contents of which are incorporated herein by reference. Briefly, the apparatus comprises a cover 10 moulded from a tough, heat resistant plastics material which is hinged to a back plate 12 which can be fixed to a wall 14 or other support surface. The cover 10 has a cool air inlet 14 on its lower surface and a hot air outlet 16, with an air flow path extending between the inlet and the outlet. As described in Patent no. 96/10586, a carrier (not shown) is mounted in the air flow path of the apparatus so that operation of the apparatus introduces a fragrance, disinfectant and/or deodorising agent into the air stream emitted by the apparatus. A fan or impeller assembly comprising an impeller disposed within a cowl and arranged to be driven by an electric motor is attached to the inner surface of the cover adjacent to the outlet 16, so that operation of the motor causes air to be drawn into the inlet 14 and expelled via the outlet 16. A heating element 20 is located inwardly of the outlet 16 and is normally activated when the hand dryer is operated, to heat the stream of air emitted by the apparatus. Typically, a proximity sensor (not shown) is located adjacent to the outlet 16 and detects the presence of the hands of a user of the apparatus. Signals from the sensor are fed to a control circuit 22 which operates the motor and the heating element to a cause a stream of hot air to be emitted from the apparatus. The apparatus of the invention further includes a control circuit 24 which is conveniently built on a circuit board which is encapsulated and mounted on one of the side walls of the cover as shown in Figures 1 to 3. The control circuit includes first and second timers which are arranged to set respective first and second time intervals, so that the control circuit causes the motor of the apparatus to operate periodically at intervals determined by the first time interval, for a period determined by the second time interval. This is achieved by fitting a relay or other suitable switch means which controls the electrical supply to the motor independently of the conventional control circuit 22. In addition, a light sensor is provided which detects the ambient light in the vicinity of the apparatus. When the ambient light level falls below a predetermined threshold, the control circuit is disabled, so that the apparatus does not run at night, for example. The schematic circuit diagram of the control circuit is shown in Figure 4. The control circuit includes a power supply comprising a mains dropping resistor Rl and a capacitor Cl with an associated bleeder resistor R9. A diode bridge comprising diodes Dl to D4 provides a raw DC output of approximately 24 volts DC for operating the coil of a relay, with additional zener diodes Zl and Z2 and a smoothing capacitor C6 arranged to provide a smoothed 15 volt DC output for the control circuitry itself. The control circuit is based around a type (555) integrated circuit timer IC2 with an associated timer capacitor C2, a first resistor network comprising resistors R5. R6, R7, R8 and Rl 1, and a second resistor network comprising resistors R16, R14, R13 and R12, which determine the respective first and second time intervals. In operation, after the first interval has elapsed, the output of the timer circuit goes low for a period equal to the second time interval, with this process being repeated indefinitely while the circuit is operational. The respective timing intervals are determined by the charge/discharge time constants of the timing capacitor C2 and the respective resistor networks, and can be varied by changing jumper settings on the circuit board. It will be appreciated by one skilled in the art that any other type of electrical timer may be used in place of the abovementioned timer circuit. Alternatively, a mechanical timer may be used which could take the form of, for example, a mechanical clock of the type used in common time switches. The control circuit could then be adapted accordingly. The circuit includes a light sensor PL1 which is connected to pin 3 of the timer IC, which outputs a reference voltage which is set by resistors R3 and R4. With sufficient ambient light intensity, the sensor conducts sufficiently to pull the inverting input of a comparator comprising an op amp IC 1A low. If the output of the timer circuit IC2 and the voltage at the inverting input of the op amp IC1A are both low, then the op amp output will be high, turning on a relay-switching transistor TR2 and energising the coil of a relay REL1. This supplies mains current to the fan motor. However, the heating element 20 is not energised in this mode of operation. In the absence of sufficient ambient light, the voltage at the inverting input of the op amp comparator is high, so that the relay will not be operated irrespective of the state of the timer output. When the transistor TR2 is off, the normally closed contact of the relay REL1 connects the terminal M+ to the motor, allowing normal operation of the hand dryer. The control circuit includes a reset circuit which resets the timer integrated circuit so that it restarts its timing cycle after the last time the hand dryer has been used. It will be appreciated that the above described control circuit does not interfere with normal operation of the hand dryer, but causes the motor of the hand dryer to run from time to time, typically at intervals of 10, 15, 20 or 25 minutes for a period of, say, 10, 20, 30 or 40 seconds. In other words, the first time interval is substantially longer than the second time interval, by a factor of at least 10 and preferably about 50 or 60 (eg. a ratio of, say, 10 minutes to 10 seconds). This results in a fragrance, disinfectant or deodorant being introduced into the air in the vicinity of the hand dryer from time to time, enhancing the nearby environment. The heating element is not required in this mode of operation and is therefore bypassed. The above circuit, although illustrated as a discrete unit, can be incorporated into a larger circuit which controls the other functions of the apparatus with which the control circuit is to be used. It will be appreciated that the application of the invention is not limited to hand dryers as such, but could be applied to hair dryers such as those commonly provided in hotel bathrooms, or other apparatus arranged to emit a stream of air.

Claims: CLAIMS: 1. A control circuit for controlling the operation of apparatus having an electrically powered impeller arranged to emit a stream of air. the control circuit comprising: at least a first timer an-anged to determine a first time interval; a controller responsive to the first timer to generate control signals at intervals corresponding to the first time interval; and switch means responsive to the control signals and arranged to connect the impeller to an electrical source selectively, to operate the impeller periodically. 2. A control circuit according to claim 1 wherein the control circuit is adapted to control an electrically powered hand dryer or hair dryer. 3. A control circuit according to claim 2 wherein the control circuit includes a carrier for a fragrance and/or disinfectant and/or deodorant which is located in an air flow path of the apparatus, so that operation of the apparatus causes a stream of fragrant and/or disinfecting and/or deodorising air to be emitted. 4. A control circuit according to any one of claims 1 to 3 wherein the controller includes a second timer arranged to determine a second time interval, the controller being responsive to the second time interval to generate control signals to which the switch means is responsive to operate the impeller for periods corresponding to the second time interval. 5. A control circuit according to claim 4 wherein the first and second timers are implemented using an integrated circuit timer with associated passive components which determine the first and second time intervals. 6. A control circuit according to claim 4 or claim 5 wherein the first time interval is at least ten times longer than the second time interval. 7. A control circuit according to any one of claims 1 to 6 wherein the controller includes a light sensor arranged to disable the controller selectively when the ambient light falls below a predetermined ambient light level. 8. A control circuit according to any one of claims 1 to 7 including a reset circuit arranged to restart a timing cycle of the first timer after the apparatus has been used. 9. Apparatus having a housing defining an air flow path comprising an inlet and an outlet, a carrier for a fragrance and/or disinfectant and/or deodorant located in the air flow path, and an impeller arranged to be driven by an electric motor to emit a stream of air from the outlet, the apparatus further including a control circuit comprising: at least a first timer arranged to determine a first time interval; a controller responsive to the first timer to generate control signals at intervals corresponding to the first time interval; and switch means responsive to the control signals and arranged to connect the motor to an electrical source selectively, to operate the impeller periodically and thereby to cause a stream of fragrant and/or disinfecting and/or deodorising air to be emitted. 10. Apparatus according to claim 9 which is a hand dryer or hair dryer which includes a heating element in the air flow path, the control circuit being arranged to bypass the heating element when operating the impeller.

Inventors: JACKSON SIMON ALEXANDER, SCHEEPERS ROGER BASIL LAWSON, JACKSON, SIMON, ALEXANDER, SCHEEPERS, ROGER, BASIL, LAWSON
Applicants: CASTLEGATE TRADING LTD, JACKSON SIMON ALEXANDER, SCHEEPERS ROGER BASIL LAWSON, CASTLEGATE TRADING LIMITED, JACKSON, SIMON, ALEXANDER, SCHEEPERS, ROGER, BASIL, LAWSON
Application year: 1999
Main classification: A47K10
IPC codes: A45D20, A47K10