GB2084012A - Automatic hand dryer - Google Patents

Abstract

A warm-air drying apparatus for drying hands includes a sensor (20) for sensing the presence of an object, e.g. a user's hand, in proximity to the apparatus and within a predetermined region that is spaced from the apparatus and adjacent a warm-air outlet (13), and which energises a blower (11) and heating element (12) of the apparatus only in response to the presence of an object in that region being sensed thereby. The sensor may include means for transmitting an ultrasonic pulse signal, means for receiving the reflection from a proximate object, and discriminator means which defines a predetermined time period following transmission of the pulse and which generates an output signal for controlling energisation of the blowing and heating means in response to the reflected signal being received during said predetermined time period. <IMAGE>

Description

SPECIFICATION Warm-air drying apparatus This invention relates to warm-air drying apparatus, and in particular to warm-air drying apparatus for drying hands or other parts ofthe body.

Warm-air drying apparatus for drying hands generally includes an electrically-operated blower and a heating element which are arranged to produce a flow of heated air and an outlet which directs the flow of air overthe user's hands. Means are also provided to energise the blower and heating ele ment when it is desired to use the apparatus.

Heretofore, it has been common to provide a manually-operable switch which the user operates to control energisation of the blower and heating element. However, manually-operable switches are generally undesirable as physical contact is necessary for their operation and a health hazard is thus involved. Furthermore, such manually-operable switches may inadvertently be left in their'on' condition when the user has finished with the apparatus, thereby wasting energy. In order to overcome this problem, it has also been common to provide an associated timing arrangement whereby manual operation of the switch results in the blower and heating element being energised for a predeter mined period of time only.However, if the user requires a longer than normal time in which to dry his hands, it then becomes necessary for the user to actuate manually the switch again once the predetermined period of time allowed by the timing arrangement has expired which is both inconvenient to the user and increases the health hazard. Such operation is therefore considered unsatisfactory.

It has also been proposed to effect energisation of warm-air hand dryers by providing means for sensing the proximity of an object, for example the hands, and energising the blower and heating element in response to proximity being detected. Such means may take the form of a capacitive plate sensor within the apparatus. However, these sensors are again unsatisfactory in that an obiect left inadvertently, or indeed intentionally, against the apparatus may cause continual energisation of the blower and heating element with a subsequent wastage of energy. The provision of a timing arrangement as previously mentioned would not be effective to overcome this problem.

It is an object of the present invention to provide a warm-air drying apparatus which substantially overcomes the above disadvantages.

According to one aspect of the present invention, there is provided warm-air drying apparatus for drying hands comprising electrically-operable blowing and heating means which is energisableto produce a flow of warm-air, and means for sensing the presence of an object in proximity to the apparatus and within a predetermined region spaced from the apparatus and adjacent an outlet for said warm air, which is arranged to energise the blowing and heating means only in response to the presence of an object in said region being sensed thereby.

The object whose presence is sensed may be the body or hands of the user of the apparatus.

Preferably, the blower and heating means, which may comprise an electric-motor driven blower and an electrical resistance heating element respectively, are contained in a housing of the apparatus. In this case, the sensing means may also be contained in the housing.

The sensing means may include means for transmitting a pulse signal, means for receiving a reflection of said pulse signal from a proximal object, and discriminator means which defines a predetermined time period following transmission of a said pulse signal and which is arranged to generate an output signal for controlling energisation of the heater and blower means in response to a said reflected pulse signal being received during said predetermined time period indicative of the presence of said object within said region.

Preferably, the discriminator means is arranged such that the said predetermined period of time commences a finite time after transmission of a said pulse signal by said transmitting means and terminates a set time thereafter.

The transmitting means may be arranged to generate a series of pulse signals, in which case the predetermined period of time is defined during the interval between transmission of each successive pair of pulse signals.

The pulse signal preferably is an ultrasonic signal.

The warm-air drying apparatus may also include a timing arrangement which is arranged to energise the blowing and heating means for a predetermined duration in response to presence of an object in the proximity of the apparatus being sensed by the said sensing means.

Warm-air drying apparatus in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawing in which: Figure 1 is a schematic cross-sectional view through a warm-air drying apparatus; and Figure 2 is a block diagram of a sensing arrangement of the drying apparatus.

Referring to Figure 1, the warm-air hand drying apparatus general!y comprises a housing 10 of metal or plastics which contains an electric-motor driven centrifugal blower 11 that is operable to draw air into the housing 10 through an inlet (not shown) and force the air over an electrical resistance heating element 12 and thence through an outlet nozzle 13 in the housing 10 onto a user's hands such that the flow of warm-air issuing from the nozzle 13 serves to dry the user's hands. The apparatus can also be used to dry a user's face or other parts of the body. In this respect, the nozzle 13 may be moveable with respect to the housing 10 so that the flow of warm-air can be directed accordingly.

Electrical power is fed through a lead 15 to a circuit 16 in the housing 10 which controls energisation of the blower 11 and the heating element 12 through leads 17 and 18 respectively.

The warm-air drying apparatus includes a sensor which is arranged to provide an output signal to the control circuit 16 to effect operation of the control circuit 16, and thereby energise the blower 11 and heating element 12, only in response to the presence of an object, for example a user's hand, head or body, being detected in a survey region adjacent to and spaced from the outlet nozzle 13 of the apparatus.

The sensor comprises an ultrasonic sensor unit 20 disposed within the housing 10 which is connected to the control circuit 16 through a lead 21 and arranged to emit an ultrasonic signal, as shown schematically by the dotted line 22, from a transmit terofthe sensor 20 towards a survey region adjacent the outlet nozzle 13. In practice, the signal is transmitted as a diverging beam so as to cover a wider area.

Sould an object, for example a user's hand, generally indicated at 23, be present.within that region, part of the signal 22 is reflected back by the hand 23 along the path shown schematically by the dotted line 24 to a receiver in the sensor unit 20. A processing circuit within the sensor 20 is arranged to detect whether the reflected signal 24 is indicative of the fact that the hand is located in particular region adjacent to, but spaced a set distance from the outlet nozzle 13 and to provide an output signal to the control unit 16 accordingly.

Upon receipt of such an output signal from the sensor unit 20, the control circuit 16 energises the blower 11 and heating element 12 whereby a flow of warm-air is produced and directed over the hand by the outlet nozzle 13, as indicated by the arrow 25.

The control circuit 16 includes a time delay circuit which operates to maintain the blower 11 and heating element 12 energised for a pre-set duration following receipt of the output signal from the sensor unit 20 so as to avoid rapid switching on and off of the apparatus. If at the end of the pre-set duration by the time-delay circuit the sensor unit 20 again detects the presence of a user's hand or body within the particular region proximal to the output nozzle 13, the control circuit 16 operates to energise con tinuouslythe blower 11 and heating element 12 for a further duration. Such operation of the apparatus will continue until the user's hand or body is removed from the survey region.

The aforementioned particular survey region is chosen to correspond substantially with the optimal position for drying the body part. As therefore, for example, the hands of the user of the apparatus will normally be positioned in that survey region it can be seen that satisfactory sensing of their presence and operation of the apparatus is ensured. If however any object is either inadvertently or intentionally placed against or immediately adjacent the housing 10 of the apparatus but outside the survey region to which the sensor unit 20 is responsive, the unit 20 will fail to operate the control circuit 16. Similarly the presence of any object further away from the apparatus than the survey region will also have no effect.In this way, spurious operation ofthe apparatus as a result of articles being left nearby is to a certain extent prevented and unnecessary wastage of power avoided.

The sensor unit 20 may be a low-power ultrasonic sensing arrangement as shown in Figure 2.

With reference to Figure 2, the sensing arrangement includes an oscillator circuit 30 which generates an output signal of for example 40 KHz, which is fed to an ultrasonic transmitting transducer 31 and which is controlled by a timing circuit 32 such that the transducer 31 produces a train of discrete ultrasonic energy pulses of, say, 2 milliseconds duration at 8 milliseconds intervals, that are directed by the transducer generally towards the survey region.

If an object, referenced at 23, is present in the path of this ultrasonic pulse signal, the pulses are reflected by the object back towards the sensor unit 20 where they are received by the transducer 33 and converted into electrical form. The electrical signal from the receiving transducer 33, comprising pulses of duration and interval corresponding to the output pulse signal from the oscillator circuit 30 but displaced in time therefrom, are amplified by an amplifier 34 and fed to a discriminator circuit 35.In view of the finite time taken for each ultrasonic pulse to travel from the transducers 31 to the object 23 and return to the transducer 33, the pulse train received by the transducer 33 and supplied to the discriminator circuit 35 is out of synchronism with the output pulse signal from the oscillator circuit 30 (determined by operation of the timing circuit 32) by an amount which is dependent upon the time delay between transmission and reception of the ultrasonic pulses by the transducers 31 and 33 respectively, and therefore indicative ofthe distance of the object 23 from the sensor unit 20.

The discriminator circuit 35 is also connected to the timing circuit 32 and is arranged to operate in response to timing signals obtained from the circuit 32 to define a time slot or 'window' during the interval between successive pulses transmitted by the transducer 31 for sampling the output from the amplifier 34 to the discriminator circuit 35. If a pulse from the amplifier 34 is received by the discriminator circuit 35 during this time slot, a control signal is generated by the discriminator circuit 35 and fed along the lead 21 to the control circuit 16 to effect energisation of the blower 11 and heating element 12. If, on the other hand, a pulse is not received from the amplifier 34 during this time slot, no control signal is generated by the discriminator circuit 35 and the blower 11 and heating element 12 remain unenergised. Thus the sensor unit 20 operates to select and respond to onlythose pulses reflected by the object 23 which are received within a predetermined period of time, as determined by the sampling window, aftertheirtransmission by the transducer 31. As the delay between a transmitted and received pulse varies in accordance with and is directly dependent on the distance of the reflecting object 23 from the sensor unit 20, it will be appreciated that the reception of a pulse during the time slot defined within the discriminator circuit 35 indicates that the reflecting object is within a particular distance range from the sensor unit 20.

By varying the duration- and occurrence of the time slot during the interval between successive transmitted pulses, it is possible to define a particular survey region between an inner range limit spaced from the sensor unit by a finite distance and an outer range limit at a set distance further away from the sensor unit 20. The presence of an object between these two limits causes the discriminator circuit 35 to supply a control signal to the control unit 16. The presence of an object either closer to the sensor unit 20 than the inner limit of the defined survey region orfurther away than the outer limit is ignored by the sensor unit 20 since the reflected pulses do not fall within thepre-arranged sampling period defined by the time slot, and, accordingly, no control signal is generated by the discriminator circuit 35.

As a typical example, the inner limit of the survey region may be chosen to be approximately six inches from the sensing arrangement and the outer limit approximately twelve inches.

The natural attenuation of the low power ultrasonic signals and the consequent reduction in amplitude of reflected pulses renders the sensor unit immune to operation through any reflected pulses from distant objects.

It is envisaged that since the receiving transducer 33 is only required to receive reflected pulses during the non-transmitting mode of the transmitting transducer 31, the same transducer may be used for both functions.

As previously mentioned, the outlet nozzle 13 of the drying apparatus may be moveable with respect to the housing 10 so that the warm-air flow can conveniently be directed over the face or other body parts of a user in order to effect drying of those parts.

In these circumstances, it is envisaged that the sensor unit may be carried or otherwise moved by the nozzle so that the survey region thereof is redirected in accordance with the position of the nozzle to sense the presence of the user's head etc. Alternatively, the sensor unit may remain stationary and be arranged to sense the presence in the survey region of the user's body adjacent the drying apparatus irrespective of which body part is actually to be dried.

Claims (11)

1. Warm-air drying apparatus for drying hands comprising electrically-operable blowing and heating means which is energisable to produce a flow of warm air, and means for sensing the presence of an object in proximity to the apparatus and within a predetermined region that is spaced from the apparatus and adjacent an outlet for said warm air, which is arranged to energise the blowing and heating means only in response to the presence of an object in said region being sensed thereby.

2. Warm-air drying apparatus according to Claim i,wherein the blowing and heating means are contained in a housing of the apparatus.

3. Warm-air drying apparatus according to Claim 2, wherein the sensing means is contained within said housing.

4. Warm-air drying apparatus according to any one of the preceding claims, wherein the sensing means includes meansfortransmitting a pulse signal, means for receiving a reflection of said pulse signal from a proximal object, and discriminator means which defines a predetermined time period following transmission of a said pulse signal and which is arranged to generate an output signal for controlling energisation ofthe blowing and heating means in response to a said reflected pulse signal being received during said predetermined time period indicative of the presence of a said object within said region.

5. Warm-air drying apparatus according to Claim 4, wherein the discriminator means is arranged such that the said predetermined period of time commences a finite time after transmission of a said pulse signal by said transmitting means and terminates a set time thereafter.

6. Warm-air drying apparatus according to Claim 4 or Claim 5, wherein the transmitting means is arranged to generate a series of pulse signals.

7. Warm-air drying apparatus according to Claim 6, wherein the said predetermined period of time is defined during the interval between transmission of each successive pair of pulse signals.

8. Warm-air drying apparatus according to any one of Claims 4 to 7, wherein said pulse signal comprises an ultrasonic signal.

9. Warm-air drying apparatus according to any one of the preceding claims, wherein the apparatus includes timing means which is arranged to energise the blowing and heating means for a predetermined duration in response to the presence of a said object in the proximity of the apparatus being sensed by the said sensing means.

10. Warm-air drying apparatus according to any one of the preceding claims, wherein said blowing and heating means comprises an electric-motor driven blower and an electrical resistance heating element.

11. Warm-air drying apparatus substantially as hereinbefore described with reference to the accompanying drawing.