GB2147804A - Hand drier - Google Patents

Abstract

A hand drier has a centrifugal fan (12) driven by a generally disc shaped motor (10) for circulating air inside a cowling (14). The cowling (14) has a rear wall, side walls extending from the rear wall to form a hood, and a front opening for receiving the user's hands. A cover (16) over the fan has central grille for admitting air from the central part of the interior space of the cowling to the centre of the fan, and an edge portion which forms the inner wall of an annular duct (20) directing air from the fan (12) over a heating element (22) and into the peripheral regions (26) of the interior space. The shape of the side walls is such that the air from the fan (12) is directed inwardly towards the central region (24) of the space for recirculation. The use of a cowling (14) and recirculatory air currents allows rapid drying of the hands by means of a relatively lower power motor and heating element. <IMAGE>

Description

SPECIFICATION Hand drier This invention relates to a hand drier of the kind which generates a stream of warm air for drying hands without physical contact.

Known hand driers of the above kind comprise a wall mounted casing containing a powerful electrically driven fan for driving air through an electrical heating element to a downwardly directed outlet or nozzle. The user places his or her hands in the stream, moving them around in the stream with palms facing alternately up and down until dry. Although generally effective and hygienic, such driers are relatively noisy in operation and consume a relatively large electrical current. The noise is particularly disadvantageous if several driers are in frequent use in a working area, as in, for example, food handling or medical areas where frequent washing is necessary for reasons of hygiene.

It is an object of this invention to provide an improved drier which is relatively quiet in operation.

According to this invention, a hand drier comprises an electric motor and a fan which drives air over a heating element and into a cowling. At least some of the heated air directed into the cowling is drawn by the fan from inside the cowling so that recirculation of heated air occurs. In a preferred embodiment of the invention, the fan is a centrigufal fan mounted at the rear of the cowling so as to draw air entirely from a central region of the cowling interior and to direct it back into the cowling interior in a peripheral region. Circulation of air in the interior thereby occurs from the peripheral region towards the central region. This may be assisted by providing the cowling with an inwardly curved outer lip.

Recirculation of heated air as opposed to blowing air exclusively out into the room results in a consider able reduction in the electrical heating power necessary, and since the air is contained largely within the cowling it is not necessary to produce a high velocity jet of air for effective drying. This allows a quieter, relatively low speed fan to be fitted. A further advantage resulting from this arrangement is that a comparatively inexpensive, low power motor can be used.

The invention will now be described by way of example with reference to the drawings in which: Figure 1 is a sectional side view of a hand drier in accordance with the invention; Figure 2 is a front view of the drier of Figure 1; Figure 3 is a front view of a fan for the drier of Figure 1; Figure 4 is a circuit diagram of the electrical circuit of the drier of Figure 1.

Referring to Figure 1, a preferred hand drier comprises a permanent magnet 'pancake' motor 10 carrying a disc-shaped centrifugal fan 12 mounted at the rear of a moulded polycarbonate cowling 14.

The fan 12 is covered by a grille 16, the perimeter of the grille and a motor mounting plate 18 together forming an annular duct 20 containing a wound electrical heating element 22 which extends around the circumference of the fan 12. The mounting plate 18 also forms a heat sink for the motor 10. The element 22 is a nichrome wire coil of approximately lOmm diameter with a total wire length of approximately 900mm. Air is collected by the fan 12 from the central region 24 of the cowling interior and blown out through the annular duct to peripheral regions 26 of the interior as shown by the dotted lines and arrows, circulation back to the fan 12 being assisted by the inwardly curved outer lip 28 of the cowling 14.

The shape of the cowling 14 can be more easily seen in Figure 2. The cowling 14 has a circular base SO for mounting on a wal, and tapers to an approximately elliptical front opening bounded by the lip 28. A preferred feature is a cut-out 32 at the bottom so that discarded rubbish is not collected in the cowling 14.

Referring to Figure 3, the centrifugal fan 12 comprises a disc S4 with raised blades 36. The blades 36 may be spiral or radial, and in the latter case have trailing curved tips which contribute to the reduced noise level of the drier.

In use the drier is switched on either by an external switch, or automatically using an infra-red sensor, and both hands are placed inside the cowling 14. Since heated air circulates inside the cowling and reaches the hands from all sides, it is not essential to rotate the hands to achieve complete coverage. The swirling hot air quickly dries the hands all over and between the fingers.

The basic electrical circuit of the drier is shown in Figure 4. The d.c. pancake motor M typically draws 4 to 6 amps at 10 to 15 volts. The series connected heating element R is of a resistance calculated to give the required voltage drop across the motor M without needing a voltage step-down transformer. This circuit diagram does not show such features as a timing and switching circuit, temperature sensitive cut-out, fuse, and infra-red hands sensor which the drier has in common with prior driers. All of the electrical circuitry is contained on a printed circuit board 40 (Figure 1) mounted behind the motor.

The pancake motor 10 was chosen primarily for its compactness. It has the additional advantage of relatively low inductance, allowing a relatively small smoothing capacitor across the mains power supply input for electrical interference suppression.

Being a relatively lightly loaded low speed motor, it is largely maintenance free.

In some meat and food processing industries, hygiene regulations call for washing of hands and arms to elbow height. The cowling 14 could be made large enough to accommodate both hands and arms in the folded position.

To summarise, a hand drier in accordance with the present invention has a centrifugal fan driven by a generally disc shaped motor 'or circulating air inside a cowling. The cowling has a rear wall, side walls extending from the rear wall to form a hood, and a front opening for receiving the user's hands.

A cover over the fan has central grille for admitting air from the central part of the interior space of the cowling to the centre of the fan, and an edge por tion which forms the inner wall of an annular duct directing air from the fan over a heating element and into the peripheral regions of the interior space. The shape of the side walls is such that the air from the fan is directcd inwardly towards the central region of the space for recirculation.

The use of a cowling and recirculatory air currents allows rapid drying of the hands by means of a relatively lower power motor and heating element.

Claims (11)

1. A hand drier comprising an electric motor and a fan arranged to drive air over a heating element and into a cowling shaped to accommodate the user's hands.

2. A hand driver according to claim 1, wherein the fan is arranged to draw air from the interior of the cowling.

3. A hand driver according to claim 1 or claim 2 wherein the cowling is shaped to direct air from the fan inwardly towards a central space in the cowling.

4. A hand drier according to claim 3 wherein the cowling has an inwardly directed outer lip.

5. A hand drier according to any preceding claim, wherein the cowling extends from a rear wall to a front opening, and wherein the fan is a centrifugal fan rotatable about an axis generally perpendicular to the rear wall and directed at the front opening.

6. A hand drier according to claim 5, wherein the fan is housed in a rear part of the cowling behind a cover, the cover having an edge portion which defines the inner wall of an annular duct for directing air from the fan towards the perimeter of the interior space of the cowling.

7. A hand drier according to claim 6 wherein the heating element is annular and mounted in the said duct.

8. A hand drier according to claim 6 or claim 7, wherein the cover extends over the whole of the fan and has a central grille for admitting air from the interior of the cowling to a central portion of the fan.

9. A hand drier according to any of claims 5 to 8, wherein the motor is generally disc shaped and mounted behind the fan.

10. A hand drier comprising a centrifugal fan mounted at the rear of a cowling so as to draw air from a central part of the interior space of the cowling and to drive the air over inner surfaces of the cowling to cause a circulation of air inside the cowling.

11. A hand drier constructed and arranged substantially as herein described and shown in the drawings.