This invention relates to a steam cleaner of the kind used in apparatus for domestic cleaning or sterilisation, particularly but not exclusively for cleaning or sterilisation of floor surfaces or flooring materials such as carpets, carpet tiles or matting.

Previously known steam generators comprise an electric element contained in a metal housing into which a flow of water is introduced. A pressurised jet of steam generated by contact with the heated metal is emitted from the housing through a nozzle. Although a jet of steam may give an appearance of active cleaning, an escape of steam is inefficient and creates unnecessary condensation.

According to the present invention, a steam cleaner comprises:

a housing;

a heating element disposed in the housing;

a passageway in the housing extending from an inlet to an outlet arranged so that water passing through the passageway may be heated by the element and converted into steam;

wherein the passageway comprises upper and lower sections;

each section comprising a core chamber and a peripheral chamber surrounding at least a part of the core chamber;

wherein the upper section is located in thermal contact with the heating element; the inlet communicating with the upper core chamber;

the upper core chamber communicating with the upper peripheral chamber;

the upper peripheral chamber communicating with a lower peripheral chamber; the lower peripheral chamber communicating with a lower core member; and the lower core member having one or more outlets communicating with an exterior of the housing.

Preferably, the peripheral chambers surround both sides and one end of the respective core chamber. The configuration of the passageway may be such that water passing into the inlet travels as water or steam successively through the core chamber, the upper peripheral chamber, the lower peripheral chamber, the lower core chamber and the outlet.

Preferably, the upper and lower peripheral chambers each surround the sides and at least one end of the respective core chambers, reducing any need for thermal insulation of the core chambers, particularly of the upper core chamber.

In use of the steam cleaner, water introduced through the inlet contacts heated surfaces of the upper core chamber, converting all or most of the water into steam. Steam and any remaining water passes through the upper peripheral chamber, after which no water should be present. The steam then passes downwardly through an opening into the lower peripheral chamber and then into the lower core chamber to the one or more outlets.

The location of the heating element adjacent the upper core chamber allows the outlet and lower surface of the housing to be at a relatively lower and safer operating temperature in comparison to the relatively high temperature required to convert water into steam in the upper core chamber.

Substantially all of the water is vaporised within the upper core chamber.

In a typical cleaner in accordance with this invention, the temperature in the upper core chamber may be about 250°C or higher, but the temperature in the upper and lower peripheral chambers may be about 110°C to about 150°C and the temperature in the lower core chamber and at the outlet may be about 110°C to about 120°C.

In preferred embodiments of the invention, an outlet nozzle is not used so that the pressure within the cleaner may not significantly exceed atmospheric pressure.

The upper core chamber preferably includes a multiplicity of baffles to provide a labyrinthine route between the inlet and outlet thereof, impeding any direct flow of water through the core chamber and also to increase the heat transfer area. The baffles may be arranged in rows with gaps to permit passage of fluid, a gap in one row facing a baffle in an adjacent row, so that water passing through a gap impinges on a heated surface in a subsequent row.

Preferably, a multiplicity of baffles may also be provided in the upper peripheral chamber to increase the heated transfer area.

In preferred embodiments, one or more barriers extend across the direction of fluid flow, upwardly from the floor of the passageway to prevent flow of liquid water between the chambers, for example between the upper core chamber and peripheral core chamber and between the upper and lower peripheral chambers. The barriers may be concave to retain water droplets during passage through the chamber. Alternatively an axial barrier may be curved to deflect droplets into channel shaped or concave outer barriers located downstream of the axial barrier. A labyrinth passageway is preferred to impede direct flow from the inlet to the outlet chamber. The barriers may take the form of weirs and serve to retain any liquid water in the higher temperature regions of the cleaner. The flow rate of water through the inlet may be controlled by selection and/or adjustment of the diameter of the inlet. A diameter from about 1.5 mm to about 2.5 mm, preferably about 1.8 mm to about 2.0 mm, most preferably about 2.0 mm, may be employed.

The floor of the upper chamber of the housing may be inclined to the horizontal, for example at an angle of 1° to 5°, preferably 1° to 2° in order to facilitate liquid flow in use.

A whistle may be provided to give an audible warning of a sufficient pressure level within the apparatus to allow efficient use.

The housing may be formed in two parts, releasably secured together to provide access to the interior of the upper section in order to facilitate cleaning and removal of limescale. Since the conversion of water to steam takes place in the upper section, build up of limescale in the lower section may not be encountered in use.

The steam cleaner may further comprise;

a housing;

a heating element disposed in the housing; a passageway in the housing extending from an inlet to an outlet arranged so that water passing through the passageway may be heated by the element and converted into steam;

wherein the outlet comprises an array of apertures located in the housing;

a flange extending downwardly from the housing, the flange surrounding the array of apertures and having a lip arranged so that the lip may contact a work surface to form an enclosure to contain steam emitted from the outlet in use.

The work surface may comprise a floor, carpet, floor covering or other surface which may require cleaning or sterilisation.

Preferably, the flange is rigid, that is made from material which is not sufficiently flexible to deform significantly during use. In preferred embodiments, the flange is composed of metal integral with a lower part of the housing.

Flexible materials have been found to be difficult to use when steam cleaning carpets or textile materials due to the high frictional forces which may be encountered.

The flange may be elongate in plan view so that steam cleaning may take place across a wide area of a substrate surface. The flange may be oblong, elliptical or oval in plan view. Alternatively the flange may have a rounded configurative rectangular.

A mounting for attachment of a mop head or brush head may be provided, the mop or brush head including an aperture dimensioned to receive the lip of the flange.

A steam cleaner in accordance with this invention confers several advantages. Use of an outlet nozzle is unnecessary, avoiding wasteful emission of steam into the air adjacent a surface to be cleaned. The high temperature components of the apparatus are shielded from contact with external fixtures or mounting, reducing any need for construction of the casing or other components from heat resistant materials. Thermal losses are also reduced. Use of a peripheral flange serves to retain steam in the volume created between the cleaner and a workpiece, preventing wasteful escape of steam and increasing the efficiency of cleaning and sterilisation.

The invention is further described by means of example, but not in any limitative sense, with reference to the accompanying drawings, of which:-

Figure 1 is a side elevation of a steam cleaner in accordance with this invention; Figure 2 is a perspective view from above of the cleaner shown in Figure 1 ;

Figure 3 is a perspective view from below of the cleaner shown in Figures 1 and 2; Figure 4 is an exploded view of the cleaner shown from above;

Figure 5 shows the cleaner housing with the top plate removed; and

Figure 6 is a plan view of the cleaner shown in Figure 5;

The Figures show a steam cleaner in accordance with this invention. The same reference numerals are used to denote like components in each Figure.

The cleaner comprises a housing (1) formed of metal and having a U-shaped passageway within which an electric heating element (2) is located. Contacts (3) allow the element to be connected to a power supply and control circuitry (not shown).

An upper plate (4) has a mounting for a thermal sensor (5) and an inlet (6) for a supply of water. A lower plate (7) has a linear array of apertures (8) and a mounting for a thermal sensor (9). The apertures (8) and sensor (9) are surrounded by a downwardly extending flange having a silicone gasket (10) having a generally planar lip (12) arranged in use to be located in contact with or adjacent a work surface to be cleaned. The cleaner has a passageway extending from the inlet (6) to the outlets (8). The passageway is divided into upper and lower sections. The upper section comprises an upper core chamber (13) and an upper peripheral chamber (14). The upper core chamber (13) extends generally lengthwise of the housing and contains rows of baffles (17) extending inwardly from the sides of the chamber and alternating baffles (28) located centrally of the chamber so that water passing from the inlet does not have a direct passageway through the core chamber. The heating element (2) is located beneath casing (29) so that maximum heating is delivered to the upper core chamber (13). An outlet (19) communicates with the upper peripheral chamber (14). The outlet (19) has a lip to reduce passage of liquid water from the core chamber (13). A barrier (18) forms a trap to retain water in the core chamber. The peripheral chamber (14) extends across the end and along the sides of the core chamber so that steam passing along it is heated by the element located beneath the casing (29). Barriers (27) in the form of weirs, located across the peripheral chamber (14) further prevent flow of any remaining liquid water from the upper section to the lower section through openings (22) extending downwardly into the lower section.

The lower section has a lower peripheral chamber (16) and a lower core chamber (15) having generally similar configuration to the upper chambers. Steam passing into the lower peripheral chamber passes to the inlet (20) into the lower core chamber (15). The lower core chamber (15) serves as a reservoir for steam passing to the outlet apertures (8). Steam passing through the outlet apertures (8) is retained in an enclosure (21) formed by the flange (10), the downwardly facing surface of the housing and a work surface against which the steam cleaner is placed in use.

The element may have a power rating of lkW to 1.2kW and a length of about 130 mm. A flow rate of 25-30 cm 3 per minute, typically 27 cm 3 per minute, may be employed. Water may be supplied to the inlet using a gravity feed, that is without the need for a pump.