STEAM CLEANING APPLIANCE

The present invention relates to a steam cleaning apparatus. In particular the present invention relates to a steam cleaning apparatus which can be used for cleaning when disconnected from an external source electrical power.

Steam cleaning appliances having become increasingly popular over the last few years. An example of such a steam cleaning appliance is a steam cleaning mop for cleaning tiled or hardwood floors. Handheld steam cleaning appliances can be used for cleaning work surfaces such as in the kitchen.

A steam cleaning appliance comprises a boiler which transfers sufficient heat energy to water in order to convert it into steam. The steam is then directed via a steam cleaning head to the surface which is to be cleaned. Current steam cleaning appliances are powered by an external source of electricity which supplies energy to an electrical heating element in a boiler. A problem with using an external source of electricity is that the steam cleaning appliance must be connected by an electrical cord to the electricity power supply. This means that the steam cleaning appliance is tethered to the electricity socket and the user can only use the steam cleaning appliance within a certain distance of the electricity socket. A steam cleaning appliance according to the preamble of claim 1 is already known e.g. from US-A-2005022333. EP1795108 discloses a cleaner having a steam generator having an external power supply for supplying AC electricity to a steam generator. The cleaner also has a battery which may be charged from the AC power supply. The battery can supply power to the steam generator and generate steam once the AC power supply is disconnected.

A problem with using a battery to supply power to a steam generator is that energy is required to raise the ambient temperature of the water and a significant amount of energy is required to change the phase of water from liquid to steam. The energy stored in a battery is limited and this will mean that there may be a very short runtime when the steam cleaner is solely running on a battery.

US 2013/0312212 discloses a steam generating device which comprises a fuel powered heater for heating water from a reservoir into steam. The heater includes an igniter in fluid communication with a combustion chamber. The fuel, typically butane or propane is burnt in the combustion zone and the heat from burning the fuel is used to turn the water into steam. Using butane or propane to heat the water means that the steam generating device can be cordless. However the steam generating device will require a supply of combustible fuel which will need replacing regularly. A user may not wish to use a fossil fuel to power a steam cleaner because the steam generating device will exhaust noxious fumes. Furthermore a user may not even be allowed to use the steam generating device in some sensitive areas because the device requires an ignition source.

Embodiments of the present invention aim to address the aforementioned problems.

According to an aspect of the present invention there is a steam cleaning appliance comprising: a water tank; a boiler in fluid communication with the water tank, the boiler comprising a boiler water input for receiving water from the water tank and a boiler superheated steam output for exhausting superheated steam and a water heating path connected between the water input and the superheated steam output; and a steam cooling element comprising a superheated steam input in fluid communication with the superheated steam output; a wet steam output; and a steam cooling path between the superheated steam input and the wet steam output; wherein the steam cooling element is arranged to transfer heat away from the superheated steam and cools the superheated steam into reduced enthalpy steam or reduced enthalpy steam or wet steam as the superheated steam flows along the steam cooling path.

This means if the boiler superheats steam, thermal energy can be extracted from the steam before it leaves the steam head. This prevents the superheated steam from damaging any plastic components or plastic housing of the steam cleaning apparatus. This also makes the steam cleaning apparatus safer in the domestic environment.

Preferably the boiler comprises a solid thermal heat store and at least one electrical heating element is embedded in the boiler. Preferably the boiler comprises a solid thermal heat store and the water heating path comprises at least one conduit embedded in the boiler. Preferably the boiler is in thermal contact with a thermal heat store. The thermal heat store is a thermal mass which stores thermal energy which is to be supplied to the boiler. Preferably the boiler comprises a water heating circuit which is in thermal contact with the thermal heat store. Preferably the water heating circuit is embedded or surrounded in the thermal heat store. The thermal heat store can be any means suitable for storing thermal energy. Preferably the thermal heat store is heated with an electrical heating element. Preferably the electrical heating element is embedded or surrounded in the thermal heat store. Preferably the thermal heat store is configured to be heated to between 300 °C to 425 °C. Preferably the thermal heat store is in a solid phase.

Preferably the temperature of steam at the steam inlet is greater than the temperature of steam at the steam outlet. Preferably steam at the steam inlet is superheated steam. This means that sufficient energy can be recovered from the superheated steam in order to warm the cold water from the water tank.

Preferably steam cooling element comprises a water inlet in fluid communication with the water tank; a water outlet in fluid communication with the boiler water input of the boiler; a water flow path between the water inlet and the water outlet, a steam inlet in fluid communication with the boiler superheated steam output of the boiler; a steam outlet in fluid communication with the steam head; a steam flow path between the steam inlet and the steam outlet; and a heat exchanger between the water flow path and the steam flow path for transferring heat from steam output from the boiler to water supplied from the water tank. In this way the recovered thermal energy can be used to preheat the cold water from the water tank. This improves efficiency of the boiler because energy is not wasted delivering over heated steam to a cleaning surface.

Preferably the water flow path and / or the steam flow path are labyrinthine. This means that the water and the steam do not take a direct route through the heat recovery element and more thermal energy can be transferred between the steam and water.

Preferably the water flow path is adjacent to a first surface of the heat exchanger and the steam flow path is adjacent to a second surface of the heat exchanger. This means thermal energy is transferred through the heat exchanger itself. Preferably the heat exchanger is relatively thin compared to the thickness of the heat recovery element. This ensures that the thermal energy transfer is improved.

Preferably the heat recovery element comprises first disc comprising the water inlet, water outlet and water flow path therebetween and a second disc comprising the steam inlet, the steam outlet and the steam flow path therebetween and the heat exchanger is positioned between the first and second discs. In this way the heat recovering element has a circular cross section.

Preferably the heat exchanger comprises radiating fins protruding into the water flow path and / or the steam flow path. The radiating fins increase the surface area that the water and the steam flow over in the heat recovery element. This increases the thermal energy transfer between the steam and the water in the heat recovery element.

Preferably the heat recovering element comprises a first inner chamber and a second outer chamber surrounding the first inner chamber and the water flow path is in the first inner chamber and the steam flow path is in the second outer chamber or the steam flow path is in the first inner chamber and the water flow path is in the second outer chamber. Preferably the first inner chamber and the second outer chamber are substantially cylindrical.

Preferably the steam cooling element dissipates thermal energy to the local surroundings. In this way the excess thermal energy is not recycled. Preferably the steam cooling element is air cooled. Preferably the steam cooling element comprises a radiator for radiating thermal energy away from the steam cleaning appliance. Preferably the housing of the steam cleaning appliance comprises air holes for assisting air cooling of the steam cooling element.

Preferably the steam cooling element comprises a valve for selectively cooling all or a proportion of the steam exiting the boiler. Preferably the valve is operated mechanically, electronically or electromechanically. Preferably the valve is mechanically coupled to a bistable element which is arranged to operated the valve at a predetermined temperature threshold. Preferably the valve is coupled to an electronic solenoid which is electrically connected to a control circuit having a temperature sensor for sensing the temperature of the superheated steam. By selectively cooling the superheated steam the cooling can be better regulated and the temperature of the reduced enthalpy steam or wet steam exiting the floor head can be better controlled.

Preferably the steam cleaning appliance is a steam mop.

According to another aspect of the present invention there is a method of providing a water tank; a boiler comprising a boiler water input for receiving water from the water tank and a boiler superheated steam output for exhausting superheated steam and a water heating path connected between the water input and the superheated steam output; a steam cooling element comprising a superheated steam input; a wet steam output; and a steam cooling path between the superheated steam input and the wet steam output; wherein the steam cooling element is arranged to transfer heat away from the superheated steam and cools the superheated steam into reduced enthalpy steam or reduced enthalpy steam or wet steam as the superheated steam flows along the steam cooling path; coupling the boiler water input to the water tank; and coupling the boiler superheated steam output to the superheated steam input.

Various other aspects and further embodiments are also described in the following detailed description and in the attached claims with reference to the accompanying drawings, in which:

• Figure 1 shows a perspective view of the steam cleaning appliance;
• Figure 2 shows a cross sectional view of the steam cleaning appliance;
• Figure 3 shows a perspective view of a steam generating apparatus;
• Figure 4 shows a cross sectional view of a steam cooling element;
• Figure 5 shows a schematic diagram of the steam cleaning appliance;
• Figure 6 shows another cross sectional view of a steam cooling element;
• Figure 7 shows a temperature enthalpy diagram for steam;
• Figure 8 shows a schematic diagram of a steam cleaning appliance;
• Figure 9 shows a cross sectional view of a steam cooling element;
• Figure 10 shows a schematic diagram of a steam cleaning appliance;
• Figure 11 shows another schematic diagram of an alternative steam cleaning appliance;
• Figure 12 shows yet another schematic diagram of an alternative steam cleaning appliance;
• Figure 13 shows another schematic diagram of an alternative steam cleaning appliance;
• Figure 14 shows a partial cross sectional view of a floor head of a steam cleaning appliance;
• Figure 15 shows another partial cross sectional view of a floor head of a steam cleaning appliance; and
• Figure 16 shows a schematic diagram of a simple alternative steam cleaning appliance.

Figure 1 shows a perspective view of a steam cleaning appliance 10. The steam cleaning appliance can be any appliance for generating steam for cleaning surfaces. Figure 1 shows an exemplary steam mop 10 which is a non-limiting example of a steam cleaning appliance. Hereinafter the term steam mop will be used to describe the steam cleaning appliance, but the present invention can be applicable to steam cleaning appliances other than steam mops.

The steam mop 10 comprises a steam head 12 for delivering steam to a surface to be cleaned. Typical surfaces are tiled floors or hardwood floors, but other surfaces may be cleaned with the steam mop 10. The steam head 12 may comprise a pad or cloth (not shown) fixed to the underside of the steam head 12 to pick up dirt dislodged by the steam cleaning action.

The steam head 12 is coupled to a body 14 by an articulated joint 16. The articulated joint 16 may comprise a universal joint for allowing at least two degrees of freedom between the steam head 12 and the body 14. The articulated joint 16 is hollow and comprises a steam duct (not shown) for delivering steam to the steam head 12.

The body 14 of the steam mop may comprise a clam shell construction. The two halves of the clam shell are fixed together with screws and encase a steam generating apparatus 24. The steam generating apparatus 24 is not shown in Figure 1, but will be described in further detail in the subsequent Figures.

The body 14 is coupled to a water tank 18 for holding a water reservoir. The water tank 18 is in fluid communication with the steam generating apparatus 24. The water tank 18 may be removable for allowing the user to refill with water.

A handle 20 is coupled to the body 14 and provides a grippable portion for the user to hold during use. The body 14 and the handle 20 may have controls for operating the steam mop. The controls are coupled to an electronic controlling circuit (not shown). The steam mop 10 comprises an electrical heating circuit 60 which may be electrically coupled to a power cord (not shown) for connecting to an alternating current (AC) electricity supply. The AC electricity supply is configured to deliver electrical energy to the steam generating apparatus 24. In some embodiments a power cord is not needed because the steam mop 10 electrically and physically couples with a docking and charging station. In some alternative embodiments, the steam mop may be powered by a DC electricity supply such as a battery (not shown).

Turning to Figure 2, which shows a schematic cross sectional diagram of the steam generating apparatus 24 will be described in further detail. The steam generating apparatus in some embodiments is a boiler 24 and will be referred to hereinafter as a boiler. The boiler 24 comprises a resistive electrical heating element 26. The ends 28 of the resistive heating element 26 are electrically coupled to the electric heating circuit 60.

The resistive heating element 26 is embedded in a solid thermal mass 30. The thermal mass 30 is configured to be heated by the resistive heating element 26. By heating the thermal mass 30 with the resistive heating element 26, electrical energy is converted to thermal energy and the thermal energy is stored in the thermal mass. A portion of a water heating circuit 32 is also embedded within the thermal mass 30. The water heating circuit 32 provides a water heating path across the boiler 24 extending from a boiler water input 45 to a boiler superheated steam output 47. As the water flows through the water heating path, the water is heated and turned into steam. In some embodiments the water heating circuit 32 is a helical coil 33, however in other embodiments the water heating circuit 32 may have a conduit following a different path through the thermal mass. Ideally the water heating circuit 32 traces a circuitous route through the thermal mass heat the water to a sufficient degree. This also aids draining the thermal energy from the thermal mass 30. In some embodiments the thermal mass 30 is integral with the boiler 24. This means that if the thermal mass 30 is not a good thermal conductor, the thermal mass immediately surrounds the water heating circuit 32 and the resistive heating element 26. In other embodiments the thermal mass 30 may be distal from the boiler 24 in which case the thermal mass 30 is made from a good thermal conductor such as copper.

In some embodiments, the thermal mass is a cylinder or substantially cylindrical. By using a cylinder, the thermal energy density of the thermal mass 30 can be increased over other volumes such as cubes or cuboids. In another embodiment the thermal mass is spherical in shape. However a cylinder is preferable because the helical coil 33 is easier to manufacture and embed in a cylinder.

The thermal mass 30 in some embodiments is a good thermal conductor so that the thermal energy can be transferred away from thermal mass 30 to the water heating circuit 32. In some embodiments the thermal mass 30 comprises a metal material although the thermal mass can be any material suitable for storing thermal energy.

The resistive heating element 26 heats the thermal mass 30 up to an initial operating temperature. The initial operating temperature is close but below the melting point, for example at about 400°C, of the material of the solid thermal mass. Preferably in some embodiments the thermal mass is heated between 400 - 425 °C.

In some alternative embodiments, the thermal mass 30 can be heated through a solid to liquid phase change. In this way the thermal mass stores not only the thermal energy required to raise the temperature of the thermal mass from an ambient temperature to 400°C. This means latent energy which changes the phase of the thermal mass 30 is also stored. By storing latent energy in the thermal mass 30, far more energy can be stored in the thermal mass 30 without raising the actual temperature of the thermal mass 30.

When the thermal mass 30 is heated to its initial operating temperature, the resistive heating element 26 is no longer needed to heat the thermal mass 30. At this point, the thermal mass 30 stores enough energy to heat and power the boiler 24 without an additional heating source. This means that the steam cleaning device 10 can be used remote from an electrical power source. As the water is converted into steam by the boiler 24, the temperature of the thermal mass 30 is reduced as the boiler 24 depletes the thermal energy from the thermal mass 30.

As the water flows from the boiler water input 45 to the boiler superheated steam output 47 through the water heating path in the water heating circuit 32 in the boiler 24, the temperature of the water increases in the boiler 24. The water eventually approaches its boiling condition and some molecules attain enough kinetic energy to reach velocities that allow them to escape from the liquid. At this point if the pressure remains constant, adding more heat does not cause the temperature to rise any further, but causes the water to form saturated steam. The temperature of the boiling water and the saturated steam are the same but the energy per unit mass is much greater in the steam.

Reference is now made to Figure 7 which shows a temperature enthalpy phase diagram for water. Steam with a temperature equal to the boiling point at that pressure is known as dry saturated steam. However to produce 100% dry steam in a boiler is rarely possible and the steam will usually contain droplets of water. Turning to Figure 7 the water in the water tank 18 will usually be at room temperature at about 20°C and in the condition labelled A. As the water is heated in the boiler 24, the water will follow the saturated water line until it has received all of its liquid enthalpy h_l as indicated by the label B. When further heat is added, the water changes phase to a water/vapour mixture and continues to increase in enthalpy while remaining at the saturation temperature, which in this case is 100°C.

As heat is added to the water / vapour mixture, the water / vapour mixture increases in its dryness. Dryness is determined by the ratio of the water to the vapour in the water / vapour mixture. For example at B, the dryness is equal to 0. At C 100% of the water has been converted to vapour and the dryness is equal to 1. A point exactly halfway between the water / vapour conditions at B and C, the dryness will be 50%.

Once all of the water has received all of its enthalpy of evaporation, the water is completely vapour and it reaches the dry saturated steam line. If the steam continues to be heated after this point whilst the pressure remains constant, the temperature of the steam will rise. For example the temperature of the steam will rise to a point such as indicated by label D. Steam heated above the dry saturated steam line is superheated steam.

Superheated steam in a steam cleaning product can be problematic because the superheated steam can be at a temperature in excess of the temperature at which plastic melts. This means that a floor head 12 needs to be made from a material which can withstand high temperatures. In some cases the superheated steam can exceed 400°C at which point most plastics will melt. Plastic materials which do not melt at this temperature are specialised and expensive. Furthermore reducing the temperature of the superheated steam is desirable because this is safer for the user. Superheated steam is invisible and this means that the user can easily hurt themselves on superheated steam. By reducing the temperature of the steam such that the steam is reduced enthalpy steam or wet steam (a mixture of water / vapour), the steam is visible and less dangerous.

In addition the inventors have realised that wet steam can be useful for the purposes of cleaning due to the increased level of moisture. The condensation of the vapour releases the stored enthalpy of condensation as the wet steam transitions from a condition at C to a condition at B, which in turn heats up the surface to be cleaned. Heating the surface to be cleaned is preferable because germs are killed at higher temperatures, for example above 72°C.

In order to achieve a useful runtime with the boiler 24 using energy from the thermal mass 30, the thermal mass 30 needs to be heated to a temperature which is significantly higher than the boiling point of water. This means that the boiler will operate at a very high temperature and generate superheated steam at the boiler superheated steam output 47 when water flows though the water heating path.

Embodiments hereinafter discuss different way of mitigating superheated steam being produced by a boiler 24 with a thermal mass 30 with an initial operating temperature much greater than the boiling point of water.

Turning back to Figure 2, the thermal mass 30 is surrounded with an insulating jacket 34 which limits heat loss from the external surfaces of the thermal mass 30. The insulating jacket 34 comprises two halves which couple together to completely encase the thermal mass. The insulating jacket 34 is made from a ceramic material but the insulating jacket can be made from any suitable insulator.

A thermostat or thermocouple 36 is also embedded in the thermal mass 30 for determining the temperature of the thermal mass 30. The thermostat 36 is coupled to the electronic controlling circuit (not shown) and the electronic controlling circuit switches off the electrical power to the heating element 26 once the thermal mass reaches a predetermined temperature.

The predetermined temperature of the thermal mass is selected on the basis that the thermal mass stores sufficient thermal energy to convert a required mass of water to steam without supplying further energy to the thermal mass. In this way the steam mop 10 can be heated up with an AC electricity supply and then used remotely without an electricity supply.

Since the thermal mass 30 has to be heated in excess of the boiling point of water, the superheated steam initially exits the boiler 24 at the boiler superheated steam output 47. The superheated steam is unnecessary for the application of domestic steam cleaning and the temperature of the superheated steam is reduced until it becomes reduced enthalpy steam or wet steam. By reducing the temperature of the superheated steam such that it is wet steam, the steam cleaning device can be made with conventional plastics material which can withstand the lower temperature of the reduced enthalpy steam or wet steam.

In some embodiments optionally the thermal energy is recovered from the superheated steam. As will be understood in reference to other embodiments, it is not necessary to recover the thermal energy from superheated steam in order to reduce the temperature of the superheated steam. However recovering energy from the superheated steam means that energy is conserved and the steam mop has a longer run time.

The water heating circuit 32 will now be discussed in reference to Figure 3. Figure 3 shows a schematic perspective view of the steam generating apparatus 22 without the thermal jacket 34.

Water is supplied from the water tank 18 to the steam generating apparatus 22 by cold water tube 38. The cold water tube 38 is coupled to a steam cooling element 40. The embodiment as described in reference to Figure 3, the steam cooling element 40 is also a heat recovery element 40 and the cold water tube is coupled via water inlet 42 (best seen in figure 4). The water then flows out of the heat recovery element 40 via water outlet 44. The water outlet is coupled to and in fluid communication with the embedded helical coil 33 via a boiler water input 45. As the water flows through the helical coil 33, the water heats up and is converted into steam. The other end of the helical coil 33 comprises a boiler superheated steam output 47 and the boiler superheated steam output 47 is coupled to and in fluid communication with a steam inlet 46 of the heat recovery element 40. Reduced enthalpy steam or wet steam passes out of the heat recovery element 40 via steam outlet 48. The steam outlet 48 is coupled to the steam head 12 via conduit 50.

Turning to figure 4, the heat recovery element 40 will now be discussed in greater detail. Figure 4 shows a schematic cross sectional view of the heat recovery element. The heat recovery element 40 comprises a first chamber 52 in fluid connection with the water inlet 42 and the water outlet 44. The water flows from the water inlet 42 to the water outlet 44 and the water flow path, as shown by dotted line A is located in the first chamber 52. The heat recovery element 40 comprises a second chamber 54 in fluid connection with the steam inlet 46 and the steam outlet 48. The steam flows from the steam inlet 46 to the steam outlet 48 and the steam flow path, as shown by dotted line B is located in the second chamber 54.

The first and second chambers 52 and 54 share a common wall 56. Wall 56 is a heat exchanger and heat from the steam flow is recovered. Thermal energy is transferred from the steam, across the heat exchanger 56 and to the water. In this way the exiting superheated steam is cooled by the cold water from the water tank 18 and the cold water is warmed by the superheated steam. The superheated steam is cooled from a temperature in excess of 200°C to a temperature between 100°C and 140°C wherein the superheated steam is converted to reduced enthalpy steam or wet steam. By recovering energy from the steam, the boiler 24 has to heat the water up less and so less energy is required to turn the water into steam. The heat exchanger 56 separates the water flow path and the steam flow path such that the first and second chambers 52 and 54 are not in fluid communication across the heat exchanger 56. The heat exchanger 56 permits transfer of thermal energy from the hot steam to the cold water.

In some embodiments the heat recovery element 40 has a circular cross section and the heat exchanger 56 is disc shaped. In other embodiments the heat recovery element 40 can be any suitable shape.

In some embodiments the water flow path A and the steam flow path B in the heat recovery element 40 have a labyrinthine pathway. This means that the flow path of the steam and the water cross an increased surface area of the heat exchanger 56 and the heat transfer is increased.

The heat exchanger 56 comprises protruding radiating fins 58. In some embodiments the radiating fins are a plurality of concentric rings upstanding from the surface of the heat exchanger 56. The radiating fins protruded into the water flow path and the steam flow path and increase the surface area of the heat exchanger 56. The heat exchanger 56 is made from a thermally conductive material such as metal.

Operation of the steam mop 10 will now be discuss in reference to Figure 5, which shows a schematic flow diagram of the steam mop 10. First the user turns the steam mop 10 on. This connects the electrical heating circuit 60 to an AC electrical supply 66. The electrical heating circuit 60 is coupled to the resistive heating element 26. The heating element 26 heats the thermal mass 30 of the steam generating apparatus 22 until the thermal mass 30 reaches a predetermined temperature (e.g. 400°C). As mentioned above, the thermal mass 30 is thermally coupled to the boiler 24 because the thermal mass 30 is integral with the boiler 24. At this point the steam mop 10 is fully charged and the user can use the steam mop 10. A user may then disconnect the steam mop 10 from the electrical supply 66.

Water is stored in a water tank 18. When the user operates the steam mop 10 an internal battery 64 powers a pump 62. The pump 62 pumps water from the water tank 18 to the heat recovery element 40 via the water inlet 42. The cold water passes over the heat exchanger 56 and the cold water absorbs the thermal energy from the hot heat exchanger 56. The warm water exits the heat recovery element 40 via the water outlet 44. The warm water then passes through the water heating circuit 32 comprising the helical coil 33 and is converted into superheated steam in the boiler 24. The superheated steam enters the heat recovery element at steam inlet 46. The superheated steam passes over the heat exchanger 56 and dissipates thermal energy to the heat exchanger 56 which cools the steam. Cooler reduced enthalpy steam or wet steam then exits the heat recovery element 40 at steam outlet 48 and the wetsteam is delivered to the steam head 12.

Figure 6 shows an alternative embodiment of the heat recovery element 40. The same numbering has been used to show the same elements as in the previously described embodiments. The heat recovery element 40 is essentially the same as in the previously described embodiments except the geometry of the first and second chambers 52, 54 is different. The first chamber 52 is an inner cylindrical bore. The second chamber 54 is an outer cylinder surrounding the first chamber. In this way the wall of the inner cylindrical bore is the heat exchanger 56.

Another embodiment is shown in Figure 8. Figure 8 shows a schematic representation of an alternative arrangement for a steam cooling element 40 having a heat recovery element 40. The components which are the same as previously described embodiments have been labelled with the same reference numbers. The boiler 24 comprises an internal member 70 and an outer cap 72 which fits over the internal member 72. The internal member 70 comprises one or more resistive heating elements embedded therein. The internal member 70 comprises a circumferential groove which defines a helical or spiral water heating path around the internal member when the outer cap 72 is in place. Superheated steam exits the boiler 24 and enters a heat recovery element 74. The heat recovery element 74 is similar to the embodiment as discussed in reference to Figure 6 except that the cold water inlet 42 and the warm water outlet are inclined at an angle to a longitudinal axis to the heat recovery element 74. In other embodiments the inputs and outputs of the steam cooling element can be orientated at any angle to each other.

Figure 9 shows a cross sectional view of an alternative embodiment with a modified heat recovery element 74 of Figure 8. The components which are the same as previously described embodiments have been labelled with the same reference numbers. The modified heat recovery element 74 comprises two first or outer chambers 75, 76 which surround the second chamber 54. An electronically controlled valve 78 is mounted between the two first outer chambers 75, 76. In a first mode the valve 78 is open. In the first mode the two first chambers 75, 76 are in fluid communication and the cold water surrounds the whole of the second chamber. In the first mode the heat recovery element 74 operates at full capacity and transfers the maximum thermal energy. In a second mode the valve 78 is closed and the outer chambers 75, 76 are separated from each other. In this case the cold water only flows through the top half of the heat recovery element 74 one of the outer chambers 75. In this case the heat recovery element operates at a reduced rate of thermal transfer. The control of the valve is operated by an electronic solenoid coupled to a control circuit (not shown). The control circuit is coupled to a temperature sensor (not shown) which detects the temperature of the reduced enthalpy steam or wet steam exiting the heat recovery element. The control circuit opens the valve 78 if the reduced enthalpy steam or wet steam exiting the steam output 48 becomes too hot and closes the valve 78 if the reduced enthalpy steam or wet steam exiting the steam output 48 becomes too cold. The valve 78 can be used in conjunction with any of the other embodiments.

Figure 10 shows another embodiment of the present invention. Figure 10 shows a schematic diagram of an alternative steam cooling element comprising a heat recovery element. The steam cleaning device as shown in Figure 10 is the same as shown in the embodiments discussed in relation to previous embodiments except that the water tank and the steam cooling element have been modified. The components which are the same as previously described embodiments have been labelled with the same reference numbers. The heat recovery element 80 is mounted in the water tank 18. In this case the water in the water tank 18 is in direct contact with the outer surface of the heat recovery element 80. The heat recovery element 80 comprises fins 82 for increasing the surface area of the outer surface of the heat recovery element and improving the transfer of heat between the heat recovering element 80 and the water in the water tank 18, by placing the heat recovery element 80 in the water tank 18, the pipes and connectors between the boiler 24, pump 62 and water tank 18 are simplified.

Optionally a valve 84 is provided to selectively send steam to the heat recovery element 80. The valve is operable dependent on the temperature of the steam exiting the boiler 24 at the boiler steam outlet 47. A thermocouple, thermostat or other temperature sensor (not shown) may detect the temperature of the steam exiting the boiler. A valve control circuit (not shown) is connected to the temperature sensor and open or close the valve 84 with an electronic solenoid (not shown) dependent on the data received from the temperature sensor. If the steam is superheated then the valve 84 will direct all or a proportion of the superheated steam to the heat recovery element 80 otherwise the valve 84 will direct the steam directly to the floor head 12.

Figure 11 shows yet another embodiment according to the invention. Figure 11 shows a schematic diagram of an alternative steam cooling element comprising a heat recovery element. The steam cleaning device as shown in Figure 11 is the same as shown in the embodiments discussed in relation to previous embodiments except that the water tank and the steam cooling element have been modified. The components which are the same as previously described embodiments have been labelled with the same reference numbers. The heat recovery element 85 is the same as the embodiments discussed in reference to Figures 6 and 8. The heat recovery element comprises an inner steam chamber 52 surrounded by an outer water chamber 54. Water from the water tank 18 is pumped by pump 62 to the boiler 24. In addition the water tank 18 acts as a thermal siphon for delivering cold water to the heat recovering element 85 and removing warm water therefrom. The water tank 18 is physically located above the heat recovery element 85 during use so that the force of gravity can act on the cold water. The water tank 18 comprises a thermal siphon water outlet 86 the bottom water tank 18 which is in fluid communication with the water inlet 42 of the heat recovery element 85. The water tank 18 further comprises a thermal siphon water inlet 87 in fluid communication with the water outlet 44 of the heat recovery element. The thermal siphon effect draws warm water from the heat recovery element 85 and delivers cold water to the heat recovery element 85. In some embodiments the thermal siphon effect can be enhanced with a pump (not shown).

Figure 12 shows another embodiment according to the invention. Figure 12 shows a schematic diagram of an alternative embodiment with an alternative steam cooling element 90. For the purpose of clarity the connectors have been partially shown and A is in fluid communication with A and B is in fluid communication with B. The components which are the same as previously described embodiments have been labelled with the same reference numbers.

The steam cooling element 90 comprises a valve 91 and a heat regulator 92. The valve 91 comprises a cold water chamber 93 and a steam chamber 94. The cold water chamber 93 and the steam chamber are separated and not in fluid communication. The water chamber 93 is selectively in fluid communication to the water tank 18 via pump 62. The water chamber 93 is also in fluid communication with the heat regulator 92. The steam chamber 94 is in fluid communication with the floor head 12 and delivers reduced enthalpy steam or wet steam thereto. The steam chamber 94 receives cooled reduced enthalpy steam or wet steam from the heat regulator 92. The valve 91 comprises a mechanically or electronically operate valve element 95. The valve element 95 in some embodiments is a plunger 95 for selectively blocking a water flow path in the water chamber 93. The plunger 95 is mechanically moved by a bimetal plate 96 which deforms and moves the plunger 95 to an open position when the bimetal plate 96 is heated to a predetermined temperature. Alternatively, the bimetal plate 96 can be replaced with a temperature sensor, servo mechanically coupled to the plunger 95 and control circuit for controlling the servo. Alternatively in some other embodiments there is an electronic solenoid coupled to the control circuit for operating the valve.

The heat regulator 92 comprises a steam cooling path which guides the superheated steam. Part way along the steam cooling path, water is introduced into the superheated steam to cool it down. This will now be described in further detail.

When the plunger 95 is in the open position, water flows from the valve 91 to the heat regulator 92 as shown by arrows labelled A. Water is then introduced into the flow of the superheated steam from the boiler 24. The water as it mixes with the superheated steam is heated up itself and is turned into steam itself. The latent heat required to turn the water to steam, reduces the temperature of the superheated steam until it becomes cooler reduced enthalpy steam or wet steam. When the temperature of the reduced enthalpy steam or wet steam is reduced sufficiently below the predetermined temperature, the bimetal plate 96 moves the plunger 96 into a closed position. This shuts off the water flow from the valve 91 to the heat regulator 92 and the temperature of the steam rises again until the valve 91 opens again. The feedback loop between the valve 91 and the heat regulator 92 means that heat is not wasted because all the steam received at the floor head 12 is reduced enthalpy steam or wet steam at a desired temperature. In this way the steam cooling element 90 recovers energy from the superheated steam to convert a small portion of water into reduced enthalpy steam or wet steam.

Alternatively the bimetal plate is replaced with a the control circuit which detects the temperature with the temperature sensor. If the temperature of the steam in the valve 91 is too hot the control circuit opens the plunger 95 with electronic solenoid. When the temperature sensor detects that the temperature of the steam has fallen, the control circuit closes the punger with the electronic solenoid.

A further embodiment will now be described in reference to Figure 13. Figure 13 shows a schematic representation of an alternative embodiment according to the invention. The components which are the same as previously described embodiments have been labelled with the same reference numbers. The embodiment shown in reference to Figure 13 is the same as the embodiments as described in reference to Figure 11 except that the steam cooling element 100 is coupled to a radiator 102. Excess heat from the superheated steam is radiated away to the air via radiator 102. In this embodiment the steam cooling element 100 does not recover the thermal energy from the superheated steam and the thermal energy is dissipated to the environment external to the steam cleaning apparatus.

Figure 14 shows another example of an embodiment according to the invention. Figure 14 shows a partial cross sectional view of the floor head of the steam cleaning apparatus according to the invention. The components which are the same as previously described embodiments have been labelled with the same reference numbers. The superheated steam is output from the boiler (not shown in figure 14) to the floor head via hose 102. The end of the hose outputs the superheated steam against an aluminium diffuser 104 and flows along a steam cooling path adjacent to the aluminium diffuser 104. The superheated steam is cooled when it comes into thermal contact with the aluminium diffuser 104. The aluminium diffuser 104 is air cooled and dissipates the thermal energy to the local surroundings. The top of the diffuser 104 is covered with a ceramic shield 106 which protects the plastic housing of the floor head 12. Once the steam has been cooled, the steam is outputted from the floor head 12 in a similar way to the other embodiments.

Figure 15 shows another alternative embodiment according to the invention. The components which are the same as previously described embodiments have been labelled with the same reference numbers. Figure 15 shows a partial cross sectional view of the floor head of the steam cleaning apparatus. The floor head 12 is similar to the floor head as described in the previous embodiments. The boiler 24 is pressurised and outputs pressurised superheated steam into an expansion chamber 108 close to the floor head 12. When the pressurised superheated steam enters the expansion chamber 108, the superheated steam is allowed to expand until it is at atmospheric pressure. The superheated steam is cooled as it expands and cooler, reduced enthalpy steam or wet steam is then delivered to the floor head.

Figure 16 shows an alternative embodiment according to another embodiment of the invention. Figure 16 shows a schematic diagram of a simple embodiment with a steam cooling element 40. The water is fed into the boiler 24 via a pump 62, although the pump 62 is optional and the water may be gravity fed to the boiler 24. The boiler 24 heats the water until it is superheated steam which is then fed into a steam cooling element 40. The steam cooling element comprises a steam cooling path 110 along which the superheated steam dissipates thermal energy and the superheated steam cools into reduced enthalpy steam or wet steam. The steam cooling element 40 can be any suitable means for transferring thermal energy away from the superheated steam. The steam cooling element can recover or dissipate the thermal energy. The cooler reduced enthalpy steam or wet steam is then output into the floor heat of the steam cleaning apparatus.

In another embodiment two or more embodiments are combined. Features of one embodiment can be combined with features of other embodiments.