GB2227821A - Devices for generating steam; wallpaper strippers - Google Patents

Abstract

A portable steam generator comprises a chamber 205 associated with a heating element 206 for heating water within the chamber in order to generate steam. The device comprises a main tank 201 for storing water. Steam from the chamber is replenished by water from the tank. This water may pass through an elongate passage or channel 242 on its way from the tank to the chamber. The capacity of the chamber is relatively small in relation to the tank thereby enabling a decrease in the heat-up time of the water within the chamber. The chamber may be within or adjacent the tank. A steam pad 50 is provided having an inlet 51 for receiving steam and means 55 for assisting distribution of the steam over the pad. A drainage outlet is also provided for permitting drainage of condensed steam away from the pad and return to the steam generator. <IMAGE>

Description

DEVICES FORGENERATING STEAM This invention relates to devices for generating steam. and in particular but not exclusively, to steam cleaners or wallpaper stripping apparatuses.

Conventional devices for generating steam generally comprise a large capacity tank containing a heating element. Such devices have the disadvantage that the water within the tank takes a long time to heat-up.

Another disadvantage is that the tank itself becomes very hot and requires insulation so as to reduce the risk of injury to the user.

It is an aim of the present invention to provide a mobile or portable device for generating steam which has a quicker heating-up time without the need to connect the device to a main water supply.

It is also an aim of the present invention to provide a device operative for heating sufficient water to provide the desired quantity of steam.

Devices of the above kind are frequently used in steam cleaning or wallpaper stripping apparatuses.

Conventional wallpaper stripping apparatuses employ a steam pad for distributing steam over an area of wallpaper to be stripped. Conventional steam pads have the disadvantage that condensed steam tends to spill from the steam pad onto the floor or onto the user.

It is also an aim of the present invention to provide a steam pad for a wallpaper stripping apparatus which overcomes this disadvantage.

According to the present invention, there is provided a mobile or portable device for generating steam1 comprising a chamber associated with a heating element for heating water within the chamber in order to generate the steam1 a tank for storing water1 and means for supplying water from the tank to the chamber, wherein the capacity of the chamber for heating the water is small relative to the capacity of the tank, thereby enabling a decrease in the heat-up time of the water in the chamber, and the chamber is disposed adjacent to or within the tank.

A one-way valve may be positioned within the means for supplying water for eliminating convective flow of heated water from the chamber through the means to the tank. A preferable alternative to the use of a one-way valve is to incorporate into the water supply means an elongate passageway so that water moving from the tank to the chamber must pass therethrough. The length of the passageway is such as to provide a degree of isolation between the cold water in the tank and the hot water in the chamber.

The elongate passageway may be in the form of a tube which extends into the tank.

Alternatively, the passageway may be formed integrally along a portion of the boundary between the tank and chamber. In this case, a channel may be formed in the wall along the edge of the chamber1 this channel being closed by the base of the tank and having one end opening into the tank and its other end opening into the chamber.

The provision of the elongate passageway enables the device to generate a relatively even flow of steam.

An insulating barrier is preferably provided on the surface of the cold water within the storage tank for preventing or reducing the quantity of steam condensing on the surface of the cold water. This improves the steam output from the device. The insulating layer may be of expanded close cell foam or a blow moulded mattress of air.

The chamber and the tank may be positioned so that during operation of the device at least some of the heat lost from the chamber can be used to heat the water stored in the tank.

The heating element may be in the form of an electrical element provided with a cut-out for electrically disconnecting the element when the temperature thereof exceeds a predetermined value.

The chamber may be disposed substantially centrally within the tank, the colder water within the tank serving as an insulator to protect the user from direct contact with the chamber.

Embodiments of the invention may be provided with an indicator for indicating the level or quantity of liquid within the tank and/or the chamber.

Embodiments of the invention may be of a modular construction whereby the tank is detachable from the chamber, and the supply means is such as to enable coupling of tanks of different capacity to the chamber.

A removable cap may be provided on the tank for enabling refilling of the tank. The cap is preferably provided with a steam release means for permitting a relatively slow and controlled release of steam from the tank as the cap is removed but before the cap becomes completely detached from the tank. The steam release means may be configured so that the released steam is directed away from any part of the cap likely to be held by the operator.

The cap is also preferably provided with pressure release valves for releasing pressure from within the tank when the steam pressure exceeds a desired level.

Embodiments of the invention may be incorporated in a steam cleaning or wallpaper stripping apparatus.

The steam cleaning or wallpaper stripping apparatus may be provided with a hose for coupling a steam outlet of the chamber to a steam pad or nozzle The hose may be attachable to a carpet cleaning1 upholstery cleaning, or curtain cleaning attachment.

Embodiments of the invention have the advantage that they are capable of generating steam quickly while retaining mobility owing to the use of a storage tank instead of the need to couple the device to a main water supply. Moreover, the use of a "cool" tank has the advantage that refilling or employing the device is safer and quicker owing to the relatively small volume of boiling water present in the device.

Embodiments of the invention therefore tend to be safer than conventional devices.

According to the present invention there is further provided a steam pad for a wallpaper stripping apparatus, comprising an inlet for receiving steam, means for assisting distribution of steam over the pad, and an outlet for permitting drainage of condensed steam from the pad.

The steam pad is preferably shaped so that condensed steam is directed towards the outlet during use.

The steam pad may alternatively be shaped so as to have a thin elongate nozzle for allowing access to restricted areas such as corners.

The outlet and the inlet may be substantially coaxial, the inlet being disposed centrally with respect to the outlet.

A hose may be provided for coupling the inlet of the steam pad to the steam generator. The hose preferably comprises an inner and an outer pipe, one disposed concentrically with respect to the other so that an annular passage is defined between the inner and outer pipes. In this case the inner pipe which can carry the steam from the generator to the pad is insulated from the user by the outer pipe. The outer pipe can also act as a return flow channel if connected to the steam drainage outlet.

Alternatively, the inlet and outlet may be adjacent to one another so that they may be coupled to respective hoses. The hoses may be substantially parallel to one another.

Steam pads according to the present invention have the advantage that they provide for the removal of condensed steam. The condensed steam may be returned to the tank of the device by the hose. This will have the effect of reducing the frequency with which the tank must be refilled.

A separate re-fill tank may be provided for collecting condensed steam, the separate tank being connected to the annular passage of the hose. The separate re-fill tank may also be detachable so that it can be used to carry water from a tap to the main tank.

This has the advantage that the steam generator tank can be filled from a relatively inaccessible tap, there being no need to lift the relatively bulky steam generator to the tap.

The invention will now be further described by way of example, with reference to the accompanying drawings.

in which: Figures la to ic illustrate a first embodiment of the present invention: Figure 2 illustrates a modification which may be applied to the embodiment of Figure 1: Figure 3 illustrates a second embodiment of the present invention Figures 4a and 4b illustrate a conventional steam pad: Figure 4c illustrates a steam pad according to an embodiment of the present invention: Figure 4d is a cross-sectional view of a hose which may be used with embodiments of the invention; Figure B illustrates various arrangements of props which may be used in conjunction with steam pads embodying the present invention:: Figure 6 is an alternative device for generating steam embodying the present invention; Figure 7 is a further alternative steam generating device according to the present invention; Figure 8 is an end view of the embodiment of Figure 7: Figure 9 is a sectional view of a handle of the embodiment of Figure 8 taken along the lines A-A; Figure 10 is a sectional view taken along the lines B-B of Figure 7; Figure 1.1 is a sectional view of a level indicator taken along the lines C-C of Figure 7; Figure 12 is an alternative form of steam nozzle:: Figure 13 is a sectional view of a tank and chamber according to a further embodiment of the present invention; Figure 1.4 is a perspective view of yet another steam generating device according to the present invention; Figure t5 is an exploded view of part of the embodiment of Figure 14; Figure 1.6 is a sectional view of an alternative form of tank and chamber which can be incorporated into embodiments of the present invention; Figure 17 is a perspective view of another tank and chamber arrangement which may be incorporated into embodiments of the invention; Figures 18a and 18b are respectively sectional and perspective views of a neck of the tank and a cap for engagement with the neck; and Figures 19a and 19b are exploded and sectional views respectively of the cap and a component of the cap illustrating pressure relief valves provided in the cap of the tank.

Figure la illustrates the first embodiment of the invention in which a device for generating steam comprises an open topped tank 1 having a cylindrical chamber 3 disposed centrally therein. The tank 1 is bolted to a base 5 by means of bolts 7. The base 5 and the bottom of the tank 1 define a cavity which houses wiring 11 of an electrical heating element 13. The electrical heating element 13 is sealingly supported in a hole, provided in the bottom of the tank 1, by an O ring 15. The wiring 11 can be connected to an electric power supply.

As illustrated in Figure ib, the open topped tank 1 can be filled directly from a tap 17. The open topped tank 1 is provided with handles 19 to assist carrying of the device.

One or more holes is provided at the lower end of the chamber 3 for permitting water 23 to pass from the tank 1 into the chamber 3. When the device is in use, the electrical heating element 13 heats water 25 within the chamber to boiling point so that steam is generated. A hose 27 is coupled to the upper end of the chamber 3 so as to provide means for transferring the steam to the desired location or hose attachment (not shown).

As the pressure of steam above the water in the chamber increases, the water level in the chamber will fall. The difference in level between the water level in the chamber and the tank will correspond to the pressure of steam. This will depend to some extent on the diameter of the hose 27. The diameter of the hose 27 is such that the pressure within the upper portion of the chamber 3 can lead to a pressure at an applicator or attachment, at the remote end of the hose 27, of for example 1. pound per square inch (above atmospheric pressure).

As can be seen from Figure la, the volume of water within the chamber 3 is less than the volume contained within the tank 1. This means that the heat-up time for the device is reduced considerably. In addition, in the event that the device is toppled over, very little spillage of boiling water 25 occurs. In this embodiment, the stored water 23 surrounds the boiling water contained within the chamber 3 thereby serving to insulate the boiling water from the user.

Some of the heat lost from the chamber 3 serves to heat storage water 23 thereby improving the heat-up time of the device.

As illustrated in Figure ic, the open topped tank 1 may be used to store the hose 27 when the device is not in use.

Figure 2 illustrates an alternative configuration of tank suitable for embodiments of the invention. In this embodiment, a tank 29 comprises a single opening 31 (in a cover 32) which acts as both an inlet for filling of the tank 29 and an outlet for passage of the steam generated within the chamber 3. The opening 31 is closable by means of a screw cap (not shown) when in use, the cap closes the opening 31 and steam generated within the cavity gives rise to an increased pressure in the space between the water and the cover 32. This pressure depends upon the diameter of the hose 27. The water: level in the chamber and tank will remain at the same level in this embodiment.

In this embodiment, the heating element 13 is provided with a bimetallic cut-out 33 which is operative for electrically disconnecting the heating element 13 in the event that its temperature exceeds a predetermined value.

The heating element 13 is positioned as low as possible within the chamber 3 so as to maximise the volume of water (within the chamber) which can be heated to generate the steam.

Figures 3a to 3c illustrate a further alternative embodiment of the invention. In this arrangement, a base 35 and a tank are of a modular construction and can be detached from one another. The tank 37 comprises a handle 39 at one end for enabling the device to be carried. At the other end, is provided a threaded opening 41 to which a correspondingly threaded screw cap 43 (see Figure 3c) is attached. The screw cap 43 comprises a nozzle 45 which penetrates through the base 35 and into the chamber 47.

The penetration of the nozzle 45 into the chamber 47 can be by means of a "push-fit" The tank 37 is made from a transparent plastics material and has a scale on the side as illustrated in Figure 3b. This scale serves to indicate the level of water contained therein.

The modular construction of the base 35 and tank 37 permits the coupling of tanks having different capacities for storing the water.

As illustrated in Figure 3c, the tank 37 can be filled by inverting the tank 37, removing the screw cap 43 and filling from a tap 17. After replacement of the screw cap 43, the tank 37 can be positioned onto the base 35 as illustrated in Figure 3a. This embodiment has the advantage that the tank 37 cannot be over filled.

When in use, the electrically heated element 13 is electrically coupled to a power supply by the wiring 11. Steam generated within the chamber 47 passes to the applicator (not shown) via the hose 27. An 0 ring seal 48 may be provided at the hose 27/chamber 47 outlet boundary.

A valve (not shown) can be fitted to the tank 37 for permitting the controlled entry of air into the tank 37. The entry of air serves to enable water to flow into the chamber 47, thereby providing for replacement of the water which has been turned to steam and discharged from the generator. Another valve (not shown) is preferably fitted between the chamber 47 and the entry to the hose 27 for controlling the rate Qf flow of water into the chamber 47.

In a modified arrangement of this embodiment, the nozzle 45 may be provided with a valve 49 for enabling opening or closure of the nozzle. The valve 49 may be coupled to a switch (not shown) for switching the heating element 13 on or off. As an alternative, a float (not shown) may be provided within the chamber 47, which float can close off the nozzle 45 when water within the chamber 47 reaches a given level. As steam is generated, the water level in the chamber 47 falls, so that the float also falls thereby opening the nozzle 45.

An attachment for use with the steam generating device described above is illustrated in Figures 4a to 4c. Figure 4a illustrates a conventional wallpaper stripping steam pad which comprises a steam inlet 51 which may be coupled to the hose 27. In Figure 4a, the steam pad 50 is acting against the under-side of a horizontal surface 53. Steam entering the steam pad 50 from the inlet Si is distributed over the area of the steam pad by means of a plate 55 having a plurality of openings 57 therein. During operation of the steam pad, steam condenses on the horizontal surface 53 and collects in the steam pad 50 as illustrated.

Figure 4c illustrates an embodiment of the present invention in which the steam pad is provided with a condensed steam outlet 59 for permitting the drainage of condensed steam (see arrow W). In this embodiment, the steam pad 50 is shaped so that condensed steam tends to drain towards the condensed steam outlet 59.

In the embodiment of Figure 4c, the steam inlet 51 is coaxial with the outlet 59. The steam inlet 51 and condensed steam outlet 59 are coupled to a hose 61 comprising a steam inlet pipe 63 which lies concentrically within the hose 61 thereby defining an annular channel 65 which provides for the drainage of condensed steam. The hose 61 can be coupled to the outlet 59 by means of a coupling ring 67.

The end of the hose 61 remote from the coupling ring 67 may be coupled to a corresponding concentrically arranged steam outlet positioned on the chamber 3 of the steam generating device. The annular channel 65 can be coupled to an input in the steam generating device which communicates with the tank 1. This will provide for return of condensed steam to the tank 1.

Figure 4d illustrates an alternative hose 69 comprising a pair of pipes 71 and 73 running parallel to one another. One end of the pipe 71 is coupled to the steam outlet of the chamber 3, the other end being connected to the steam inlet of the steam pad 50. One end of the pipe 73 is coupled to the tank 1 while the other is connected to the condensed steam outlet of the steam pad.

Figure 5 illustrates alternative arrangements of prop which can be used to support a steam pad against a wall or ceiling. In each of the three examples of Figure 5, a prop 75 is hingedly attached to the steam pad 77 at one end. Teach prop comprises a plurality of elongate segments which can be secured together by push fitting one end thereof into a female portion of the next segment (see enlarged section "A" in Figure 5).

Each prop 75 is provided with a supporting foot 79. The hose 27 may pass from the steam generator1 through the prop 75, and to the steam pad 77.

Figure 6 shows an exploded view of another steam generating device according to an embodiment of the present invention.

A trolley 80 is configured for receiving a tank 82 similar to the one described with reference to figure 2. A separate re-fill tank 83 is provided and fits snuggly within the fore end of the trolley 80.

A support 84 extends from the trolley 80 in order to assist securing of the tank 82 within the trolley.

Electrical connection between the heating element (see element 13 of Figure 2) is made via electrical connectors 85.

The ce-fill tank 83 has a volume which is about one quarter to one half of the volume of the main tank 82.

The purpose of the re-fill tank 83 is to facilitate easy transfer of water from a tap, which may be in a relatively inaccessible position, to the main tank 82.

The re-fill tank 83 is provided with a filler cap 86.

The re-fill tank 83 is also provided with an opening 87 into which condensed steam can drain.

This embodiment is provided with a detachable handle 88 which comprises a base portion 89 which comprises a threaded coupling 90.

The base 89 can be screwed to the handle 88 by means of screws 91. The handle and base 88, 89 can be engaged with a corresponding threaded portion 92 of the steam outlet of the tank 82. The thread may be such that full engagement may be established by a single 90 degree turn of the handle. A seal 93 is provided between the threaded coupling and the threaded portion 92 in order to effect sealing engagement therebetween.

The threaded coupling 90 is such as to engage with the inner pipe 94 so that steam from the generator can pass from the steam outlets 92 through the coupling 90 and into the inner pipe 94. Condensed steam passing within the annular passage (see for example reference numeral 95a of Figure 9) of the hose 95 passes inside the handle, through an opening 96 which is provided in the base 89 of the handle. Since the opening 96 lies over the opening 87 of the re-fill tank 83, when the handle is engaged with the main tank 82, condensed steam can flow directly into the re-fill tank.

Figure 7 shows an alternative embodiment of steam generating device which includes many features in common with the embodiment of Figure 6. Like reference numerals ace intended to designate similar features.

A projection 97a is provided on the top of the main tank 82 which engages with a downwardly extending projection 97b provided in the base 89 of the handle 88. The projection 97a engages with the projection 97b when the handle 88 is engaged with the main tank 82 in order to prevent over-tightening therebetween.

This embodiment comprises a level gauge 98 for indicating the quantity of water remaining within the tank 82. This gauge 98 is illustrated in more detail in Figure 11.

Slits 125 are provided in the side of the tank 89.

Behind the slits 125 there is a buzzer (not shown) for emitting a sound signal when the heating element has cut-out thereby indicating the need to re-fill the tank.

A power-on light 126 is provided on the side of the steam generator.

A tie 127 (partially illustrated) is provided in the generator for tying the hose when not in use.

In this embodiment, the handle 88 engages with the steam outlet 92 by means of a bayonet type coupling.

Figure 9 shows a detailed sectional view of the handle 88 of this embodiment. In this embodiment, the handle 88 is moulded into two pieces 88a and 88b. The portion 88b is fixed onto the portion 88a and is for directing condensed steam draining from the annular passage 95a into the re-fill tank 83. The inner pipe 94 is connected to a nozzle 99 of the threaded coupling 90. As can be seen from Figure 9, steam rising in the direction of arrow A from the tank 82 passes through the coupling 90 and into the inner hose 94 via the nozzle 99. An 0 ring seal 100 is positioned in the threaded portion of the steam outlet 92 in order to provide an effective seal.

The threaded coupling 90 is provided with a pressure release valve 101 which consists of a ball 102 which shuts off a vent 103 against the action of a helical spring 104. When the steam pressure within the tank 82 exceeds a level determined by the resilience of the spring 1.04, the ball 102 will be forced upwardly within the release valve 101 in order to permit the escape of steam.

This embodiment is provided with a mechanical lock 106. The lock 106 comprises a leg 107 which engages with the projection 97a of the tank 82. A resilient arm 108 extends from the top of the leg 107 and rests against the portion of the handle 88. The resilence of this arm 108 serves to maintain the mechanical lock in a closed position.

When it is desired to disengage the handle 88 from the tank 82 in order to fill the tank, then the button 109 of the lock 106 is pressed which causes the leg 107 to pivot about a pivotal point 110, the bottom end of the leg moving away from the projection 96 in the direction of arrow B.

Figure 10 is a section view taken along the lines B-B of Figure 7. This view illustrates the heating element 111 of this embodiment. Terminals 112 positioned beneath the element provide for the electrical connection of the element to a power supply.

A thermal cut-out device 113 is provided at the upper end of the heating element 111 in order to switch off the device when a predetermined temperature is reached.

Figure 10 also shows a boundary wall 114 (corresponding to the wall 3 of the embodiment of Figure 2) separating a heating chamber 115 from the storage portion 116 of the tank 82.

Figure 11 is a sectional view showing a detail of the level indicator 97. One end of a right angled tubular member 11.7 is sealingly passed through the side wall of the tank 82. To the other end of the member 117 a transparent cylindrical tube 118 is attached. The tube 118 contains a ball which rises and falls with the level of the water within the tank 82.

Figure 12 illustrates an alternative form of steam nozzle which may be used in conjunction with embodiments of the present invention. A hose 95 is attached to one end of the nozzle, the other end being in the form of an elongate slit 119. This nozzle enables relatively confined corners to be exposed to the steam generated by the device.

Figure 13 illustrates a further configuration of tank and chamber embodying the present invention. In this embodiment, a tank comprises a housing 201 which is closed by a base 202 sealingly attached to an open edge 203 of the housing 201 by means of a seal 204. Before closure of the housing 201, a chamber wall 205 is positioned within the tank and houses a heating element 206 which can be electrically connected to a power supply via a plug 207 sealingly fitted within an opening provided in the chamber wall 205 and the housing 201.

The housing 201 is provided with an opening 208 for enabling filling of the housing 201 and for enabling escape of steam generated by the heating element 206.

The chamber wall 205 is sealingly connected to the base 202 by means of a seal 209.

Means in the form of an opening 210 is provided in the chamber wall 205 at a position close to the base 202 for enabling the passage of water from the housing 201 to the chamber 205. The opening 210 is provided with an umbrella one-way valve 211 which is operative for permitting water to flow from the housing 201 to the chamber 205 but for preventing the reverse flow of water. This has the effect of eliminating the tendency of hot water to pass back into the housing 201 through the opening 210 by convection.

An insulation barrier 212 is provided on the surface of the water within the housing 201. The barrier 212, which may be in the form of an expanded closed cell foam or a blow moulded mattress of air1 or loose polystyrene balls serves to prevent steam making direct contact with the water within the housing 201 and condensing as a result. The presence of the barrier 212 thereby helps to maintain a satisfactory steam pressure and output at the opening 208.

Figure 14 illustrates a further embodiment of steam generating apparatus according to the present invention which embodies the form of tank and heating chamber described with reference to Figure 13. The embodiment of Figure 14 has generally the same functional characteristics as the embodiment described with reference to Figures 6 and 9.

The embodiment of Figure 14 comprises a trolley 215 for receiving the tank and a separate re-fill tank 216.

Electrical connection between the heating element 206 and a power source is made by means of a cable 217 which is coupled to the plug 207.

This embodiment is provided with a hose 218 having an inner pipe (not shown) for carrying steam from the generator to a steam pad 219. Condensed steam can pass from the steam pad 219 through an outer annular passage (not shown) of the hose 218. The condensed steam passes from the annular passage and into the re-fill tank by a mechanism similar in principal to the one described with reference to Figure 9.

A "power-on" indicator 220 is provided on one side of the housing 201.

Details of the embodiment of Figure 14 are illustrated in Figure 15. The housing 201 has a recessed portion 221 for housing a cut-off mechanism which is operative for switching off the device when the level of water within the tank falls below a predetermined level. The cut-off device comprises a float 222 which is connected to a microswitch 223 via a pivotally mounted cut-out lever 224. The pivotally mounted cut-out lever 224 is secured to the housing by means of a securing washer 225 and a seal 226. When the tank is full, the float 222 is buoyed up and so the lever 224 is urged against the microswitch 223. The microswitch remains switched on when the float is buoyed up. The microswitch may be provided with a spring loaded switch having a greater bias force than the weight of the float. This enables the switch to turn off in the event that the device is accidentally tipped over.

The heating element 206 is sealingly secured within the opening provided in the housing 201 by a threaded securing ring 227 and O-ring seal 228.

An attachment is provided for directing condensed steam from the annular passage 229 to the re-fill tank 216. The arrangement is also configured for directing steam generated by the device to the inner pipe 230 of the hose 218.

Figure 16 shows an alternative form of tank and chamber which can be incorporated into the embodiment of Figures 14 and 15. In this embodiment, an elongate passageway, in the form of a serpentine tube 232, provides a passageway through which cold water can pass from the tank to the hot water chamber.

In alternative to the serpentine tube 232, the passageway may be established between the chamber wall 205 and the base 202 as illustrated in insert A of Figure 16. In this case, a portion of the edge 234 has an inverted 'U' profile which opens inwardly into the chamber (not illustrated) at one end, and opens outwardly into the tank at the other end (not illustrated). When the wall 205 and base 202 are in position1 the 'U' profile of the wall is closed by the base 202 to form the passageway.

The passageway enables the device to generate a more even flow of steam. The reason for this is as follows.

As the water in the heat chamber 205 is heated, the water expands. This expansion (without a one-way valve o passageway) would cause the heated water to flow into the cold reservoir where it cools down. When the water in the heat chamber reaches boiling point and gives off steam1 the water level in the heat chamber drops and water is drawn in through the bottom to equalise the water levels. Because the 'new' water is from the cold reservoir, it cools down the water in the heat chamber and it stops boiling. The cycle is then repeated until the water in the reservoir is quite hot. This increases the time taken to produce steam and reduces the insulation effect of the cold water ceservoir. It also gives rise to an uneven o irregular generation of steam.

The anti surge tube o passageway ensures that water expelled from the heat chamber during heat up passes into the passageway and so is not allowed to mix with the cold reservoir water. The expelled water therefore retains its heat. When the heat chamber produces steam the water level in the chamber drops and the expelled warm/hot water in the passageway is drawn back into the heat chamber. Because the water which comes in to replace the steam from the passageway is still relatively hot, the water in the heat chamber is not cooled down to the extent where steam generation ceases. Therefore, the device can continue to produce steam at a relatively even rate.

The diameter of the passageway needs to be small enough to prevent convection and long enough to prevent cold water entering the chamber when the steam stripper is building up steam. The passageway is an alternative to a one-way valve.

The passageway may, for example, have a length of about 380 mm and a diameter of about 8 mm.

Figure 17 illustrates possible application of the passageway to the embodiment of Figures 14 and 15 in greater detail. The open edge of the heat chamber 205 is provided with a double wall 240 which defines a channel 242 which extends along three sides of the chamber 205. The double wall 240 sealingly fits within a pair of recesses or raised channels 244 provided between three upstanding walls 246 formed on the base 202. When the double wall 240 is received by the recesses 244 as illustrated in the inset drawing of Figure 1.7 (which drawing is a section taken along the lines X-X of the chamber 205), a tube or passageway 242 is defined and runs along three sides of the chamber.

One end of this passageway 242 opens into the tank at opening 248.

Water stored within the tank can pass through the opening 248 in the direction of arrow A, along the passageway and into the chamber via an outlet opening 250 in the direction of arrow B. The opening 248 is provided in the outer wall of the double wall, and the outlet opening is provided in the inner wall thereof.

The water is preheated as it passes along the passageway in the direction illustrated by the arrows.

The passageway also serves to enable the device to generate a more even flow of steam as explained above.

A cap 249 for the tank will now be described in detail with reference to Figures 18a,b and l9a,b. This cap 249 can be incorporated into the embodiment of Figures 1.4 and lS. and is similar to the cap illustrated in Figure 15.

In Figure 18a, the tank 201 has a neck 251 which is provided with a flange 252 at its open end. The flange 252 has a pair of notches (not shown) provided at diametrically opposite sides for receiving projections 254 of the cap 249. The coupling between the projections 254 and the flange 252 is similar to that between the cap and radiator of a conventional water cooled motor car radiator. That is to say, the cap 249 can be removed from the neck 251 when the projections 254 are aligned with the corresponding notches in the flange 252. In the normal locked position1 the notches are 900 from the projections. In order to remove the cap, the cap must therefore be rotated through 90".

The neck 251 is cylindrical in shape and has a tapered shoulder portion 256 on its inner surface. The taper of the shoulder portion 256 is disposed at an angle with respect to the centre line C-C.

The construction of the cap 249 is illustrated in Figures 19a,b. The cap 249 comprises an inner valve body 258 which has a flange 260 at its open end, four openings 261 at its closed end 262 for connection to a hose,-and a pair of ball valves 264 at its closed end.

The inner valve body 258 fits within a cylindrical housing 266 provided on the cap as illustrated in Figure 18b and is secured therein by a screw 263. The open end 268 of the cylindrical housing 266 is angled with respect to the sides of the housing and a recess 270 is defined between the end 268 and the flange 260 of the valve body 258. An '0' ring 272 positioned within the groove 270 lies in the position illustrated in Figure 18a when the cap 249 is secured within the neck 251. In this position, the cap 249 is locked, the open end 268 is parallel to the tapered shoulder 256, and the '0' ring 272 acts as a seal between the inner walls of the neck and the open end 268 of the housing 266.

When the cap 249 is rotated through the 900 relative to the neck 251, the open end 268 moves out of parallel with the tapered shoulder 256 thereby opening a gap between the open end and the flange which is too wide to be sealed by the '0' ring 272. The gap initially opens slowly as the cap is rotated thereby permitting slow release of pressurised steam within the tank. The steam escapes along the sides of the housing 266 and is directed away from the handled part 274 of the cap 249 in the direction of arrow D.

Figures l9a and b illustrate pressure release valves which comprise a pair of compression springs 276 and ball bearings 278. Each of the ball bearings is received within a respective ball valve 264 and serves to block an opening 279 provided in the closed end 262 of the inner valve body 258. The end of the compression spring 276 not contacting one of the ball bearings 278 urges against the inner wall of the cap (not shown).

When the steam pressure within the housing exceeds the biasing pressure exerted on the ball bearings by the springs, the ball bearings are pushed away from the openings 279 thereby permitting escape of steam from within the tank.

The stiffness of the springs 276 can be chosen so that the openings are opened at an appropriate steam pressure. Fscaping steam can be vented to the outside via a small hole present in the front of the cap.

Claims (24)

1. A mobile o portable device for generating steam1 comprising a chamber associated with a heating element for heating water within the chamber in order to generate the steam1 a tank for storing water, and means for supplying water from the tank to the chamber, wherein the capacity of the chamber for heating the water is small relative to the capacity of the tank, thereby enabling a decrease in the heat-up time of the water in the chamber, and the chamber is'disposed adjacent to or within the tank.

2. A device according to claim 1, wherein the means for supplying water is provided with a one-way valve for eliminating convective flow of heated water from the chamber through the means to the tank.

3. A device according to claim 1, wherein the waster supply means comprises an elongate passageway along which water moving from the tank to the chamber can pass.

4. A device according to claim 3, wherein the elongate passageway is formed integrally between a portion of the boundary between the walls of the tank and chamber.

5. A device according to any one of the preceding claims comprising an insulating barrier capable of floating on the surface of the water within the storage tank for preventing or reducing the quantity of steam condensing on the surface of the water.

6. A device according to claim 5, wherein the insulating barrier is formed of expanded closed cell foam or a blow moulded mattress of air.

7. A device according to any one of the preceding claims wherein the chamber is positioned within the tank so that during operation of the device at least some of the heat loss from the chamber can be used to heat the water stored in the tank.

8. A device according to any one of the preceding claims1 wherein the heating element is in the form of an electrical element provided with a cut-out for electrically disconnecting the element when the temperature thereof exceeds a predetermined value.

9. A device according to any one of the preceding claims, wherein the chamber is disposed substantially centrally within the tank so that the cold water within the tank serves as an insulator to protect the user from direct contact with the chamber.

10. A device according to any one of the preceding claims comprising an indicator for indicating the level or quantity of liquid within the tank and/or the chamber.

11. A device according to any one of the preceding claims, wherein the tank and the chamber are of modular construction whereby the tank is detachable from the chamber, and the supply means is such as to enable coupling of tanks of different capacity to the chamber.

1.2. A device according to any one of the preceding claims comprising a removable cap provided on the tank for enabling refilling thereof, steam release means being provided for permitting a relatively slow and controlled release of steam from the tank during the early stages of removal of the cap but before detachment of the cap from the tank.

13. A device according to any one of the preceding claims comprising pressure release valves for releasing pressure from within the tank when the steam pressure therewithin exceeds a desired level.

14. A steam cleaning or wallpaper stripping apparatus comprising a device according to any one of the preceding claims.

15. A steam cleaning or wallpaper stripping apparatus according to claim 14 comprising a hose for coupling a steam outlet of the chamber to a steam pad or nozzle.

16. A steam pad for a wallpaper stripping apparatus, comprising an inlet for receiving steam, means for assisting distribution of steam over the pad, and an outlet for permitting drainage of condensed steam from the pad.

1.7. A steam pad according to claim 16 shaped so as to have a thin elongate nozzle for allowing access to restricted areas.

18. A steam pad according to claim 16 or claim l', wherein the outlet and the inlet are substantially coaxial, the inlet being disposed centrally with respect to the outlet.

19. A steam pad according to claim 16, claim 17 or claim 18, comprising a hose for coupling to the inlet of the steam pad for connection to a steam generator, the hose comprising an inner and an outer pipe, one disposed concentrically with respect to the other so that an annular passage is defined between the inner and outer pipes, one of the pipes acting as a return flow channel when connected to the steam drainage outlet

20. A steam pad according to claim 16 or claim 17 wherein the inlet and the outlet are adjacent to one another for coupling to respective hoses substantially parallel to one another.

21. A device according to any one of claims 1 to 15 comprising a steam pad according to any one of claims 16 to 20, wherein condensed steam can be returned to the tank of the device by means of the drainage outlet.

22. A device according to claim 21 wherein condensed steam is fed to a separate re-fill tank.

23. A mobile or portable device for generating steam substantially as hereinbefore described with reference to Figure 1, Figure 2, Figure 3, Figure 6, Figures 7 to 11, Figure 13, Figures 14 and 15, Figure 1.6, or Figures 1.4 and 15 as modified by any one of Figures 17, 18a,b or Figure 19a or 19b.

24. A steam pad for a wallpaper stripping apparatus substantially as hereinbefore described with reference to Figures 4a to 4d, Figure 5 or Figure 12 of the accompanying drawings.