STEAM GENERATOR

Abstract: The Steam Generator comprises a block (85) of heat conductive material in one face of which is formed a water chamber (95) for the reception of water to be turned into steam by heat from an electric heater located in the block. The one face has also formed in it, first and second elongate passages (96, 97) each leading from the water chamber (95) to an intermediate transfer area. From each intermediate transfer area extends a transfer path that connects the area to a different one of the steam exits. The steam generator (3) may be used in a hand-held wallpaper steamer used for stripping wallpaper or in a hand-held steamer for removing creases from fabrics.

Description: This invention relates to steam generators for use in a hard-held wallpaper steamer for use in stripping wallpaper and other coverings secured to a surface by heat and/or moisture softenable adhesives. Such steamers have been proposed before but they have not been entirely satisfactory. In one particular prior proposal, steam is fed to an open faced steam chamber from a steam generator with steam exits from which steam emerges into the steam chamber. Steam generators have also been used in garment steaming devices, for example the garment steaming device described and claimed in US Patent No. 3,811,208. This device comprises a soleplate having a cast-in sheathed heating element and a thermostat mounted on one side thereof to regulate the temperature, a plastic housing means overlying and co-extensive with said soleplate and enclosing said thermostat and the electrical connections to said heating element, said housing means including a water reservoir and forming an upright column extending upwardly from said soleplate, a handle connected at one end to the top of said column and extending horizontally with a free end disposed laterally of said column and soleplate, a power cord entering said iron at said free end of said handle and extending through said housing adjacent to said reservoir and connection to said thermostat and said element. For best results, the flow or steam from each of the steam exits should be the same but it has not been possible to ensure that. Accordingly, it is an object of the present invention to provide a steam generator in which the flow of steam to each steam exit of the generator is about the same. According to the present invention, a steam generator for use in a hand-held wallpaper stripper comprises a water chamber for receiving water to be vaporized, at least two elongate convoluted passages, each passage serving to transfer vapour from the water chamber to on intermediate distribution area, steam exits from the generator located in transfer passages leading from the intermediate distribution area, and an electric heater for heating the water chamber, the convoluted passages and the transfer passages, characterised in that each of the at least two elongate convoluted passages transfers vapour from the water chamber to one of the intermediate distribution areas, a first transfer passage with steam exits connects intermediate distribution areas, a second transfer passage with steam exits connects intermediate distribution areas and a majority of the steam exits are supplied along substantially equal lengths of the transfer passages. An embodiment of the invention will now be described in greater detail with reference to the accompanying drawings of which: Fig. 1 is a perspective view from the front, one side and above of the embodiment, Fig. 2 is a perspective view similar to that of Fig. 1 but with one part shown separated from the remainder of the embodiment, Fig. 3 is a schematic perspective view from one side with a part removed to reveal the position of certain internal components, Fig. 4 is a general assembly sectional view of the embodiment, Figs. 5 and 6 are, respectively, a view from above and a view from below of a further part of the housing of the embodiment, Figs. 7 and 8 are, respectively, a section on the lines XV and XVI of Fig. 5, Fig. 9 is an underneath view of another component of the embodiment, Fig. 10 is a plan view of the component of Fig. 9 with part removed, Figs. 11, 12 and 13 are, respectively, sections along the lines XIX, XX and XXI of Fig. 10, and Fig. 14 is a side view of a part of the component of Fig. 9. The embodiment now to be described is suitable for steaming wallpaper prior to stripping the paper with a conventional stripping knife. However, the embodiment may also be used when stripping other surface coverings secured to the surface by heat and/or moisture softenable adhesives. The embodiment comprises a hand-held steamer with an "on-board" water supply that is replenishable by a user as necessary. As can be seen from Figs. 1, 2 and 3, the embodiment includes a housing 1 contoured to accommodate a detachable water tank 2, a steam generator 3 and a base portion 4 with a peripheral wall 5, thereby forming a downwardly-open (as viewed in Figs. 1, 2 and 3) chamber 6, hereinafter referred to as a steam chamber. Water from water tank 2 is pumped into a water chamber in the steam generator by an electrically powered pump shown diagrammatically at 7. Energisation of pump 7 is controlled by an electric switch 8 operated by a rocker arm 9. Steam from the steam generator 3 leaves the latter via exit holes in its lower face and emerges into the steam chamber via connectors described below. The housing 1 includes a central portion 10 which extends away from the base portion 4 and has a forward projection 11 beneath which the water tank 2 is located on a flat part 12 of the housing 1. Extending rearwardly from the uppermost part of portion 10 is a handle 13 of generally cylindrical shape and which terminates in a flat end 14 of triangular shape and which is part of the housing 1 thereby forming a handle of a closed loop configuration. The cross-sectional size of the handle 13 in a plane transverse to its length is much smaller than that rear face of portion 10 from which the handle 13 extends. As can be seen, the upper surface (as seen in Figs. 1, 2 and 3) of projection 11 is contoured as at 15 to accommodate the rocker arm 9 that operates the switch 8. Located in the forward projection 11 of the housing 1 is a catch 16 for retaining the water tank 2 in the position in which it is shown in Fig. 1. As will be explained in more detail below, catch 16 can be actuated by a user to release the water tank 2 prior to detaching the tank from the housing. The catch 16 is so contoured that it is displaced by the tank 2 on initial movement of the latter into the position shown in Fig. 1. On final movement of the tank 2, the catch 16 automatically returns to a tank retaining position. The housing 1 has, on both sides, air holes 17 which allow air to circulate within it so limiting heat transfer from the steam generator 3 to the housing 1. The water tank 2 is of generally cubic form but is contoured to blend in with the contours of the housing 1 when in position thereon. The upper wall 21 of the water tank 2 has a filler hole 22 normally closed by a removable stopper 23. The upper wall 21 also has a rectangular recess 24 which co-operates with catch 16 to retain the water tank in position on the housing 1. The rear wall 25 is recessed as at 26 to accommodate a connector 27 forming part of a water inlet tube 28 inside the water tank 2 and described in more detail below. The connector 27 automatically engages with a short nozzle 29 of pump 7 in the portion 10 of the housing 1 as the water tank 2 reaches its fully home position on the housing. The nozzle 29 is the output nozzle of pump 7 as will be described in more detail. The output of pump 7 is joined by a connector tube 30 to an inlet 31 of the steam generator 3. The housing 1 is of clam shell construction and is formed by two clam shells 18 and 19 which abut along a vertical fore and aft plane through the middle of the steamer. The line is indicated at 20 in Figs. 1, 2 and 3. The clam shells 18, 19 are moulded from a suitable plastics material for example talc filled polypropylene and are contoured on one face - the inner face - to support the components mounted inside the housing formed when the clam shells are placed together. The clam shells 18, 19 are generally similar as regards their external faces, each providing one half of the following parts of the housing 1 - central portion 10, the forward projection 11, the flat part 12, the handle 13 and the flat end 14. The base portion 4 of the embodiment is shown in Figs. 5, 6 ,7 and 8 and is of generally rectangular form when seen in plan as in Figs. 5 and 6. The base portion 4 which is of a plastics material, for example a glass fibre reinforced thermosetting polyester, or a thermoplastic polyester which is preferably glass fibre reinforced, has the peripheral wall 5 whose external shape is contoured as at 63 to merge smoothly with the lower surface of the clam shells 18 and 19 when those parts are assembled together. The gutter 66 is of somewhat greater width at its open or lower face, as viewed in Figs. 7 and 8, across the left-hand edge of the base portion 4 as viewed in Fig. 5, than it is along the side and rear edges of the base portion. This can be observed by comparing the width of the gutter 66 at the left-hand end of Fig. 7 with the width at the right-hand end and with the equal widths at both ends of the base portion as shown in Fig. 8, and this is for aesthetic reasons. The interior contour of the gutter follows that of the wall 5 and the stepped portion 65 or the upturned edge of the floor 64. As can be seen from Figs. 7 and 8, the wall 5 extends downwardly beyond the lower face of the floor for a short distance to form side walls for the steam chamber 6, the lower ends of the walls being bevelled as shown. The extent of the extension is determined by the need to create a sufficient volume beneath the floor 64 to allow the steam emerging into the steam chamber to disperse evenly throughout the chamber whilst ensuring, at the same time, a concentration of steam that is effective to soften the wallpaper adhesive. In the steamer shown in the drawing, the extension is about 5 mm. The base portion has a floor 64 whose periphery is upturned and stepped as at 65 to mate with the step 46 on the clam shells. The upturn is spaced from the wall 5 to form a recess or gutter 66 round the inside of the wall 5. The formation of the recess or gutter 66 strengthens the base portion at its periphery and also serves to collect water as will be described below. The capacity of the gutter 66 is sufficient to retain the condensation that normally occurs during a period of use equal to one filling of the water tank 2. The volume of the condensation is not large because a substantial proportion of the total condensation produced is absorbed by the wallpaper. Another factor bearing on the capacity of the gutter is the extent to which the gutter deleteriously affects the dispersal of steam within the steam chamber and clearly this extent must be small. In the steamer shown in the drawings, the maximum depth of the gutter through its length is about 26 mm measured from the lower eage of the wall 5. The maximum width at the lower open end of the gutter is about 14 mm. That maximum occurs along the left-hand edge of the base portion as viewed in Fig. 7. Elsewhere the gutter width at its open end is about 10 mm. The face of floor 64, seen in Fig. 5 and referred to as the upper face, has a series of upstanding strengthening ribs of which rib 67 lies on the longitudinal centre line of the floor and extends almost the full length of the floor. The rib 67 bridges upstanding bosses 68 with stepped bores 69 and nozzles 70 with bores 71 that are of decreasing diameter in a downward direction towards floor 64. Short transverse ribs 72 extending from rib 67 strengthen the floor 64 as do further transverse ribs 73 interspersed with ribs 72 and extending towards rib 67 from the sides of the floor. Further apertured bosses 74 extend upwardly from the floor 64 in positions that correspond with the bosses 49 on the clam shells 18, 19. The bores of the bosses 74 are also stepped internally but this is not shown in the drawings. The bosses 74 are strengthened by short radially extending ribs 75. In addition to the nozzles 70, the floor 64 has further nozzles 76 located in the positions shown in Fig. 13 and which are identical with the nozzles 70. Areas 77 in the sides of the base portion 4 are bearing areas on which the edges of the clam shells locate when they are assembled to the base portion. The right-hand (as seen in Figs. 5 and 7) end has an upstand 78 strengthened on its inside face with short ribs 79. At the end of the upstand 78 are slightly raised portions 80. Upstand 78 locates in the extension 46A in the clam shells and provides an area for the reception of a rating plate as can be seen in Fig. 4. Air holes 81 in the front part of the wall 62 assist in ventilating the interior of the housing. The lower face of the base portion 4 is shown in Fig. 14, the lower end openings of the bosses 68, nozzles 70 and bosses 74 being correspondingly referenced. Areas in the lower face bounded by lines 82 are recessed slightly with respect to the remainder of the face, the nozzles 70 being located adjacent the inner ends of those areas in regions 83 which are recessed with respect to recesses 82. Raised areas 84 in the contour 63 provide weirs between adjacent sections of the gutter 66 that tend to restrain movement of condensate along the gutter. Located within the housing 1 above the floor 64 is the steam generator 7 and this is shown in more detail in Figs. 9 to 14. As can be seen from Fig. 9, the steam generator 3 is of generally rectangular form when viewed front above. The generator has a body 85 of a heat conductive metallic light alloy. Projecting from the ends of the body 85 are mounting ears 86 apertured to receive mounting screws (not shown). Cast integrally with the body 85 is an electric heating element 87 of the sheathed, resistance kind and shown in Fig. 14. The ends of the element are indicated at 88 and the path followed by the element is indicated in dotted lines 89 in Fig. 9. As can be seen, the element is looped at one end, the body 85 being locally increased in thickness at 90 to accommodate the loop and other parts of the length of the element. The upper (as seen in Fig. 10) face of the body 85 is channelled will be described below and has a central recess 91 that accommodates a thermally responsive element 92 in good thermal contact with the body 85. The upper face of the body 85 is covered by a cover plate 92A apertured at 93 to give access to the element 92 and at 94. The plate 92A is slightly recessed round the aperture 94. The cover plate 92A is secured to the body 85 in a manner described below. The channelling in the upper face of the body 85 is seen in Fig. 10. The face has a water receiving chamber 95 of circular form when seen in plan as in Fig. 10. The water chamber 95 is located beneath aperture 94 of plate 92A. From diametrically opposed positions on the chamber 95 extend elongate convoluted passages 96, 97 which are mirror images of each other. The passages 96, 97 terminate in intermediate distribution areas 98, 99 respectively. From the intermediate distribution areas 98, 99 extend further transfer passages of which two 100, 101 lie along the sides of the body 85 and pass to the right hand (as viewed in Fig. 10) side of the water chamber 95 where they join a common transverse passage 102. In the centre of the transverse passage 102 is a steam exit 103 and while other stern exits 104 are located in the vicinity of the junctions with the transverse passage 102 of the passages 100, 101. Also extending from the intermediate distribution areas 98, 99 are further passages 105, 106 which after merging at 107 diverge in opposite directions to join a transfer passage 108. In the centre of transfer passage 108 is a further stern exit 109 whilst other stern exits 110 are located in the vicinity of the junctions with the transfer passage 108 of the passages 105, 106. The distances from the intermediate distribution areas 98, 99 along the passages 100 and 101 to the steam exits 104 and along the passages 105, 106 to the steam exits 110 are substantially equal. The steam exits 103, 104, 109 and 110 are at the upper ends of respective nozzles 111 formed in the body 85, that project downwardly from the lower face of the body 85. The locations of the nozzles 111 correspond with those of the nozzles 70 and 76 of the floor 64 of the base portion 4. The looped end of the heating element 87 is located in the general area beneath water chamber 95 thereby ensuring a high heat input to this area sufficient to "flash" water entering the chamber into steam. The lengths and depths of the passages 96, 97, 100, 101, 102, 105, 106 and 108 are such as to provide surface area sufficient to ensure further heating, and therefore drying, of the steam exiting from water chamber 95. The physical mass of the body 85 is related to the electrical rating of the heating element 87 and is such that the latter is able quickly to bring the body 85 to a working temperature. The nozzles 111 provide a slight restriction on the flow of stern from the generator so that steam at the steam exits 103, 104, 109, 110 are at a pressure slightly above atmosphere. Forming the passages and chambers in the same face of the body 85 facilitates manufacture as does the configuration of passages. To use the appliance, tank 2 is filled with water via the hole 22 in the upper wall 21 of the tank 2 and the hole closed by the removable stopper 23. The tank 2 is next placed in position on the housing, care being taken to ensure that the projecting extension 29 of the pump 7 passes through the lip 142 and into the connector. As the tank 2 is placed in position, the upper wall 21 of the tank comes into contact with the bevelled face 160 of the projection 159 and displaces it by flexing the lower part of the wall 157. As the tank reaches its final position, projection 159 snaps into recess 24 to hold the tank 2 in position in the housing 1. The power lead is then connected to a source of power and the neon lamp glows indicating that element 87 is energised. The user allows a short time for the steam generator to reach a working temperature and then rocker arm 9 is actuated to its 'ON' position so operating switch 8 and energising the pump. The rounded contour of the extension 135 facilitates operation of the rocker 127 of the switch 8 as the rocker arm 9 pivots on the bosses 134. Energisation of coil 172 draws the core 170 upwardly against the action of spring 171. Diaphragm 174 is flexed upwardly and draws in water from the tank 2 via filter 147, connector tube 28, inlet 185 and duck bill valve 183. Coil 172 is then de-energised and spring 171 forces the core 170 downwardly so flexing diaphragm 174 downwardly and expelling water through duck bill valve 187 and outlet 191. Energisation and de-energisation of the coil occur at about 25 cycles per second and this gives a continuous flow of water whilst the pump is operating. Water is pumped via connector 30 into chamber 95 where it is flashed into steam by the heat of the body 85. The generated steam flows along elongate convoluted passages 96 and 97 to intermediate distribution areas 98, 99 and thence to the outlet nozzles 70 where it emerges into the steam chamber 6 and rapidly fills the latter. The elongate convoluted passages between the water chamber 95 and the nozzles 70 allow the steam to be dried so that by the time it exits from the nozzles, the moisture content is very low. At this stage, the base portion is placed against an area of wallpaper to be stripped, the edge of the peripheral wall 62 being pressed against the wallpaper. Steam confined in the chamber permeates through the wallpaper and rapidly softens the adhesive holding the wallpaper in position. The steamer is then moved to an adjoining area of wallpaper while the user scrapes off the wallpaper covering the area. It is not necessary to maintain the pump energised continuously, the user may return the rocker arm to its 'OFF' position during movement of the steamer from one area of wallpaper to another. The water capacity of the tank 2 in conjunction with the rating of the heating element 85 and the pumping rate of pump 7 is such that the steamer can be used for about 20 minutes before the tank 2 needs refilling. The pumping rate is about 25cc/min. A water tank capacity of about 400 ccs in conjunction with a heating element rated at 1.2 kilowatts provides the time just referred to. The mass of the steam generated in conjunction with a heater of the rating mentioned vaporises water feed into chamber 95 and heats the vapour to a temperature of 120°C nominal measured in the chamber 6. Steam from the nozzles 70 enters the chamber at a pressure sufficiently high to ensure that the chamber 6 is quickly filled with steam and kept filled. This action is assisted by the recessed areas 82 and 83. The parameters just referred to allow the steamer to be of a size and weight that can be conveniently hand-held and used without excessive strain on the user. In addition, for an average wallpaper, the time that the user takes to strip an area that has just been steam treated is about equal to the time that the steamer takes to soften the adhesive in that area. The rating of the heater also means that the steamer is suitable for use in domestic premises. It will be appreciated that the bulk of the steam generator 3 is spaced from the floor 64 of the base portion 4. The ears 86 by which the generator is mounted upon the bosses 68 are thermally insulated by the parts 121 of the gasket seal/connector while the connectors 120 are interposed between the nozzles 111 of the steam generator and nozzles 70 and 76 in the floor 64 of the base portion. This ensures that the base portion which is accessible to a user always remains at a relatively low and safe temperature whilst it is in use. The steamer is normally used with the water tank 2 uppermost and in that position, it will be observed, for example from Fig. 4, that the steam generator 3 is located towards the lower end of the steam chamber 6 and that is a greater distance between the upper side of the steam chamber and the upper of the nozzles 70 and 76 than between the lower edge of the steam chamber and the lower of the nozzles 70 and 76. This siting of the generator relative to the steam chamber improves the distribution of steam in the chamber. The steamer can also be used in the removal of paper from ceilings. In that case, the chamber 6 is uppermost. Any condensation that forms on wallpaper during the steaming of an area of wallpaper on a ceiling tends to fall into the steam chamber where it collects in the gutter 66. The condensation may be discharged from the gutter 66 by simply returning the steamer to an upright position and allowing the condensation to run away.

Claims: A steam generator (3) for use in a hand-held wallpaper stripper comprising a water chamber (95) for receiving water to be vaporized, at least two elongate convoluted passages (96, 97), each passage (96, 97) serving to transfer vapour from the water chamber (95) to an intermediate distribution area (98, 99), steam exits (103, 104, 109, 110) from the generator (3) located in transfer passages (100, 101, 107, 108) leading from the intermediate distribution area (98, 99), and an electric heater (87) for heating the water chamber (95), the convoluted passages (96, 97) and the transfer passages (100, 101, 107, 108), characterized in that each of the at least two elongate convoluted passages (96, 97) transfers vapour from the water chamber (95) to one of the intermediate distribution areas (98, 99), a first transfer passage (100, 101) with steam exits (103, 104) connects intermediate distribution areas (98, 99), a second transfer passage (107, 108) with steam exits (109, 110) connects intermediate distribution areas (98, 99) and a majority of the steam exits (104, 110) are supplied along substantially equal lengths of the transfer passages. A steam generator as claimed in claim 1, characterised in that some of the steam exits (103, 104) are located towards one end of the steam generator and the remainder (109, 110) towards the other end of the steam generator. A steam generator as claimed in claim 2, characterised in that the water chamber (95) is located adjacent the steam exits (103, 104) towards the one end of the steam generator. A steam generator as claimed in claim 3, characterised in that the intermediate transfer areas (98, 99) are located adjacent the steam exits (109, 110) towards the other end of the steam generator. A steam generator as claimed in claim 4, characterised in that each of the convoluted elongate passages (96, 97) extends from the water chamber (95) along a different side of the steam generator. A steam generator as claimed in any of claims 1 to 5, characterised in that the water chamber (95), the elongate convoluted passages (96, 97) and each transfer passage (100, 101, 107, 108) are formed in a single block of heat conducting material. A steam generator as claimed in claim 6, characterized in that the water chamber (95), elongate convoluted passages (96, 97) and each transfer passage (100, 101, 107, 108) are formed in a planar surface of the block and in which the generator has a cover plate (92A) located over the water chamber (95), elongate convoluted passages (96, 97) and each transfer passage (100, 101, 107, 108). A steam generator as claimed in any of claims 1 to 7, characterised in that the electric heater (87) is a heating coil located in the block. A steam generator as claimed in any of claims 1 to 8 built into a hand-held wallpaper steamer for use in stripping wallpaper, which steamer comprises a housing with a base portion open at one face thereof to form a steam chamber with a peripheral wall.

Inventors: WILKINS, PETER RAVENSCROFT
Applicants: BLACK & DECKER INC.
Application year: 1987
Main classification: F22B1
IPC codes: D06F75, F22B1, B44C7