GB2300698A - Steam generator - Google Patents

Abstract

A steam generator has a base 1 in which an electrical heating element 2 is fitted for boiling water in the generator. The base and a lid 3 are welded together. The lid has an opening at which a filling spout 5 extends up. The spout is externally threaded for a filler cap 6. A non-return, flap valve 8 is provided at the opening. Normally, the flap valve is open, so that water can be poured in through the opening when the cap is removed and there is ambient pressure within the generator. If the cap is removed when there is an over-pressure of steam in the generator, the flow of steam up out of the opening closes the flap valve to prevent escape of steam.

Description

STEAM GENERATOR The present invention relates to a steam generator particularly, though not exclusively, for use in a wallpaper steamer.

Wallpaper steamers apply steam to wallpaper, to moisten it so that it can be readily removed from a wall for redecoration of the wall. A steamer, by its nature produces steam at 1000C and a pressure just above ambient pressure.

When the steam generator has boiled its fill of water, the water must be replenished for further use of the device.

Good practice of course involves switching off the electricity to the steamer's heating element and allowing it to cool before adding fresh water. However, impatience may result in the filler cap being removed from the generator before the element has cooled and even in extreme conditions before the pressure in the generator has dropped to ambient pressure. In this case, with residual water at the heating element still boiling, it is possible for steam and boiling water to spray from the filler cap opening when the cap is removed.

The object of this invention is to avoid this potentially dangerous occurrence.

According to the invention there is provided a steam generator comprising: a base including an electrical heating element, a lid sealed to the base, an opening in the lid and a filler cap for normally closing the opening, and a non-return valve at the opening arranged to allow water to be poured in through the opening when the cap is open and there is ambient pressure within the generator and to close the opening in the event of the cap being removed with pressure over ambient being present in the generator.

Preferably, the non-return valve is a flap valve.

Whilst the flap may be normally held against its seat, and moved down off its seat when water is poured into the generator; it is preferably normally spaced just below the seat to allow water to flow freely into the generator and able to lift bodily against its seat if required to operate.

Conveniently, the flap is centrally connected to the lid at a spider against which it closes.

In the preferred embodiments the flap is of flexible material and has a headed resilient stem which can be drawn through an aperture in the spider and recovers it shape with the head over the spider for supporting the flap. The operation of fitting the flap to the lid is performed before the lid is sealed to the base.

In the preferred embodiments, the caps are adapted to allow air into the steam generator in the event of a steam outlet from the generator becoming blocked, which can cause a partial vacuum in the generator when it cools. In one embodiment, the adaption is a non-return flap valve in the cap. In another embodiment, the cap is of the type used in on a car's radiator, which incorporates such a vacuum relief valve and a safety valve for the steam generator. In this embodiment, the cap and the non-return valve of the invention are arranged such that fitting of the cap inhibits the non-return valve, whereby the latter cannot interfere with the operation of the safety valve which is downstream of it.

To help understanding of the invention, two specific embodiments thereof will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a part-sectional side view of a steam generator of a first embodiment of the invention; Figure 2 is a similar view on a larger scale of the non-return valve in the steam generator; Figure 3 is a scrap plan view of the non-return valve and the cap opening at which it is provided; and Figure 4 is a view similar to Figure 2 of a second embodiment.

The steam generator shown in the drawings has a base 1 in which an electrical heating element 2 is fitted for boiling water in the generator. The base and a lid 3 are of plastics material. They are sealed together by welding.

The lid has an opening 4 at which a filling spout 5 extends up. The spout is externally threaded for a filler cap 6, which pressure tightly closes the opening in use. A steam outlet connector 7 is provided close to the foot of the spout for connection to a hose (not shown) leading the steam to a wall plate for use on wallpaper.

A non-return, flap valve 8 is provided at the opening.

It includes an EPDM moulding 9 of a flexible disc 10 with a central stem 11 carrying a head 12. During assembly, before welding of the lid to the base, the head is drawn through a central aperture 14 in a spider 15 arranged in the opening 4. The spider has three fingers 16 and a central boss 17 through which the valve stem 11 extends and above which the valve head 12 is supported. The fingers and the boss are integrally moulded with the rest of the lid.

Normally, the flap is suspended below the spider, so that water can be poured in through the opening when the cap is removed and there is ambient pressure within the generator. If the cap is removed when there is an over-pressure of steam in the generator, the flow of steam up out of the opening carries the flap against the spider.

The diameter of the flap is such that it closes the opening peripherally at a rim 18 extending slightly into the opening and to which the fingers radiate. In the event of the flap valve operating, once the generator has cooled down, equalising the pressure across the valve, the flap will drop down allowing more water to to be poured in.

The flap valve should never have to retain a high pressure, since the lid is provided with a safety valve 19.

The filler cap itself incorporates a non-return, elastomeric flap valve 20, which is arranged to prevent escape of steam in use. It comprises a disc 21 with a stem 22 drawn through the cap to hold a peripheral lip 23 of the disc in permanent contact with the underside of the cap.

Normally the disc holds pressure in the generator by being urged against the cap. Its purpose is to allow air into the the steam generator via an aperture 24 in the cap and depression of the disc; if, on cooling after use, air is unable to enter via the hose and connector 7, in which case the generator could collapse under the resultant partial vacuum in it.

Turning now to Figure 4, there is shown an alternative flap valve at an opening 104 in another steam generator.

The cap 106 fitted to the filling spout 105 of the opening 104 is of the type fitted to a car radiator. It includes a spring 150 urging a pressing 151 and a nitrile, elastomeric annulus 152 onto an annular face 153 incorporated in the top of the steam generator. Pressure on the underside of the pressing is resisted by the spring 150 until it reaches a value to overcome the spring and lift it. The steam within the steam generator can then escape into the spout 105 and out through a side aperture 154. This safety pressure release will not normally occur. Should a vacuum develop in the steam generator, a central smaller pressing 155, normally held up by a pin 156 and a second spring 157, will be drawn down from the nitrile annulus allowing ambient air into the steam generator.

Mounted below the cap is a flap valve 108 on a spider 115. The valve is similar to the valve 8 and the spider is similar to the spider 15. Thus if the cap is removed whilst the generator is pressurised, the flow of steam will draw the flap up against the spider, sealing the flow. Once the generator has cooled, the pressure dropped and the flap valve 108 has dropped down again, water can be poured in through the opening 104.

In order to prevent the flap valve 108 closing when the cap is in position, which would prevent the safety valve of the cap being pressurised and functioning, the spider 115 is set at a height below the annular face 153 such that the bottom of the pin 156 bears on the top of the stem 111 of the valve 108 to hold the valve in its open position. It will be appreciated that it is only when the cap is prematurely opened that the valve 108 need function.

Claims (10)

Claims:

1. A steam generator comprising: a base including an electrical heating element, a lid sealed to the base, an opening in the lid and a filler cap for normally closing the opening, and a non-return valve at the opening arranged to allow water to be poured in through the opening when the cap is open and there is ambient pressure within the generator and to close the opening in the event of the cap being removed with pressure over ambient being present in the generator.

2. A steam generator as claimed in claim 1, wherein the non-return valve is a flap valve.

3. A steam generator as claimed in claim 1 or claim 2, wherein the flap is normally held against its seat, and moved down off its seat when water is poured into the generator.

4. A steam generator as claimed in claim 1 or claim 2, wherein the flap is normally spaced just below the seat to allow water to flow freely into the generator and able to lift bodily against its seat if required to operate.

5. A steam generator as claimed in claim 4, wherein the flap is centrally connected to the lid at a spider against which it closes.

6. A steam generator as claimed in claim 5, wherein the flap is of flexible material and has a headed resilient stem which can be drawn through an aperture in the spider and recovers it shape with the head over the spider for supporting the flap.

7. A steam generator as claimed in any preceding claim, wherein the cap is adapted to allow air into the steam generator on its cooling in the event of a steam outlet from the generator becoming blocked.

8. A steam generator as claimed claim 7, wherein the adaption is a non-return flap valve in the cap.

9. A steam generator as claimed claim 7 as appendant to claim 6, wherein the cap is of the type used on a car's radiator, which incorporates the adaption and the safety valve for the steam generator, and the non-return valve of claim 1 arranged such that fitting of the cap inhibits the non-return valve, whereby the latter cannot interfere with the operation of the safety valve which is downstream of it.

10. A steam generator substantially as hereinbefore described with reference to Figures 1 to 3 or as varied in Figure 4 of the accompanying drawings.