GB2339335A - Controls for electric water boiling vessels - Google Patents

Description

Cgntrols for Electric Water Boiling Vessels This invention relates to

controls for electric water boiling vessels and more particularly to such controls which interrupt or reduce the supply of electrical power to the heating means of the vessel in response to water in the vessel boiling i.e. boiling controls.

An example of such a boiling control is described in our International application WO 95/34187. In the control disclosed in this document, a bimetallic actuator is located beneath the lower end of a steam pipe, the upper end of which is open to the interior of the vessel. When the water in the vessel boils, steam is conducted by the steam pipe onto the bimetallic actuator, which when its temperature rises sufficiently operates to trip a lever which in turn opens a set of electrical contacts in the electrical supply to the vessel's heating element.

This arrangement works well although can suffer some drawbacks. One particular problem is sometimes caused when steam in the steam pipe condenses onto the inner surface of the pipe and then runs down onto the actuator. The condensed water has a tendency to accumulate on the actuator and so form a thermal barrier between steam and the actuator. It also increases the effective thermal capacity of the actuator by acting as a heat sink. Both of these effects tend to increase the amount of heat required to operate the actuator and therefore the time taken for it to switch off the electrical current once water in the vessel has boiled.

The present invention aims to alleviate the afore mentioned problems and from a first aspect provides a control for an electric water boiling vessel, comprising a steam sensitive actuator operable in the event of water in the vessel boiling, to reduce or interrupt the electrical supply to a heating element of the vessel, a connector for receiving the lower end of a steam pipe and comprising a receiving surface for receiving said lower end of the steam pipe, and a duct for admitting steam into said control, the duct comprising an upstanding wall spaced radially inwardly from said receiving surface such that in use condensation on the inner surface of said pipe may run down into a gap defined between the inner surface and the upstanding wall of the duct.

Thus it will be seen that in accordance with this aspect of the invention when a steam pipe is connected to the control, the duct will be inwardly spaced from the inner surface of the vapour pipe. Water condensing on the inside of the steam pipe will run down the inner surface of the pipe, but rather than running into the duct and thus potentially onto the steam sensitive actuator, it will run into the gap between the inner surface and the wall of the duct.

The receiving surface may be arranged to engage the inner or outer surface of the wall of the steam pipe. where the receiving surface is arranged to engage the outer surface of the steam pipe, it will be appreciated that the pipe should have a wall thickness less than the spacing between the receiving surface and the duct in order that a gap is maintained between the inner surface of the vapour pipe and the duct.

In the preferred embodiment, the receiving surface is provided on the outer face of a collar arranged around the base of the duct. In this embodiment, the receiving surface thus engages the inner surface of the steam pipe.

The receiving surface may comprise a plurality of discrete receiving portions - e.g. a plurality of circumferentially spaced pillars or ribs. Preferably, however, a continuous receiving surface is provided 3 which extends substantially around the duct.

The receiving surface may be sloping e.g. to make it suitable for holding a tapered end of a steam pipe. Preferably, however, for convenience and simplicity the receiving surface is substantially parallel to the duct.

Condensed water may simply be allowed in use to collect on a surface in the gap between the steam pipe and the duct and eventually evaporate. Preferably, however a drainage hole or holes is/are provided to allow the condensed water to drain away. For example where the receiving surface is provided on a collar around the base of the duct, the collar may be formed with a notch or the like to form a drainage hole.

The gap surface or upper surface of the collar, may be inclined towards the drainage hole(s) to encourage condensed water to drain away.

The steam sensitive actuator may be any suitable type - e.g. a shape memory metal. Preferably however the actuator comprises a bimetallic actuator, most preferably a snap-acting bimetal of a type well known in the art, for example as described in GB 1542252.

in accordance with the invention thus far described, at least in its preferred embodiments, the amount of condensed water entering the duct which could then collect on the steam sensitive actuator is significantly reduced. It is preferable however to reduce the potential amount of liquid on the actuator even further and in preferred embodiments the thermally sensitive actuator is laterally offset from underneath the duct. This means that if any water does enter the duct it will tend to drip out of the bottom without falling onto the actuator.

This is novel and advantageous in its own right, not just in the context of a duct having an upstanding wall and thus from a second aspect the invention provides a control for an electric water boiling vessel comprising a generally horizontally arranged thermally sensitive bimetallic actuator operable in the event of water in the vessel boiling to open a set of electrical contacts for interrupting or reducing the electrical current to a heating element, and an aperture'arranged to admit steam into the control, wherein said actuator is laterally offset from said aperture.

It will be appreciated that this invention represents a significant departure from the teaching in the art which has been that steam should be directed onto the thermally sensitive actuator. It was believed that this should be so to minimise the time taken for the thermally sensitive actuator to operate once water in the vessel has boiled. It has been found however that sufficient heat is available from steam diffusing laterally to operate the actuator and that any slight tendency for the operating time to be increased by this arrangement is outweighed by the benefit derived from a reduction of water collecting on the actuator.

The actuator may be only partially offset from the aperture, preferably however it is completely laterally offset - i.e. the actuator does not fall within the footprint of the aperture at all. Most preferably the actuator is laterally spaced from said footprint.

The aperture may simply be a hole in the control.

Preferably however a duct is provided, most preferably in conjunction with a connector in accordance with the first aspect of the invention, above such a hole.

In preferred embodiments a wall is provided at least part way around the aperture and actuator to reduce lateral dispersion of the steam and thus concentrate steam onto the actuator.

The advantage obtained by providing this wall may be enhanced by arranging for it in use to be in close proximity to or to touch a lower base cover, thereby forming a steam chamber when the control is mounted in a vessel and a base cover is placed over the control.

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view from above of a control in accordance with the invention; Fig. 2 is a perspective view of the control of Fig.

1 from below; Fig. 3 is an exploded view similar to Fig. 2; Fig. 4 is a perspective view from above of the control of Fig. 1 with the baseplate and bimetals removed and the lever arm exploded therefrom; Fig. 5 is a cross-section along the line A--A of Fig. 1.

Turning to the Figures, a control 1 is shown for an electric kettle or jug having a substantially planar heating element forming the base of the water receiving portion of the vessel. This control is substantially similar to, and functions in substantially the same manner, as the control described in our PCT publication No. W095/34187 and the Applicant's corresponding U18 control. Reference should be made to this document for a fuller understanding of its operation. Briefly, however as shown in Fig. 3, the control comprises a moulded plastics body 2, a lever arm 4 pivotally mounted on the body 2 and a metal baseplate G made of e.g. steel fixed to the body 2. The underside of the body moulding 2 includes one half of a so-called 3600 connector 8 such as the one described in our PCT publication No.

W095/08204 for supplying electrical power from a cordless base to the control regardless of their relative angular orientation.

As described in W095/34187, two bimetallic actuators 10 are mounted at the top of the control so as to be in good thermal contact with the heating element when the control is mounted thereto. In the event that the element overheats - e.g. due to the vessel being switched on with no water in it, one or both of the bimetals 10 will operate to open a set of electrical contacts (not shown) to cut of f the flow of current to the element and also trip the over-centre lever arm 4 to hold the contacts open.

At the other end of the control is a steam duct 14 which admits steam into the control, as is described in W095/34187. However in the embodiment of the present invention described herein, there is further provided around the base of the duct 14, an annular collar 16.

The radially outwardly facing surface 18 of this collar forms a receiving surface for receiving the inner surface 21 of a substantially cylindrical steam pipe 19.

It will be appreciated that when such a pipe is placed over the collar 16, the duct 14 will extend some way into the pipe but will be spaced from its inner wall 21 by an amount equal to the thickness of the collar 16. A notch 20 is provided in the collar which extends down into the body of the moulding 2 to provide a drainage hole. The plane of the top of the collar 30 slopes towards the notch 20 to aid drainage.

Referring to Figures 2 and 3, it will be seen that there is a further snap acting bimetallic actuator 22 of the type described in GE 1542252 mounted by four peripheral clips 24 which are an integral part of the body moulding 2. Unlike the control in W095/34187, the bimetallic actuator 22 is mounted so as to be laterally offset from the duct 14 as may be seen most clearly from Fig. 2. The actuator comprises a tongue 22a which is generally parallel to the axis of the control. The tongue 22a is aligned with a downwardly projecting nose 23 formed on the lever arm 4, an aperture 25 being formed in the body moulding to allow the two to touch.

It will be seen from a comparison of this arrangement and the U18 that the lateral offset and the orientation of the tongue 22a mean that the lever arm 4 is significantly shorter in the present embodiment. The actuator 22 and the area beneath the duct 14 are surrounded by a wall 26 which helps to reduce the lateral dispersion of steam entering the control through the duct 14 and thereby helps to concentrate it onto the bimetallic actuator 22. This is enhanced by arranging for the base cover of the vessel (not shown) to be in close proximity to or touching the lower edge of the wall. This will be seen to be the case in the present embodiment since the base cover will be approximately level with the lower edge 28 of the 3600 connector 8.

Notches 30 are provided in the wall 26 to allow steam and/or water to escape from the control.

In use the control 1 is clamped against a planar heating element forming the base of a water boiling vessel. A flexible steam pipe 19 is fitted over the collar 16 surrounding the steam duct 14. The other end of the steam pipe 19 is fitted near the upper part of the vessel so as to be in fluid communication with the water-receiving chamber through an aperture in the upper part of the wall of the chamber. A base cover is fitted over the underside of the control so as to contact the lower edge of the wall 26. A hole is provided in the cover to accommodate the cordless connector 8.

When water in the vessel boils, steam is generated, some of which will pass through the aforementioned aperture and thus enter the steam pipe 19. The steam is conducted by the steam pipe 19 through the duct 14 and into a chamber in the control formed by the base cover, the wall 26 and the moulded body 2 of the control. The steam disperses laterally within this chamber and thus impinges upon the bimetallic actuator. Once the actuator 22 has reached its operating temperature it reverse its curvature with a snap action, causing the tongue 22a to act on the nose 23 of the lever arm, thereby tripping it and switching off current to the heating element.

As steam is conducted downwardly by the steam pipe, some will condense on the inside surface of the pipe as this is of course at a lower temperature than the steam.

The resulting water tends to run down the inside surface of the pipe. However rather than then running into the duct 14, the water runs down into the gap between the inner surface of the pipe and the duct 14, collecting on the top surface 32 of the collar 16. The water will then drain through the notch 20 in the collar. Thus water is prevented from running down onto the bimetallic actuator 22 and affecting its operation by acting as a heat sink. It is possible that a small amount of condensation will get into the duct 14 or take place on the inside surface of the duct itself. However since the actuator 22 is laterally offset from below the duct 14, the water will drip onto the base cover without coming into contact with the actuator 22.

is It will be appreciated by those skilled in the art that only one possible embodiment of the present invention has been described and that many variations are possible within the scope of the invention. For example substantial benefits may still be obtained by providing an actuator offset from the steam entry aperture without forming a receiving surface offset from a duct as shown. Similarly the latter feature brings benefits even if the actuator is not offset. Furthermore the steam operated actuator need not be part of an integral control, but may be provided separately.

Claims (14)

Claims

1. A control for an electric water boiling vessel, comprising a steam sensitive actuator operable in the event of water in the vessel boiling, to reduce or interrupt the electrical supply to a heating element of the vessel, a connector for receiving the lower end of a steam pipe and comprising a receiving surface for receiving said lower end of the steam pipe, and a duct for admitting steam into said control, the duct comprising an upstanding wall spaced radially inwardly from said receiving surface such that in use condensation on the inner surface of said pipe may run down into a gap defined between the inner surface and the upstanding wall of the duct.-

2. A control as claimed in claim 1, wherein said receiving surface is arranged so as in use to engage the inner surface of a steam pipe.

3. A control as claimed in claim 1 or 2, wherein said receiving surface is substantially continuous and extends around said duct.

4. A control as claimed in claim 3, wherein said receiving surface is provided on a collar around said duct.

5. A control as claimed in any preceding claim, comprising a drainage hole to allow water to drain away from the control.

G. A control as claimed in claim 5 when dependent on claim 4 wherein said drainage hole comprises a notch in said collar.

7. A control as claimed in claim 6 wherein the upper surface of the collar is inclined towards the drainage hole to encourage condensed water on the upper surface to drain away. 5

8. A control as claimed in any preceding claim, wherein said steam sensitive actuator is laterally offset from said duct.

9. A control for an electric water boiling vessel comprising a generally horizontally arranged thermally sensitive bimetallic actuator operable in the event of water in the vessel boiling to open a set of electrical contacts for interrupting or reducing the electrical is current to a heating element, and an aperture arranged to admit steam into the control, wherein said actuator is laterally offset from said aperture.

10. A control as claimed in claim 8 or 9, wherein said actuator is completely laterally offset from said duct or aperture.

11. A control as claimed in claim 10, wherein said actuator is laterally spaced from the footprint of said duct or aperture.

12. A control as claimed in any of claims 8 to 11, comprising a downwardly extending wall around said actuator and said aperture or duct.

13. A control as claimed in any preceding claim, wherein said actuator is a snap-acting bimetallic actuator.

14. A control for an electric water boiling vessel substantially as hereinbefore described with reference to the accompanying drawings.