GB2623292A - Kettle - Google Patents

Abstract

A kettle 1 has a spout 3 with a first cross section. A main body 2 of the kettle has a vent 10 having a second cross-section. The second cross-section (of the vent) is equal to or greater than the first cross-section (of the spout), to prevent boiling water being forced out of the spout. The kettle has an element assembly and a water chamber 5 that is closed by a lid 8. The vent may comprise a plurality of vent holes adjacent to the lid or on the side of the kettle body. There may be 8 to 10 vent holes. The kettle may be a swan neck kettle with a submerged spout.

Description

Kettle The invention relates to a kettle and in particular to a pour over or swan or goose neck kettle Over recent years, the demand for shorter heating times in kettles and jugs has led to an increase in the power of a typical heater from around 2.2KW to around 3.2KW. This is particularly so with the more widespread adoption of underfloor sheathed heating elements and thick film heaters. This power increase has been achieved without increasing the size of the heater so that the appliance does not need to be made larger to accommodate a larger heater. Thus the increase in heating power has led to an increase in the power density applied to the heater surface. This has, in turn, modified the process of heat transfer between the heater and water.

At low power densities, the difference in temperature between the heater surface and the water is quite low (typically 10 deg C) and heat transfer is achieved by convection. However, at the power densities typically seen in high power water 30 heaters (2080W/cm2), the difference in temperature between the water heater surface and the bulk liquid is increased significantly, and at a micro level results in the formation of bubbles of air or steam. This increased temperature difference modifies the process by which heat transfer occurs from a convective heat transfer process to a nucleate boiling process. These power density values give rise to bubble generation throughout the heating cycle.

Kettle element controllers are predominantly based on a mechanical bi-metal switches, activated by steam. There has been a recent trend to have electronic controlled kettles, where the elements are turned on and off by means of thermal sensors and electronic switches. Recently the pour over kettles have come to the market, which have submerged spouts and electronic temperature control. These are intended for use for specialty teas and filter coffees but can be used as a conventional kettle. The submerged spout provides precise pouring required for filter coffee. Pour over kettles tend to be lower powered than mainstream kettles, for example around 1100-1250W) and have a smaller volume (around 800 ml compared to 1.5 or 1.7 litres for a mainstream kettle).

In a mechanical kettle the heat of the steam passing down the steam tube is used to activate a bimetal switch in the base of the kettle. The bi-metal switch disconnects the live and / or the neutral supply, with a physical air gap between the contacts which results in an inherently safe design. This type of mechanical design is less susceptible to external supply power surges and spikes which may cause malfunction or the contacts to close. It can also be turned off by the user, either by resetting the switch or when the kettle is removed from the power base (called a lift off switch off). The element control is entirely mechanical, it is not turned on or off by electrical circuits or components.

However, in an electronic kettle, a thermal probe feeds back the temperature of the liquid in kettle (or the temperature of the kettle base plate) to a PCB. The power to the element is switched on and off by a relay or other similar device. As with all electrical systems, they are susceptible to malfunction A secondary thermal protective device is generally mandatory, in order to protect the product and user against malfunction in both electrically and mechanically controlled kettles, but will only activate once all the water has evaporated. The safety fuse is set above 100 °C so as to not activate during normal use. This is often referred to as boil dry protection.

During this period of water evaporation, the kettle is on a rolling boil and there could be situation where the steam pressure inside the kettle above the water line builds sufficiently to force water out the kettle spout if there is not sufficient steam ventilation. Potentially boiling water could then spurt from the spout.

In a mechanically controlled kettle there needs to be sufficient steam ventilation as the elements do not switch off immediately once reaching 100 degrees C. There is a period of time, up to 20 seconds, where the water can be boiling producing lots of steam.

With an electronic controlled kettle, in normal use there is unlikely to be an issue with steam pressure forcing water out the spout because the electronic control regulates the element power, switching off as soon as the water reaches boiling point reducing the creation of steam.

However in the event of a product malfunction of an electronically controlled kettle, where the primary element control has failed; the water may vigorously boil, generating lots of steam, which in turn may lead to water being forced from the spout In known swan neck kettles, at low fill levels, a rolling boil can build enough pressure so that water is forced out of the spout. It was found that this can occur at around 180m1.

The present invention therefore seeks to provide a kettle having a submerged or swan neck spout that improves the management of excess steam pressure, in particular in the event of an electronic control failure According to the invention there is provided a kettle having a main body with a water chamber, an element assembly and a spout, which spout has an opening into the water chamber at a height above the element assembly, the opening having a first cross sectional area, wherein the water chamber is closed by a lid, wherein the main body is provided with a vent having a second cross-section, the second cross-section being equal to or greater than the cross-section of the spout.

Preferably, the vent comprises a plurality of vent holes. Preferably, the vent holes are located adjacent to the lid. Preferably, the cross sectional area of the vent or sum of the cross sectional area of the vent holes is 30% greater that the first cross section of the spout, more preferably 40%. Preferably there are 8 to 10 vent holes.

In the invention the relationship between the cross-sectional area of the spout and the cross-sectional area of the steam vent hole is controlled and surprisingly and advantageously can eliminate boiling water being forced from the spout The increase of the cross-sectional area of the vent or the sum of the cross-sectional areas of the vent holes so that it is equal to or more preferably at least 30% greater than the cross sectional area of the spout at the entrance to kettle water chamber substantially eliminates water being forced out of the spout in the event of a PCB failure on an electronic pour over type kettle.

Fig. 1 shows a cross-section of a kettle Fig. 2 shows a top view of the kettle Figure 1 shows a cross-section of a swan neck kettle 1 having a main body assembly 2 with a spout 3 opening to the interior of the main body a short height above the heating plate 4, which divides the main body into a water chamber 5 and a chamber for the control electronics 6, which are shown schematically below the heating plate 4. An exemplary small volume of water 7 is shown, the upper surface of which is located just below the spout opening into the main body 2. The spout 3 has a swan neck form and an opening at a height at a level around the height of the main body.

In a typical exemplary embodiment, the kettle has a 1250W kettle elements, and 750m1 max fill volume. Preferably, the swan neck kettles has a submerged spout, with a cross sectional spout areas between 20mm2 and 176mm2 at the interface between the spout and the kettle body A preferred cross sectional area of the spout at the entrance to the main body is 50.2mm2. The cross-sectional area of the vent or the sum of the cross-sectional areas of the vent holes should be equal to or more preferably at least 30% greater than the cross sectional area of the spout at the entrance to kettle water chamber as this can substantially eliminate boiling water being forced out of the spout.

The main body 2 is closed by a lid 8 and is provided with a handle 9. Four vent holes 10 are shown at the top of the main body 2. Four further vent holes will be on the other part of the main kettle body. The cross sectional area of the vent holes in this example is 71.2mm2.

A baffle could be fitted to the inside of the kettle in the region of the vent holes to prevent boiling water from exiting the main body through the vent holes 10 either in normal use or in a failure mode Figure 2 shows a top view of the kettle showing the arrangement of the vent holes 10 at the top of the main body. The vent holes are arranged on the side of the kettle body with respect to a line between the handle and the spout. The vent holes should

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preferably be arranged in the sector shown between 600 from the line at the spout side and between 400, more preferably 600 from the line at the handle side. The vent holes 10 are arranged on both sides of the kettle. This arrangement of vent holes reduces the likelihood of water exiting the holes during vigorous pouring and of steam exiting the holes towards the handle when pouring.

Claims (1)

1. Claims A kettle having a main body with a water chamber, an element assembly and a spout, which spout has an opening into the water chamber at a height above the element assembly, the opening having a first cross sectional area, wherein the water chamber is closed by a lid, wherein the main body is provided with a vent having a second cross-section, the second cross-section being equal to or greater than the cross-section of the spout.A kettle according to Claim 1, wherein the vent comprises a plurality of vent holes.A kettle according to Claim 2, wherein the vent holes are located adjacent to the lid.A kettle according to any one of Claims 1 to 3, wherein the cross sectional area of the vent is 30% greater than the first cross section of the spout A kettle according to Claim 4, wherein the cross sectional area of the vent is in the range of 40% to 60% greater than the first cross section of the spout.A kettle according to any one of Claims 2 to 5, wherein there are 8 to 10 vent holes.A kettle according to any one of Claims 1 to 6, wherein the vent holes are arranged on the side of the kettle body.A kettle according to any one of Claims 1 to 7, wherein the vent holes are arranged with respect to a line between the handle and the spout between 60° from the line at the spout side and between 40°, more preferably 60° from the line at the handle side of the kettle.