GB2417670A

GB2417670A - Liquid heating vessel partitioned to control temperature

Info

Publication number: GB2417670A
Application number: GB0517861A
Authority: GB
Inventors: Vincent Joseph Garvey
Original assignee: Strix Ltd
Current assignee: Strix Ltd
Priority date: 2004-09-01
Filing date: 2005-09-01
Publication date: 2006-03-08
Also published as: CN1742659A; GB0419387D0; GB0517861D0

Abstract

An electric liquid heating vessel 6 is adapted to heat liquid therein to a predetermined temperature below boiling. The apparatus comprises a discrete volume 30 therein at least partly partitioned from the rest of the interior so as to inhibit mixing between liquid in the discrete volume and liquid in the rest of the interior of the vessel during heating. Liquid in the volume 30 is cooler than that in the rest of the vessel, e.g. because the planar heating plate 8 does not extend beneath the volume 30. When liquid is poured out of spout 16, the cooler liquid from volume 30 is mixed with the hotter liquid which would otherwise have been too hot (e.g. for making instant coffee) due to the residual heating effect of the de-activated heating plate. Volume 30 may be defined by two full height wall portions 22 extending from the wall 12 of the vessel, the gap between which is filled by a further wall part 28 of much reduced height.

Description

24 1 7670 - 1 Temperature Control of Heated Liquids This invention relates

to appliances for heating S liquids, particularly those for heating liquids to a temperature below boiling point.

Liquid heating vessels which heat water to boiling for making beverages such as tea, coffee etc. are very well known in the art. However, it is known that for making some beverages such as instant coffee it is desirable not to heat the water to boiling but rather to heated to a lower temperature such as 80-85 C. This avoids a slight impairment to the flavour of the coffee which can be caused by scorching.

Accordingly, there have been several proposals for liquid heating vessels that are adapted to heat liquid only until it reaches a temperature of approximately 80 85O. One particularly simple and convenient example of this is disclosed in our earlier application GB-A 2372421 which shows a thermally sensitive control that may be used to interrupt power to a heater when a user determined temperature has been reached. However, there are numerous other ways in which heating to a temperature below boiling may be achieved e.g. electronically.

The Applicant has recognised that liquid heating vessels adapted to heat liquid to a predetermined temperature below boiling suffer from a common problem.

When the desired temperature is reached and power to the heater is therefore interrupted, the water or other liquid continues to be heated to some extent by the residual heat in the electric heater. Whilst for a vessel which is full of liquid, say of the order of 1.5 litres, the temperature rise may only be of the order of 2 or 3 C, if a very small quantity of water is being heated, say a cupful of the order of 250 millilitres, the temperature rise could be of the order of 15 C.

This would therefore negate almost all of the benefit of attempting to heat the water to a temperature below boiling. This dependence of the thermal overshoot on the volume of liquid that is being heated means that the problem cannot be addressed simply by offsetting the operating temperature of whatever thermal sensor is used to measure when the desired temperature has been reached.

It is an object of the present invention to overcome the aforementioned problem and when viewed from a first aspect there is provided an electric liquid heating vessel adapted to heat liquid therein to a predetermined temperature below boiling, the apparatus comprising a discrete volume therein at least partly IS partitioned from the rest of the interior so as to inhibit mixing between liquid in the discrete volume and liquid in the rest of the interior of the vessel during heating.

Thus it will be seen by those skilled in the art that in accordance with the invention a liquid heating apparatus has part of the liquid separated from the rest so that part of the liquid is inhibited from mixing and will therefore be heated to a lesser degree than the rest of the liquid. This cooler liquid may then be mixed with the rest of the liquid after heating has finished to counteract the effect of thermal overshoot caused by the thermal mass of the heater.

By judicious selection of an appropriate volume to be partitioned the rise in temperature may be substantially negated. It will of course be appreciated that this arrangement automatically accounts at least partially for the volume dependence of the temperature rise since there will be a similar but inverted dependence of the cooling effect of a fixed volume of liquid on the unheated liquid. In other words, where the heated volume of liquid is large the fixed volume of lesser heated liquid will have a relatively small cooling effect but, as indicated earlier, this is all that is required since the corresponding thermal overshoot is low. Similarly, where a small volume of liquid is heated the cooling effect of the fixed volume of liquid will be relatively high but again this is what is required to overcome the effect of the thermal overshoot. In fact, the optimum volume of liquid will be that which cools the main body of the liquid down by the same amount it is heated by the thermal inertia of the heater. This could be determined theoretically from the relative heat capacities, temperature differentials etc., although in practice it is more convenient to determine it empirically.

The partially-partitioned volume of liquid could be contained in one or more suitable formations in the base of the vessel such as a sump or a peripheral moat.

Although it is known to provide sumps and moats in the base of a liquid heating vessel, these have previously been provided in order to sense when water has boiled and thus have a thermal sensor associated with them to detect a rapid rise in temperature when the contents thereof mixes with the main body of liquid upon boiling.

It should be appreciated that the function of the partitioned volume in accordance with the invention is entirely different since it is intended that the partitioned liquid does not mix with the rest of the liquid until after heating. The volume of water in a sump or moat in accordance with the present invention is likely to be significantly greater than that in known sumps or moats which are provided for boiling detection.

The volume of liquid in boiling detection sumps and moats is likely to be insufficient to have an appreciable effect on the temperature of the rest of the liquid under normal use.

The partitioned volume could take any convenient form and could be provided anywhere in the vessel. For example, a trough, pouch or cup could be provided in the vessel, e.g. attached to one of the side walls, the base or a lid of the vessel.

In presently preferred embodiments the liquid is partitioned in an enclosure associated with a side wall of the vessel. Preferably the side wall of the vessel forms at least a wall of the enclosure. Preferably the enclosure comprises one or more walls attached to or formed integrally with the side wall of the vessel. In a particularly preferred set of embodiments, the enclosure comprises at least one wall which is mechanically attached to the rest of the enclosure.

This facilitates production and gives the possibility of providing one of the walls of the enclosure of differing height depending upon the particular construction of the vessel. This would therefore allow the volume of the enclosure to be altered as required.

Preferably the partitioned volume is arranged such that it is filled automatically when the rest of the vessel is filled with liquid. Preferably, the partitioned volume is arranged such that the liquid therein is mixed with the liquid in the rest of the vessel when liquid is taken from the vessel, e.g. by tipping to pour it out. This is preferably achieved by simple arrangement of the outlet of the partitioned volume, e. g. having an open top. However, it is envisaged that more complicated arrangements could be provided where mixing was allowable when a vessel was tipped such as a mechanically operated valve or door.

This could even be operated by the control unit or independently by a user. Such a mechanism could also be used to partition the liquid after filling.

The enclosure could be completely isolated from the rest of the liquid in the vessel. However, it is preferred for there to be some fluid communication between them such that mixing is inhibited rather than being completely prevented. For example, the enclosure may be provided within the rest of the liquid and not completely sealed or with one or more apertures provided between them. This allows for simple automatic filling of the enclosure when the rest of the vessel is filled whilst still preventing significant mixing between the volume of liquid therein and the rest of the liquid in the vessel.

Preferably, the base of the enclosure is defined by the base of the vessel. It is preferred in such arrangements that the part of the base of the vessel defining the base of the enclosure is an unheated part.

For example, where the heater is a sheathed heating element on the underside of the base, the enclosure may be provided in the region opposite the cold tails of the sheathed heating element.

IS Whilst all forms of heater will have an associated thermal mass and thus the invention may be used with any type of heater, in preferred embodiments the vessel comprises a sheathed heating element attached to or integral with the underside of a plate which forms at least part of the base of the vessel. Such heaters tend to have the largest thermal mass and therefore benefit the most from the present invention.

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 cut-away side view of a liquid heating vessel in accordance with an embodiment of the invention; and Fig. 2 is a cut-away plan view of the interior of the vessel of Fig. 1.

Turning to Fig. 1, there will be seen a liquid heating vessel 2 in the form of a cordless bullet-shaped jug of the type well-known in the art. At the bottom of the jug is a base skirt 4 which conceals the control unit and cordless power connector, both of which are omitted for clarity. The control unit could be the Applicant's U10 XT control which is described in GB-A 2372421. Alternatively any control arrangement which interrupts power to the heater at a temperature below boiling could be used. The cordless connector may be the Applicant's P72 360 degree cordless connector.

The interior of the vessel 6 is closed at the bottom thereof by a planar heating plate 8 which has a peripheral channel 10 Trippingly receiving a downwardly depending portion of the vessel wall 12 as is well known in accordance with the Applicant's Sure Seal element fixture system (described in more detail in WO 96/18331). A sheathed heating element 14 is brazed to the underside of the heating plate 10. This is approximately C-shaped with the electrical terminals (cold tails) at the front of the vessel.

The jug 2 also comprises and filling and pouring spout 16 at the front, a handle 18 at the rear and a top lid 20.

As may also be seen from both of the Figures, a pair of radially extending vertical walls 22 is provided protruding from the foremost section of the side wall 12 and extending from just above the base plate 8 to the top of the vessel. The outermost edges of the two vertical walls 22 are provided with extruded C-shaped clips 24 which receive corresponding beads 26 on the two edges of a further wall part 28. As will be seen in Fig. 1, the vertical extent of the wall part 28 is relatively short compared to the height of the vessel 2.

The side wall of the vessel, the vertical walls 22 and the wall part 28 between them define a volume 30 which is partitioned from the rest of the interior of the vessel 6.

In use, the vessel is filled with water via the spout 16 or the lid 20. This will result in water occupying the main part of the interior 6 and also the partitioned volume 30. If the spout 16 is used the partitioned volume 30 will tend to be filled first.

Since the additional walled part 28 is simply clipped into the vertical wall 22 and is not sealed against the base plate 8, there will not tend to be any differential after filling between the water level in the partitioned volume 30 and the interior of the vessel 6. The bottom S edge of the additional wall part may be made deliberately uneven e.g. curved of scalloped to ensure this and/or the vertical wall 22 may stop just short of the base plate 8.

Water in the main part of the vessel 6 will be heated by the heating element 14 once power is switched on. Because the partitioned volume 30 is over an unheated portion of the base 8 and because relatively little mixing takes place between the partitioned volume and the rest of the liquid in the vessel 6, the IS temperature of the water in the partitioned volume 30 will remain relatively close to room temperature. Once the bulk of the liquid in the vessel 6 has reached the predetermined temperature e.g. 80 C, the control (not shown) will interrupt power to the element. However, the thermal inertia of the element 14, base plate 8 and the heat diffusion plate also provided on the underside (not shown clearly) will continue to heat the water in the main vessel 6 to a higher temperature. This temperature will depend upon the volume of water in the main vessel and could be anywhere between 2-3 C if the vessel is full to of the order of 15 C if only a cupful of water (of the order of 250 ml) is in the vessel.

However, when the vessel is lifted by the handle 18 and tipped to pour the water through the spout 16, the relatively cool water in the partitioned volume 30 will mix with the rest of the water to bring its temperature down. By an appropriate choice of the position of the walls 22 and the dimensions of the wall part 28, the volume of water in the partitioned volume 30 may be chosen such that the cooling effect provided when this water is mixed with the rest of the water approximately compensates for the thermal overshoot from the element.

The water that is poured from the spout 16 will therefore be at the originally desired temperature - e.g. 80 for making coffee.

It will be apparent to those skilled in the art that the embodiment described above is just an example of the principles of the invention and there are many ways in which it may be modified within the scope of the invention. For example, the partitioned volume could be provided within a sump or moat or indeed an enclosure or other volume provided anywhere within the vessel. - 9 -

Claims

Claims: 1. An electric liquid heating vessel adapted to heat liquid

therein to a predetermined temperature below S boiling, the apparatus comprising a discrete volume therein at least partly partitioned from the rest of the interior so as to inhibit mixing between liquid in the discrete volume and liquid in the rest of the interior of the vessel during heating.
2. A vessel as claimed in claim 1 wherein said discrete volume comprises one or more suitable formations in the base of the vessel.
3. A vessel as claimed in claim 1 wherein said discrete volume comprises an enclosure associated with a side wall of the vessel.
4. A vessel as claimed in claim 3 wherein the side wall of the vessel forms at least a wall of the enclosure.
5. A vessel as claimed in claim 3 or 4 wherein the enclosure comprises one or more walls attached to or formed integrally with the side wall of the vessel.
6. A vessel as claimed in claim 3, 4 or S wherein the enclosure comprises at least one wall which is mechanically attached to the rest of the enclosure.
7. A vessel as claimed in any preceding claim wherein the partitioned volume is arranged such that it is filled automatically when the rest of the vessel is filled with liquid.
8. A vessel as claimed in any preceding claim wherein the partitioned volume is arranged such that the liquid - 10 therein is mixed with the liquid in the rest of the vessel when liquid is taken from the vessel.
9. A vessel as claimed in claim 8 wherein the partitioned volume has an open top.
10. A vessel as claimed in any preceding claim wherein there is a degree of fluid communication between them such that mixing is inhibited rather than being completely prevented.
11. A vessel as claimed in any preceding claim wherein the base of the partitioned volume is defined by the base of the vessel.
12. A vessel as claimed in claim 11 wherein the part of the base of the vessel defining the base of the partitioned volume is an unheated part.
13. A vessel as claimed in any preceding claim comprising a sheathed heating element attached to or integral with the underside of a plate which forms at least part of the base of the vessel.
14. An electric liquid heating vessel substantially as hereinbefore described with reference to the accompanying drawings.