GB2445785A

GB2445785A - Noise reduction in fluid heating vessel

Info

Publication number: GB2445785A
Application number: GB0625697A
Authority: GB
Inventors: Robert Mason
Original assignee: Morphy Richards Ltd; Morphy Richards NI Ltd
Current assignee: Morphy Richards Ltd; Morphy Richards NI Ltd
Priority date: 2006-12-21
Filing date: 2006-12-21
Publication date: 2008-07-23
Also published as: GB0625697D0

Abstract

A heating component for a domestic appliance, said heating component comprising a heating plate; and a heating element disposed underneath said heating plate, wherein said heating plate comprises a plurality of upright protrusions which form a plurality of peaks and troughs on an upper surface of said heating plate for contacting a fluid to be heated. The projections cause small bubbles formed at the surface of the heating plate to grow as they run upwards along the projections thereby reducing localised superheating of fluid and producing a lower pitched sound when they eventually burst. A number of different configurations of projecting elements are disclosed including spirals, pyramids, vanes, parallel ridges, concentric ridges and individual projections arranged in geometric arrays.

Description

Low Noise Heating Component

Field of the Invention

The present invention relates to heating components for fluid vessels, particularly, although not exclusively, for electrical kettles.

Background to the Invention

Conventional electrical kettles have concealed heating elements, such that within a kettle vessel, generally at the base of the vessel, there is provided a substantially flat heating plate which contacts with water to be heated. The flat plate comprises either a piece of aluminum or stainless steel in contact with the water, with a resistive heating element concealed and fixed underneath the plate, so that the heating element does not come into contact with the water.

A problem with the known flat heating plates is the excessive noise produced when the kettle is boiling. Noise occurs through a process of microcavitation on the flat metal plate. Very small bubbles form and continuously burst at the metal-water interface due in part to localised super heating on the heating plate.

For metal bodied kettles having a metal vessel wall, the noise effect is exaggerated, as the kettle body can resonate with the continuously popping bubbles.

Summary of the Invention

A novel design of heating component alleviates much of the excessive noise due to small bubbles bursting at the metal-fluid interface by providing a plurality of upright protrusions formed into a heating plate. These upright protrusions allow small bubbles forming on the surface of the plate to run upwards along the surface of the protrusion, away from the heating surface, and thereby reduce localised superheating of the fluid.

The bubbles thus formed are larger, and so when they burst the sound made is lower in pitch than the sound made by bubbles bursting on a flat plate, where the bubbles are physically smaller in size.

The lower pitch boiling noise results in a reduced noise level during water heating and boiling.

According to one aspect there is provided a heating component for a domestic appliance, said heating component comprising: a heating plate; and a heating element disposed underneath said heating plate, wherein said heating plate comprises one or a plurality of upright protrusions which form one or a plurality of peaks on an upper surface of said heating plate for contacting a fluid to be heated.

Other aspects of the invention are as set out in the claims herein, which are intended to form a part of the teaching of this specification.

Brief Description of the Drawings

For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which: Figure 1 illustrates schematically a prior art kettle heating plate having a substantially flat heating surface; Figure 2 illustrates schematically in perspective view from above, a first heating component according to a first specific embodiment of the present invention having a heating surface provided with a plurality of ridges; Figure 3 illustrates schematically in perspective view from one side and above the first heating component of figure 2; Figure 4 illustrates schematically in perspective view from underneath, the first heating component of figures 2 and 3; Figure 5 illustrates schematically in cut away view from one side, the first heating component as described in figures 2 to 4 herein; Figure 6 illustrates schematically in cut away view, a protrusion on the is surface of a heating plate, according to a second specific embodiment, illustrating bubble formation at the base and on the sides of the protrusion; Figure 7 illustrates schematically a second heating component according to a second specific embodiment, in which a plurality of upright protrusions are arranged in a square or rectangular grid arrangement, enclosing a plurality of concave recesses; Figure 8 illustrates schematically a third heating component according to a third specific embodiment, comprising a plurality of upright finger like protrusions; Figure 9 illustrates schematically a fourth heating component according to a fourth specific embodiment, in which there are provided a plurality of concentric rings and troughs, each ring and trough having a substantially rectangular cross section in a tangential direction; Figure 10 illustrates schematically a fifth heating component according to a fifth specific embodiment, in which a plurality of upright arcuate protrusions are arranged to form an inner, a middle and an outer ring around the centre of a heating plate, wherein the protrusions of the inner, middle and outer rings are confined within a plurality of segments extending radially from a centre of the heating plate; Figure 11 illustrates schematically a sixth heating component according to a sixth specific embodiment, in which a plurality of arcuate and/or straight protrusions are formed in a series of rings concentrically around the centre of a heating plate, wherein a greater number of protrusions are provided in an outer ring compared to a middle ring or an inner ring; Figure 12 illustrates schematically a seventh heating component according to a seventh specific embodiment, in which a heating plate is provided with an upstanding inclined spiral ridge protrusion which extends from an outer periphery of a circular heating plate, towards a substantially central position of the heating plate, wherein the height of the ridge varies between the outer peripheral position and the inner substantially central position: Figure 13 illustrates schematically in side view the seventh heating component as shown in figure 12; Figure 14 illustrates schematically a view from one side and above, an eighth heating component according to an eighth specific embodiment, in which there is provided a plurality of circular concentric upright protrusions forming a plurality of ridges, where the heights of the circular ridges increases successively towards the centre of the heating plate; Figure 15 illustrates schematically the eighth embodiment heating component as shown in figure 14, from side view; Figure 16 illustrates schematically a ninth heating component according to a ninth specific embodiment in which a plurality of annular concentric upright ridge protrusions form a plurality of rings on the upper surface of a heating plate, wherein an outer ring has a greater height than a middle ring, which in turn has a greater height than a central ring; Figure 17 illustrates schematically a perspective view from the side, the ninth heating component of figure 16 herein; Figure 18 illustrates schematically a tenth heating component, comprising an upper heating plate having a plurality of pyramid like protrusions for dissipation of gas bubbles from the heating plate; Figure 19 illustrates schematically the tenth heating component of figure 18 herein in view from one side; Figure 20 illustrates schematically an eleventh heating component according to an eleventh specific embodiment in which a plurality of substantially pyramid like projections are formed on the upper surface of a heating plate, and arranged in a spiral pattern between an outer perimeter of the heating plate and a central positron of the heating plate; Figure 21 illustrates schematically in view from one side the eleventh heating component of figure 20 herein; Figure 22 illustrates schematically a twelfth heating component according to a twelfth specific embodiment in which a plurality of radially extended vanes are provided on the upper surface of a heating plate, wherein the vanes are alternately inclined outwardly and inwardly towards the centre of the heating plate; Figure 23 illustrates schematically the twelfth heating component of figure 22 in view from one side; Figure 24 illustrates schematically a thirteenth heating component according to a thirteenth specific embodiment, in which a plurality of radially extending vane like ridges are provided on the upper surface of a heating plate for the purpose of dissipating gas bubbles formed on the heating surface, wherein the plurality of vanes are each inclined towards the centre of the heating plate; Figure 25 illustrates schematically the thirteenth heating component of figure 24, in view from one side; Figure 26 illustrates schematically a fourteenth heating component accord ing to a fourteenth specific embodiment, in which a plurality of flat elongate vane like protrusions are arranged radially around a centre position of a heating plate, in which the vanes have a substantially constant height along their length; and Figure 27 illustrates schematically the fourteenth heating component of figure 26 in view from one side.

Detailed Description

There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to

unnecessarily obscure the description.

Referring to figure 2 herein, there is illustrated schematically in perspective view from above, a first heating component according to a first specific embodiment herein. The heating component comprises a substantially circular heating plate 200 having an upper surface 201 which is formed into a plurality of protrusions in this case in the form of concentric circular ridges 202 -204; and an electrical resistive heating element, arranged directly underneath the plurality of ridges.

Each ridge is formed of the same material as the rest of the plate. In the best mode, either aluminum or steel is used for the plate material. The plate may be formed either by stamping, pressing, or casting, or any equivalent manufacturing process.

The heating component also comprises a back plate, which may be a concave bowl shape which can be sealed to the underside of the heating plate, and an electrically resistive heating element which may be sealed in the cavity between the underside of the heating plate and the back plate.

Figure 3 illustrates schematically in perspective view from one side and is above the first heating component of figure 2. There are shown a plurality of upright ridges formed in an upper surface of the heating plate, having smooth curved contours on which small gas bubbles may form, and run up the walls of the ridges until they are released from the upper portions of the ridges as the liquid is heated.

In, water is in contact with the upper heating plate, which is heated by conduction and convection of heat from the resistive electric heating element underneath the heating plate. Water in contact with the heating plate is heated, and forms gas bubble. The gas bubbles form preferentially on the protrusions and release from the heating plate from positions on the protrusions.

Figure 4 illustrates schematically in perspective view from underneath, the first heating component of figures 2 and 3. The heating component comprises an electrically resistive heating element placed directly underneath the heating plate and in thermal contact with the heating plate such that in use, as electrical power is applied to the heating element, the element warms up and heats the heating plate. Electrical connections to the element are provided underneath the plate, so that the surface of the plate in contact with the water is unobstructed by the heating element. The heating element is protected by a back plate, which sandwiches the heating element to the underside of the heating plate, the back plate being fixed to the heating plate by welding, glue, pressing or other suitable fixing method.

Referring to fig 5 herein, there is illustrated schematically in cut away side view, the first heating component 500 described herein above. A plurality of ridges 501 -506 are spaced apart from each other in concentric rings, so that the surface of the heating plate forms a plurality of co-axially arranged circular ridges, with a plurality of co-axially arranged circular troughs there between.

The heating element 507, may be a conventional electrically resistive heating element, positioned immediately underneath the upper heating plate 500, to ensure efficient heat transfer from the heating element to the upper plate.

The peak to peak distance between the ridges is determined empirically to give the effect of generating the least amount of audible noise, for a given power of heating element 507.

The coils of the heating element may be arranged to coincide directly under the ridges, so that the ridges are directly heated by the heating elements, but the flat trough portions between the ridges are relatively spaced apart from the heating element, promoting heating of the water primarily at the ridges, and relatively away from the troughs, subject to overall heating of the plate by conduction of heat through the material of the plate.

By positioning the heating element directly underneath the ridges, any bubble formation preferentially occurs at the ridges and therefore dissipates as larger bubbles, in preference to formation of bubbles at the troughs.

The relative width of the trough floor may be varied to give an optimally low noise emission under conditions of heating, with the exact width of the trough floors relatively to the width of the ridges, and relative to the height of the ridges being determined experimentally.

In a best mode herein, it has been found that the following dimensions give an improvement in noise emission over a prior art flat plate kettle element: Overall diameter of plate 120 mm -157.5mm Distance between adjacent peaks of ridges 15mm -17mm Diameter between opposite peaks of outer circular ridge 94mm -97mm Diameter between opposite peaks of middle concentric ridge 60mm -64mm Diameter between opposite peaks of inner circular ridge 33mm -37mm Width of ridge 3mm -5mm Height of ridge 8mm -12mm In the best mode herein, three concentric circular ridges are provided, however in other embodiments, the pattern of ridges is not restricted to a concentric circular arrangement, but arrangements of various other ridge lay outs maybeused.

Referring to figure 6 herein, there is illustrated schematically in cut away view, a single protrusion of the heating plate under conditions of water heating.

The plate is heated from underneath by the electrical heating element. At the metal-water interface, microscopic irregularities in the metal surface in contact with the water lead to localised super heating of the water, converting the water into gaseous form. At this stage, the water gas bubbles are small, typically less than 0.1 mm in their largest dimension. Because the surface of the plate is inclined, a bubble forming at the base of the protrusion travels upwards, kept at the surface of the plate by surface tension at the interface between the bubble and the plate, but urged upwardly due to the relatively lower density of the gaseous water, compared to the surrounding liquid water. As the bubble travels upwardly along the surface of the ridge, heating of water continues, which increases the volume of the gaseous bubble, as the liquid water becomes heated and converts to gaseous form. As the bubble travels up the side wall of the protrusion, the size of the bubble increases. At any point on the side of the protrusion, or near the top of the protrusion, the bubble can release from the surface, as the upward force due to the difference in density between the gaseous form and liquid form exceeds the forces due to surface tension, which retains the bubble to the side wall. However, the majority of bubbles will travel up the side wall increasing in size as they move.

As the bubbles which release from the surface of the plate are relatively increased in size compared to their original size at initial formation, in general, the average size of bubble being released from the heating plate is larger than the average size of bubble released compared to a prior art flat surface heating plate.

Since the average size of the bubbles are larger, the center frequency of noise which the release of the bubble from the plate generates is lower than for relatively smaller bubbles, because the noise emitted when the bubble releases from the surface of the heating plate is inversely proportional to the physical dimensions of the bubble, with larger bubbles emitting lower frequency noise than relatively smaller bubbles.

When each bubble releases from the surface of the plate, it constitutes a separate individual noise generation source, because the event of release of a bubble from the plate generates vibration within an audible frequency range.

Consequently, fewer relatively larger bubbles being released from the heating plate represents a lower number of noise generation sources compared to the relatively higher number of smaller bubbles released from the prior art flat heating plate.

Further, since the average size of bubble is larger, the number of bubbles being released from the surface of the plate is relatively smaller, for the same amount of heating, compared to a prior art fiat plate. The equivalent amount of heating produces roughly the equivalent amount of gas phase water for both the prior art, flat plate and the embodiments herein. Therefore, the noise emitted by the first heating plate described herein is characterised by a relatively lower median center of frequency of the noise spectrum emitted, and a relatively fewer number of individual noise emissions, compared with the prior art case.

Referring to Fig. 7 herein, there is illustrated schematically a second embodiment heating component 700 having a substantially rectangular grid of ridges, each ridge culminating at an upper end in a smooth radius curvature arc, having a plurality of substantially square recesses positioned between a substantially square or rectangular grid of ridges. In this arrangement, a relatively higher proportion of ridge length may cover the surface of the heating plate, compared to the concentric ring arrangement.

Referring to fig 8 herein, in yet a further embodiment, ridges may be replaced by a plurality of upstanding fingers or stacks, arranged in a grid pattern, or a circular concentric ring pattern. In this arrangement, a relative upright area of the upstanding portion may be increased relative to a ridge structure, depending on how closely together the upright protrusions are arranged.

Each upright finger like protrusion may be substantially cylindrical over a significant height of the protrusion, or may be substantially frusto-conical in shape, in either case culminating at an upper end in a substantially hemispherical cap region. In operation of the heating component, as the heating is heated by the heating element underneath, the heating plate warms up due to conduction and convection of heat from the electrical heating element. Small bubbles form at the base of the upright protrusion, around a perimeter of the base, and travel upwardly, increasing in size as they rise, until they are released from the side or near the top of the finger like protrusion.

Because the finger like protrusion is substantially cylindrical or frusto-conical in shape, the protrusion presents an active surface area which extends all around the protrusion, from the curved base of the protrusion, up to the tip of the protrusion.

Referring to figure 9 herein, there is illustrated schematically a fourth heating component according to a fourth specific embodiment, in which a plurality of circular ridges are arranged concentrically to form a heating element surface.

The ridges form a plurality of troughs there between so that there are a plurality of concentric ridges and troughs forming the upper surface of the heating plate. Each ridge has a substantially rectangular cross section in a direction tangential to said ridge; and a centrally positioned mesa in the form of a cylindrical pill shaped protrusion is positioned centrally to said plurality of circular is ridges and troughs.

An outer most circular ridge is of a relatively larger width in a radial direction, than each of the plurality of inner circular ridges.

The heating plate of the fourth heating component could alternatively be viewed as a flat upper surface, having a plurality of concentric circular troughs, the troughs spaced apart from each other by substantially equal intervals in a radial direction extending from a centre of the circular upper surface. The cross section of each trough in a direction tangential to the trough is of a "U" shape, and/or forms three sides of a substantially rectangular shape.

Referring to figure 10 herein, there is illustrated schematically a fifth heating component according to a fifth specific embodiment.

The fifth heating component comprises a heating plate 1000 having a plurality of upright protrusions. The plurality of upright protrusions are arranged in three circular rings spaced equidistantly apart. Each ring is formed of a plurality of upright arcuate ridges, the ridges spaced at regular intervals from each other in a direction radially outward of a centre point of the circular plate. The plurality of arcuate ridges are arranged with respect to each other, such that viewed from a point at the centre of the plate 1000 a clear passage between of protrusions in successive rings is viewable along a plurality of radial directions, with the ridges formed within a plurality of segments between the radial lines, such that in each segment, there is an inner ridge, and an outer ridge, with the length of the inner ridge being less than the length of the middle ridge, the length of the middle ridge being less than length of the outer ridge, and such that the inner, middle and outer ridges each lie within a same radial angle of each other within a segment, each segment being separated from its neighbouring segments by a clear line of passage along a pair of radial directions forming a segment when viewed from the centre of the plate.

Referring to fig 11, there is illustrated schematically a sixth heating component according to a sixth specific embodiment.

The sixth heating component comprises a heating plate in the form of a circular substantially planar upper heating surface, and a plurality of upstanding ridges formed on the upper heating surface, with the heating element disposed underneath the heating plate.

The plurality of ridges are arranged in three concentric rings spaced apart from each other equidistantly in a radial direction outwardly from the centre of the plate. In the sixth specific embodiment, the inner and central rings of upstanding ridges, each have eight upstanding ridge protrusions. The outer ring however has sixteen upstanding ridges. Each ridge may be either a straight linear ridge or may have a curvature so as to be arcuate. In the embodiment shown, the inner ring has a plurality of arcuate ridges, and the outer ring has a plurality of straight ridges, arranged in a circle. In each of the rings, inner, middle and outer, the plurality of ridges in that ring are spaced apart from each other at regular intervals.

Taking a line of sight from a central point of the heating plate, the plurality of ridges are seperated such that there is a clear line of sight along each of eight separate radial directions, forming eight segments on the upper surface of the heating component. For the inner and middle rings, the ridges are positioned within a same radial angle of each other in each segment, extending fully over that radial angle, such that there is one inner ridge and one middle ridge within each segment. However, for the outer ring, there are positioned two ridges per segment, such that the outer ring of ridges are divided by a plurality of spacings arranged along sixteen radii spanning out from the centre of the plate, the sixteen radii each subtending the same radial angle as each other.

Referring to figures 12 and 13 herein, there is illustrated schematically a seventh heating component according to a seventh specific embodiment. The sixth heating component comprises a heating plate 1200 having a substantially flat circular planar heating surface arising out of which is a single ridge 1201 which extends in a spiral from an outer position near an outer rim of the circular heating plate, to an inner position at or adjacent a centre point of the circular heating plate. The single spiral ridge is inclined in a vertical direction so that starting at the outside of the spiral nearer the outer edge of the circular heating plate 1200 and travelling along an upper peak of the ridge to the inner position at the centre of the heating plate, the spiral ridge gradually gains in height above the fiat plane of the heating plate 1200 as shown in side view in figure 13 herein As with the other embodiments, the heating plate 1200 is provided underneath with a heating element, and a backing plate. The spiral is formed such that as the spiral winds back on itself, the distance between the peaks of the spiral ridge in a radial direction emanating from the centre of the heating plate is such that the ridges form a plurality of equally spaced ridges from each other in a radial direction.

Referring to figures 14 and 15 herein, there is illustrated schematically an eighth heating component according to an eighth specific embodiment. The eighth heating component is substantially similar to the first heating component described herein before, except that the height of the circular ridges varies from outer to inner ridge, with the inner ridge being the tallest.

As shown in profile from one side in figure 15, the outer ring 1500 is approximately 60% of the height of the inner ring and the middle ring 1502 is approximately 80% of the height of the inner ring, so that the heights of the rings are approximately in the proportion 0.6:0.8:1.0 to each other, taking the ratios of outer ring: middle ring: inner ring. However, it would be appreciated by persons skilled in the art that the relative heights of the rings may be varied in relation to each other. In other specific embodiments, a ratio of outer to middle to inner ring height may be expressed in percentage terms of the height of the inner ring as follows: -inner ring 100% -middle ring 75% -85% -outer ring -55% -65% As with the first specific embodiment described herein, the circular ridges have a curved surface and curved lower portion and are equidistantly spaced apart from each other in a radial direction from the centre of the heating plate.

Referring to figure 16 and 17 herein, there is illustrated schematically in perspective view from above and from the side, an ninth heating component according to a ninth specific embodiment.

The eighth heating component is substantially similar to the first heating component described herein before, but with the difference that the height of the circular ridges varies from ridge to ridge.

The ninth heating component comprises a heating plate 1600 upon which are formed a plurality of upright protrusions in the form of circular ridges, the circular ridges being co-axially aligned with equal spacing intervals between the inner ring and the middle ring, and between the middle ring and the outer ring.

The inner ring has a lower height than the middle ring, and the middle ring has a tower height than the outer ring. The ratio of heights of the inner, middle and outer ring in variations of the eighth embodiment may be in the following ratios: L0 -outer ring 100% -middle ring -75% - 85% -inner ring -55% -65% As shown in side view in figure 17, the outer ring is higher than the middle and inner rings and therefore obscures the middle and inner rings in view from one side.

Referring to figures 18 and 19 herein, there is illustrated schematically a tenth heating component according to a tenth specific embodiment.

Figure 18 shows the tenth heating component in perspective view fromabove and one side, and figure 19 shows the tenth heating component in view from one side.

The tenth heating component comprises a heating plate 1800, an electrically resistive heating element, positioned underneath the heating plate, and a pressed backing component 1801 forming a base of the heating component, the heating element being positioned and sealed between the backing plate 1801 and the upper heating plate 1800. The heating plate upper surface 1800 is provided with a plurality of pyramid shaped protrusions arranged in rows and columns across the surface. Each pyramid comprises four triangular faces, which subtend an angle in the range 45 degrees to 60 degrees at the apex of the pyramid. In the embodiment shown, on a circular heating component having a diameter in the range 120 mm to 157.5 mm, there are provided a total of 69 individual pyramid protrusions. The plurality of pyramids are positioned such that each pyramid is centred at the intersection of a square grid of rows and columns so that the plurality of pyramids are arranged in a square grid pattern on the upper surface of the heating plate 1800.

Referring to figures 20 and 21 herein, there is illustrated schematically in perspective view from above and one side, and from side view an eleventh heating component according to an eleventh specific embodiment.

The eleventh heating component comprises an upper substantially flat circular heating plate 2000, a resistive electrical heating element positioned underneath the heating plate 2000, and a backing plate 2001 which encloses the resistive heating element and which is sealed to the heating plate 2000.

On the upper surface of the heating plate 2000, there is provided a plurality of square pyramids 2002, the plurality of square pyramids arranged in a pattern which follows a spiral extending from an outer position near an outer periphery of the circular heating plate, to a central position of the heating plate. In the embodiments shown, there are 47 individual pyramids arranged in a line along a path of the spiral. Each individual pyramid has a square base and four triangular sides. At the peak of the pyramid, the triangular sides form an angle in the range 40 degrees to 50 degrees. The plurality of pyramids formed on the upper surface of the heating plate 2000 form a basis for formation of gas bubbles, which travel up the sides of the pyramids, increasing in size as they travel, and which release from the heating plate at the peaks at the pyramids. A noise reduction in bubble release occurs compared with the prior art flat heating plate, due to increase in size of the bubbles compared to the microscopically formed bubbles which may be formed on a prior art flat horizontal heating plate.

Referring to figures 22 and 23 herein, there is illustrated schematically in perspective view from above and one side, and in side view, a twelfth heating component according to a twelfth specific embodiment.

The twelfth heating component comprises a heating plate 2200, a backing plate 2201 and an electrically resistive heating element, encapsulated between the backing plate 2201, and the heating plate 2200, positioned underneath the heating plate 2200 for heating the heating plate.

The heating plate 2200 is provided with a plurality of wedge shaped ridges 2202 spaced apart from each other and positioned radially extending from a central position of the circular heating plate 2200 towards an outer perimeter of the heating plate. The ridges are divided into two sets, firstly a set of a plurality of ridges which are positioned at an incline and which rise in a direction radially outward of the centre of the heating plate, and a second plurality of ridges which incline along their length in a direction radially inwardly towards the centre of the heating component.

The first set of ridges are positioned at 90 degrees to each other, such that the four ridges of the first set are positioned on a first cross having its centre at the centre of the circular heating plate. The second set of ridges are positioned at 90 degrees to each other along the lines of a second cross, wherein the first cross is angled at 45 degrees relative to the second cross, with the centre of each cross coinciding at the centre point of the circular heating component 2200. Each ridge has a lower end and an upper end, and traversing a line along an upper periphery of the ridge follows an incline on each ridge. Each ridge has a pair of substantially flat upright sides, and a curved transition at the point where the lower extremes of the sides meet the planar flat portion of the heating plate. At the centre of the heating plate, there is a substantially circular region containing the centre point of the heating plate, where the ridges are spaced apart from each other, and ends of the ridges form a circle concentric with the centre point of the heating plate, leaving a clear circular region at the centre of the plate where there are no ridges..

Referring to figures 24 and 25 herein, there is illustrated schematically a thirteenth heating component according to a thirteenth specific embodiment, in perspective view from above and one side, and in side view. The thirteenth heating component comprises a heating plate 2400, a backing plate 2401 and an electrically resistive heating element sandwiched between the backing plate 2401 and the heating plate 2400 for electrically heating the heating plate 2400.

The heating plate 2400 is provided with a plurality of radially extending vane ridges, each vane shaped ridge extending between an outer periphery of the heating component, and a central position of the heating component. The vanes are positioned along a plurality of radial lines which form a plurality of segments, each segment subtendirig an equal radial angle to each other segment. Each vane has a pair of parallel sides, and an upper curved or flat portion. The vanes are angled so as to rise in a direction from an outer periphery of the heating plate 2400 towards a centre point of the heating plate. At the centre of the heating plate, there is a substantially circular region, where the plurality of vanes do not encroach, so that the higher ends of the vanes are spaced apart from each other around the periphery of a virtual circle, concentric with and around the centre of the circular heating plate 2400.

Referring to figures 26 and 27 herein, there is illustrated schematically in perspective view from one side and above, and in view from one side a fourteenth heating component according to a fourteenth specific embodiment.

The fourteenth heating component comprises a substantially circular heating plate 2600, and a backing plate 2601, sealed to the underside of the heating plate 2600, and there between is provided in a cavity formed between the underside of the heating plate 2600 and the backing plate 2601, an electrically resistive heating element, for heating the heating plate 2600.

On the upper surface of the heating plate 2600 are formed plurality of upright protrusions in the form of a plurality of elongate straight ridges, each ridge extending in a direction radially from the centre of heating plate to an external periphery of the heating plate. In the embodiment shown, eight individual upright protrusions, which could be otherwise described as vanes, extend around the centre of the heating plate, radially outwards, and are positioned along the boundaries of a plurality of eight segments, each segment having an equal radial angle to each other segment. Each vane extends between a centre position and an outer periphery of the heating component, but does not extend all the way along that radius, but rather only along a portion of that radius, so that between a first end of each vane and a centre position of the heating plate there is a gap, and between a second end of each vane and an outer periphery of the heating component there is second gap. Each ridge has a pair of opposite sides, which may be inclined relative to each other, a first end which may be semi conical, a second end which may be semi conical and an upper portion which may be semi cylindrical, or substantially flat with curved edges. The height of each vane above the substantially flat plainer surface of the heating plate 2600 in the embodiment shown is constant, so that the ridges have a constant height along their length.

In other embodiments, ridges may be formed in other patterns, for example a plurality of parallel lines of ridges may be formed on a heating plate upper surface.

In yet another embodiment, a plurality of zig-zag shaped ridges may be arranged in parallel to each other across the heating plate.

In yet a further embodiment, the ridges may be formed into a plurality of curved lines, for example sinusoidal parallel lines.

Claims

Claims: 1. A heating component for a domestic appliance, said heating

component comprising: a heating plate; and a heating element disposed underneath said heating plate, wherein said heating plate comprises one or a plurality of upright protrusions which form one or a plurality of peaks on an upper surface of said heating plate for contacting a fluid to be heated.
2. The heating component as claimed in claim 1, wherein said one or a plurality of protrusions are arranged in a regular geometric pattern.
3. The heating component as claimed in claim 1 or 2, wherein each said upright protrusion comprises: at least one upright side wall; and a curved cap region, said side wall portion extending upwardly to meet said cap portion, there being a curved base portion at a lower end of said side wall portion where said protrusion meets a floor portion of said heating plate.
4. The heating component as claimed in any one of the preceding claims, wherein said plurality of protrusions comprise a plurality of concentric rings.
5. The heating component as claimed in claim 4, wherein said plurality of rings are each of a substantially same height as each other.
6. The heating component as claimed in claim 4, wherein said plurality of rings have different heights to each other.
7. The heating component as claimed in claim 4, comprising a set of concentric upstanding rings which stand above a floor portion of said heating plate, and in an inner said ring protrudes to a greater height above said floor compared to an outer said ring.
8. The heating component as claimed in claim 4, comprising a set of concentric upstanding rings which stand above a floor portion of said heating plate, and in an outer said ring protrudes to a greater height above said floor compared to an inner said ring.
9. The heating component as claimed in any one of the preceding claims, wherein said plurality of protrusions comprise a plurality of elongate ridges arranged substantially parallel to each other to form a set of ridges and troughs.
10. The heating component as claimed in any one of the preceding claims, wherein said plurality of protrusions comprise a plurality of curved ridges arranged side by side.
11. The heating component as claimed in any one of claims I to 3, wherein said one or a plurality of protrusions comprise: a plurality of concentric circular ridges, each said ridge having a substantially rectangular cross section in a direction tangential to said ridge: and a centrally positioned mesa in the form of a cylindrical pill shape, positioned centrally to said plurality of circular ridges.
12. The heating component as claimed in claim 11, comprising an outer ridge at a perimeter of said heating plate, said outer ridge having a greater thickness in a radial direction than a said concentric circular ridge.
13. The heating component as claimed in claim 1, wherein a plurality of said protrusions are arranged in a plurality of concentric rings around a central position of said heating plate, each said rings comprising a plurality of said upright protrusions.
14. The heating component as claimed in claim 13, wherein the protrusions of each of said plurality of rings are arranged to align with each other such that said protrusions align with each other within a plurality of segments dividing an upper surface of said heating plate.
15. The heating component as claimed in claim 14, wherein each said segment contains a single protrusion per each said ring.
16. The heating component as claimed in claim 14, wherein each said segment contains a single protrusion e nng for each of a first and second said ring, and contains a pair of protrusions of a third said ring.
17. The heating component as claimed in any one of claims 13 to 16, wherein said protrusions comprise arcuate upstanding ridges.
18. The heating component as claimed in any one of claims 13 to 16, in which said protrusions comprise at least one substantially straight elongate ridge.
19. The heating component as claimed in claim 1, wherein a said protrusion comprises an elongate ridge formed on an upper water contacting surface of said heating plate, and extending in a spiral path from an outer perimeter region of said heating plate to an inner region of said heating plate.
20. The heating component as claimed in claim 19, wherein said spiral protrusion increases in height above a substantially flat floor region of said plate, form one end of said spiral to another end of said spiral.
21. The heating component as claimed in claim 1, wherein said one or a plurality of protrusions comprise one or more upright pyramid shaped protrusions.
22. The heating component as claimed in claim 21 wherein said pyramids are four sided pyramids.
23. The heating component as claimed in claim 21 or 22, comprising a plurality of said pyramids, arranged at the intersections of a plurality of rows and columns.
24. The heating component as claimed in claim 21 or 22, wherein a plurality of pyramid protrusions are arranged in a spiral path.
25. The heating component as claimed in claim 1 or 2, wherein said one or a plurality of protrusions comprise at least one elongate vane like protrusion extending in a direction outwardly from a centre portion of the heating plate and towards a perimeter of said heating plate.
26. The heating component as claimed in claim 25, comprising a plurality of vane like protrusions extending towards a perimeter of said heating plate.
27. The heating component as claimed in claim I or 2, comprising a plurality of vane like elongate protrusions extending radially outwards from a centre position of said heating plate towards a perimeter of said heating plate, wherein an upper periphery of each said vane is inclined with respect to a substantially flat floor of said heating plate.
28. The heating component as claimed in claim 1 or 2, comprising a plurality of vane like elongate protrusions extending radially outwardly from a central position of said heating plate towards a perimeter of said heating plate, wherein first set of said vane like protrusions inclined in a direction away from said centre, and a second set of said vane like protrusions inclined in a direction towards said centre.
29. The heating component as claimed in claim 28, wherein said first and second sets of vanes like protrusions are arranged alternately interleaved with each other.
30. The heating component as claimed in claim 1 or 2, comprising a pluraJity of vane like elongate protrusions extending radially outwards form a is centre position of said heating plate towards a perimeter of said heating plate, wherein an upper periphery of each said vane is substantially parallel to a substantially flat floor of said heating plate.
31. The heating component as claimed in any one of the preceding claims, wherein said a plurality of protrusions have dimensions in the following ranges: height above a floor of said plate, in the range 8mm-lOmm; and width in the range 3mm-4mm.
32. The heating component as claimed in any one of the preceding claims, wherein said plate is formed of a metal selected from the set: aluminium; and stainless steel.
33. A heating component as claimed in claim 1 or 2, wherein said upright protrusions comprise a plurality of ridges arranged in a grid pattern, said ridges defining a plurality of recessed troughs there between.
34. The heating component as claimed in claims 1 or 2, wherein said plurality of upright protrusions comprise an array of upstanding finger like protrusions formed on an upper surface of said heating plate.
35. The heating component as claimed in claim 1 or 2, wherein each said upright protrusion comprises: a substantially cylindrical upright side wall portion; and an upper curved cap portion.
36. The heating component as claimed in any one of the preceding claims, in which a said one or more protrusions comprises an upwardly extending wall portion, and an upper cap portion, wherein a lower portion of said wall is joined with a floor of said heating plate by a smooth curve along which a gas bubble may traverse, from a position of formation on said floor, such that said gas bubble moves in a direction along a surface of said protrusion, upon heating of said protrusion by said heating element.