GB2527939A

GB2527939A - Improved toaster

Info

Publication number: GB2527939A
Application number: GB1511635.3A
Authority: GB
Inventors: Ross Eaves; Glyn Hauser; Michael James; Grant Geeson
Original assignee: Morphy Richards Ltd; Morphy Richards NI Ltd
Current assignee: Morphy Richards Ltd; Morphy Richards NI Ltd
Priority date: 2014-07-01
Filing date: 2014-07-01
Publication date: 2016-01-06
Anticipated expiration: 2034-07-01
Also published as: GB2527780A; GB201411712D0; GB201511635D0; GB2527939B; GB2527780B

Abstract

A transparent toaster (100) comprises first and second upright heating plates 107, 108. Each heating plate 107, 108 comprises a glass substrate and a transparent thin film heating element 1500; 1501. Said thin film heating element 1500, 1501 has a film thickness which is relatively greater towards a lower region 1502, 1503 of said plate compared to a thickness of said heating element at an upper region 1504, 1505 of said plate. The film thickness may vary in a straight line linear manner between said lower region and said upper region or may vary as a series of discrete steps.

Description

Improved Toaster

Field of the Invention

[0001] The present invention relates to toasters.

Background of the Invention

[0002] Glass sided toasters have been suggested since at least 1946. US 2,564706 disclosed a toaster having a pair of heated glass plates forming a heating chamber of a toaster, where the heating plates were coated with a transparent electrically resistive heating element formed of antimony tin oxide (ATO) having 1% to 10% antimony Sb203 a tin oxide, and up to 20% of a further metal oxide having a metal selected from Copper CU, Zinc Zn, Thallium Th, Chromium Cr, Manganese Mn, Iron Fe, Cobalt Co or Nickel Ni.

[0003] In that disclosure although the glass heating plates with heating elements were transparent, a fully transparent see through toaster was not disclosed, Rather, an outer casing of an opaque metal material such as a metal protective shell was disclosed. Although the glass heating plates were transparent, the toaster itself was not see through.

[0004] The Philips® HD3001 toaster is an example of a known see through toaster design. A similar Philips® toaster is disclosed in USD 469,297.

The Philips® HD3001 has a heating chamber consisting of a pair of spaced apart glass plates, surrounded by a fully transparent outer shell. However the Philips® HD3001 does not appear to have been commercially successful.

[0005] An example of a commercially available known see-through transparent sided toaster is the known Magimix® Vision toaster, which has first and second transparent outer sides, each consisting of a pair of transparent glass plates, with a toasting chamber comprising a pair of glass plates being located between the sides. However, the Magimix® toaster uses long life quartz heating elements to provide heating of food items. The heating elements themselves are not transparent. A similar toaster is disclosed in USD599,607.

[0006] In international patent application W02010/131017A2 (PCT/GB 201 0/000993) of Morphy Richards, there is disclosed a see-through transparent sided toaster having first and second heated plates, each of which are coated with a thin film metal oxide semiconductor transparent semiconductor heating element, with transparent glass outer sides. In this arrangement, the heating plates are fully transparent both when in use, and when the heating elements are cold, and a user can see through the sides of the toaster [0007] It is an ongoing design objective to provide a fully see -through transparent toaster, which allows a user to view bread being toasted though the sidewalls or outer casing of the toaster, and which is suitable for domestic use, complying with all EU and equivalent safety regulations, and which gives performance equivalent or better than conventionally available opaque bodied toasters.

[0008] Problems which apply to transparent toasters include the following.

[0009] Firstly, there is the issue of cleaning the inside of the heating chamber. With a conventional opaque sided toaster, cleaning the inside of the heating chamber is not of primary importance, since the user cannot see inside the heating chamber from a position outside of the toaster, other than directly above. The visual appearance of the inside of the heating chamber is not especially important, but it is required that food debris can be removed so as to prevent burning within the heating chamber. However, with a transparent sided toaster any bread particles or other items sticking to the sides of the transparent plates or discolouring the transparent plates detracts from the overall visual aesthetics of the toaster, and therefore the ability to clean inside the heating chamber is more important.

[0010] The Philips® HD3001 glass toaster allows for removal of the whole outer casing, which can be lifted from the base to expose the heating chamber and allows cleaning inside. However, this exposes the internal heating elements to the user/consumer, and is therefore not ideal from the safety point of view.

[0011] The known Magimix® Vision transparent toaster solves the cleaning problem by having sides which are pivotally openable, allowing a user to manually clean the sides of the glass plates facing in towards the heating chamber. However, this has the potential problem that if the toaster has just been in use, the transparent plates may still be hot, and opening the side of the toaster may expose a user to a potential hazard of a hot glass plate.

[0012] A second problem which is particular to the use of a thin film semiconductor heating elements, for example antinomy tin oxide (ATO) heating elements, is that the bonding of metal electrical contacts to the ATO thin film is unreliable. This affects the durability of a glass heating plate toaster, and therefore its commercial viability as a consumer product.

[0013] A third problem is that of non-uniform heating within the heating chamber, with some pads of the heating chamber being hotter than others. If a thin film semiconductor heating element is applied uniformly to the glass heating plate, so that a substantially uniform power density is present across the surface area of the glass plate, because the glass plates are held upright or vertically, and because heat rises in air, the temperature at the lower part of the heating chamber adjacent the bottom of the plates will be lower than the temperature at the top of the heating chamber, adjacent the tops of the plates, leading to quicker browning of bread items at the top of the heating chamber, compared to the bottom.

[0014] Specific embodiments presented herein aim to address the above problems, and to provide an improved see through toaster.

Summary of the Invention

[0015] According to a first aspect there is provided a toaster comprising: first and second upright heating plates; each said heating plate comprising a glass substrate; each said heating plate comprising a transparent thin film heating element; wherein said thin film heating element has film thickness which is relatively greater towards a lower region of said plate compared to a thickness of said heating element at an upper region of said plate.

[0016] According to a second aspect there is provided a toaster comprising: a heating chamber for containing food items to be toasted; a food cage located in said toasting chamber for holding food items in said toasting chamber; said food cage comprising a base member capable of being raised or lowered; a drive motor and gearbox assembly for raising or lowering a said base member; and a connecting arm connecting an output shaft of said drive motor and gearbox assembly to said base member; wherein a first end of said connecting arm is connected to said drive motor, such that rotation of said drive motor causes a second end of said arm to raise or lower said base member; and wherein said first end of said connecting arm is connected to said drive motor at a position which is offset from a central plane bisecting said heating chamber.

[0017] According to a third aspect there is provided A toaster comprising: first and second heated plates, positioned opposite each other, and forming a chamber there between; each said heated plate comprising a transparent or translucent plate; :is each said heated plate having a transparent or translucent thin film heating element; an electrical power circuit for providing power to said thin film heating elements; a plurality of electrical contacts the connecting said electrical heating circuit to said thin film semiconductor heating elements; wherein at least one said electrical contact comprises a first electrically conducting part for touching against a part of a said thin film heating element, and thereby making electrical contact with said thin film heating element; and a resilient biasing means for urging said first electrically conducting part against said thin film heating element.

[0018] Other aspects are as set out in the claims herein.

Brief Description of the Drawings

[0019] 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 shows in perspective view from one end and one side, a toaster according to a specific embodiment disclosed herein; Figure 2 herein shows the toaster of figure 1 in view from a first side; Figure 3 herein shows the toaster of figure 1, in view from a second side; Figure 4 herein shows the toaster of figure 1 herein in view from above; Figure 5 herein shows schematically components of the heating chamber of the toaster of figure 1 herein, showing a bread cage assembly; Figure 6 herein shows schematically components of the heating chamber of the toaster of figure 1 herein, showing a bread cage raising and lowering mechanism with the bread cage floor in a raised position; Figure 7 herein shows schematically a position of a connecting arm of the raising/lowering mechanism, with the bread cage floor in a raised position; Figure 8 herein shows a motor and gearbox assembly, and a carriage member of the bread cage raising/lowering mechanism; Figure 9 herein shows the motor and gearbox assembly of the bread cage raising and lowering mechanism, having a connecting arm attached; Figure 10 herein shows schematically the bread cage raising/lowering mechanism with the bread cage floor in an intermediate position; Figure 11 herein shows schematically the connecting arm of the bread cage raising/lowering mechanism with the bread cage floor in an intermediate height position; Figure 12 herein shows schematically the bread cage raising/lowering mechanism with the bread cage floor in a lowered position; Figure 13 herein shows schematically the connecting arm of the raising/lowering mechanism with the bread cage floor in the lowered position; Figure 14 herein shows schematically the heating chamber, with part of the bread cage removed, allowing access for cleaning the heating plates; Figure 15 herein shows schematically the heating plates of the toaster, illustrating a variation in layer thickness of semiconductor oxide heating element; Figure 16 herein shows schematically mounting of the heating plates in the heating chamber, and an arrangement for electrical connections to the heating plate; Figure 17 herein shows schematically an arrangement of electrical contacts to the heating elements of the heating plates; and Figure 18 herein shows schematically operation of an electrical contact to a thin film heating element of a heating plate of the toaster.

Detailed Description of the Embodiments

[0020] 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.

[0021] Referring to Figure 1 herein, there is illustrated schematically a toaster according to a specific embodiment, in perspective view from one end and a first side.

[0022] As shown in figures ito 4 herein, a novel transparent sided toaster comprises a base 101; an outer casing 102; a first side 103; a second side 104; a first end 105; a second end 106; a first internal transparent plate 107; a second internal transparent plate 108; an electric motor 109; a bread cage assembly 110; said bread cage assembly comprising a first cage side and the second cage side, facing opposite each other, such that slice of toast or of the food to be heated or toasted can be inserted there between, and a cage floor, which is capable of being raised and lowered under power of the electric motor; a set of user controls comprising a start/stop control 111; a heating control 112, for selecting a browning level according to a visual display 113 on the first side of the toaster which is graduated in levels from 1.0 to 7.0; a defrost button 114; and a reheat button 115.

[0023] The first and second outer sides 103,104 comprise respective first and second outer glass plates 116, 117, which form the outside of the toaster, and which can be touched by the user. On the inside of the toaster, there is a heating chamber defined between the first and second internal transparent heated plates 107, 108. There is an air gap between the internal heated plates, and each of the outer transparent plates ii 6, ii 7, which prevents the user from touching the internal heated plates 107, 108 directly.

[0024] Between the internal transparent heated plates 107,i08 inside the heating chamber, there is provided the bread cage assembly 118. The bread cage assembly comprises a first upright grid 119, a second upright grid 120 and a cage floor 121 which is positioned between the first and second upright grids.

[0025] The first and second internal transparent plates 107, 108 are each provided with a corresponding respective transparent thin film semiconductor heating element, which is electrically operated to heat the transparent plates to cause browning of a bread slice or other item to be toasted, and which is placed in a toasting chamber between the heated plates. Since the first and second heated plates, the thin film semiconductor heating element, and the first and second sides 103, 104 are all transparent, this enables a user to see all the way through the toaster, and in use, watch bread or other food item being toasted.

[0026] Referring to figure 2 herein, looking at the toaster from the first side 103, a user can see all the way through the first outer transparent plate 116, the first internal heated plate, the second internal heated plate, and the second outer plate 117, these plate all being transparent.

[0027] The internal heating chamber has a floor; a first end; a second end; and sides provided by the first internal plate 107, and the second internal plate 108 which are spaced apart and face opposite each other forming a cavity therebetween in which the bread cage is located.

[0028] Referring to figure 3 herein, there is show the toaster in view from the other, second side. As with the view from the first side, the user can see all the way through the toaster in its unloaded state without any food items placed in the heating chamber. When food items are placed in the heating chamber, held by the bread cage, the user can see both sides of the food items, and watch them being heated up within the heating chamber.

[0029] Referring to figure 4 herein, there is illustrated the toaster in view from above, showing heating chamber and bread cage 117, comprising a first grid 118, second grid 119 and cage floor 120.

[0030] The grids are spaced apart from the internal transparent heating plates, there being a gap between each grid, and its adjacent respective internal heating plate, so that food item is placed between the grids are prevented from coming into contact with the transparent heating plates.

[0031] Each grid is located within the heating chamber by sliding the grid into opposing vertical slots or guides at a first end of the heating chamber 121, and a second end of the heating chamber 122.

[0032] The first and second grids are removable, by sliding them vertically upwards and out of the top of the heating chamber, thereby allowing access to the sides of the glass heating plates which face in towards the centre of the heating chamber, for cleaning. :is

[0033] Referring to figure 5 herein, there is illustrated schematically in perspective view, components of the bread cage, comprising first and second grids 118, 119; a bread cage floor 120; and first and second supporting frames 121 122 which support the first and second grids respectively.

[0034] Each frame 121, 122 comprises a lower horizontal member; and upper horizontal member; a first upright member at a first end of the frame, having a substantially "U" shaped channel facing inwardly towards the centre of the frame; a second upright member at a second end of the frame, having a substantially "U" shaped channel facing inwardly towards the centre of the frame.

[0035] In use, the first and second grids 118, 119 locate in the corresponding respective first and second frames 121, 122, but are removable from the frames by sliding the grids upwards out of the "U" shaped channels to allow cleaning of the inside of the heating chamber, and which also allows the grids to be taken out for the cleaning of the grids themselves.

[0036] Each grid 118, 119 comprises a substantially rectangular outer wire ring, having a plurality of vertical or upright wire bars extending across the outer wire ring. At the upper end of each grid there is provided one or a plurality of hooked over wire portions 123,124 which, in use rest upon the upper horizontal members of the adjacent supporting frames 121,122, so that the grids align in the vertical direction with the adjacent heated plates and supporting frames.

[0037] The upright ends of each grid locate in the corresponding respective upright slots/channels 125,126; 127,128 in the first and second ends of the supporting frames 121, 122, so that the grids slide vertically up and down in the upright channels of the frames, into and out of the heating chamber. The first grid further comprises one or a plurality of upright horizontal members 129, which provide convenient part of the grid which a user can grasp to manually lift the grid out of the heating chamber. The second grid similarly comprises one or a plurality of horizontal parts 130, for lifting the grid out of the second frame.

[0038] The bread cage floor 120 comprises a single elongate metal strip extending along a full-length of the heating chamber between the grids. The bread cage floor 120 has one or both ends attached to a corresponding respective up and down sliding carriage mechanism 131, one of which is located at the first end of the toaster, and the second one of which is located at the second end of the toaster. The floor of the bread cage is raised or lowered by sliding the ends of the floor member vertically up and down, under power of a motor and connecting arm which drives the first carriage 131 substantially vertically.

[0039] Referring to figure 6 herein, there is illustrated schematically in perspective view from the second end and above of the toaster, a raising and lowering mechanism for the bread cage floor. The raising and lowering mechanism comprises an electric motor and gearbox 600; and a connecting arm 601 which connects an output shaft of the gearbox to the bread cage floor 120 via the first carriage 131. The first carriage slides up and down in an upright track at a first end of the heating chamber.

[0040] A lower end 602 of the connecting arm is rigidly connected to a rotatable shaft 603. An upper end of the connecting arm is connected via an upper pivot point to a first sliding carriage 131 to which the floor 120 of the bread cage is attached. As the motor rotates, the gearbox rotates the shaft 603 in a circular motion, which rotates the connecting arm upwards/downwards, driving the carriage 131 upwards or downwards.

[0041] As the carriage moves up and down, a first side of the connecting arm 601 press a first switch 602 when in a "down "position, which sends a signal to stop the motor, and when the carriage moves to the "up" position, an opposite second side of the connecting arm presses against a second switch 603 which sends a signal to stop the motor.

[0042] In a lowered position, as shown in figure 6 herein, the lower pivot point 603 is in a lower most position, which draws the floor to a lowered position.

The bread cage floor is a lowered position, when the toaster is in a toasting state, with the heating plates activated, or when the toaster is in a cleaning mode, enabling access to the inside of the heating chamber but with the heating plates deactivated.

[0043] In the design of toasters, compactness is an ongoing design objective, both from the static point of view, and from the point of view storage of toasters in cupboards, and the amount of worktop space that toaster occupies. In particular, for a toaster having a toasting chamber for a single row of bread slices or other items to be toasted, the toaster can be made thinner than for double toaster having two rows of toast at the same time.

[0044] In the embodiment described herein, the position of the rotatable shaft 603 is offset relative to a vertical plane which bisects the bread cage floor 120, and/or a vertical plane which bisects the heating chamber, thereby allowing a longer arm than would be feasible if the centre of axis about which the arm pivots were to be located centrally relative to the heating chamber, for a given length of vertical movement.

[0045] Alternatively, for a given length of arm, the offset pivot point of the low end of the arm permits a more compact arrangement than would be available using an electric motor and gearbox where the output shaft is concentric with the armature of the motor.

[0046] Referring to figure 7 herein, there is illustrated schematically in view from a first end of the toaster, the raising and lowering mechanism, with the bread cage floor 20 in the upper position. As the motor rotates, the pivot point of the connecting arm 601 rotates until at a top dead centre position, as shown in figure 7, the bread cage floor 120 is at its raised or uppermost position. The floor is in this position, when the toaster is in the off' state, ready for use, or at the end of a cooking operation.

[0047] Referring to figure 8 herein, there is illustrated schematically in perspective view from the first end and one side, a rear side of the carriage 131 and motor/gearbox 600, showing the connecting arm 601 and carriage in a raised position. At a second end of the arm there is provided a roller bearing 800 which slides along a corresponding slot or track 801 in the rear of the carriage 131 between a first end and a second end of the slot, as the arm moves up and down. As the distal end of the arm 601 moves in a circular path, the rotatable bearing 800 either pushes up against an upper surface of the slot, or down against the lower surface of the slot, whilst the roller bearing moves along the slot 801 in the rear of the carriage, causing the carriage to move up or down in its upright track.

[0048] Referring to figure 9 herein, there is shown schematically the motor and gearbox assembly 600, connected to the connecting arm 601 with the connecting arm in an upright position. The motor comprises an outer casing 900 of a substantially circular cylindrical pill shape. Within the casing, a central armature of the motor is located substantially centrally on a main central axis of the outer casing. Within the casing, there is provided a set of gears which drive an output shaft 603 which rotates about rotational axis which is parallel to, but offset from the main central axis of the motor and therefore offset from the main central axis of the casing. In the upper position, a distal end of the connecting arm 601 is located at a first end of the slot in the carriage 131.

[0049] Referring to figure 10 herein, there is illustrated schematically in perspective view from above and the second end, components of the bread cage raising/lowering mechanism in an intermediate position with the bread cage floor lowered from its uppermost position.

[0050] Referring to figure 11 herein, there is illustrated schematically a position of the connecting arm 601 when the raising/lowering mechanism is in the intermediate position. The connecting arm 601 is substantially horizontal. As the first end of the arm is located at a pivot point which is offset relative to the centre of the heating chamber, this permits a relatively longer length of arm than would be possible if the lower end of the arm were centrally located. In this position, the roller bearing 800 is positioned at a second end of the slot in the carriage.

[0051] Referring to figure 12 herein, there is illustrated schematically in perspective view from above and the second end of the toaster, components of the bread cage assembly and drive mechanism, with the bread cage floor 120 in a fully lowered position. In the fully lowered position, the connecting arm 601 is positioned downwardly, so that the carriage 131 is positioned at a lower most part of its track and a lower most position.

[0052] Referring to figure 13 herein, there is shown schematically a position of the connecting arm 601 relative to a main central axis of the motor and gearbox assembly 600, with the bread cage in a lowered position, in which the distal end of the connecting arm and the roller bearing 800 is returned to the first end of the slot in the carriage 131.

[0053] When raising the carriage and the floor member from a lower most position to an uppermost position, the connecting arm rotates in a first rotational direction, causing a second end of said connecting arm to slide between a first end of said slot/track of said carriage, and to a second end of said slot/track of said carriage, and then to return to said first end of said slot/track of said carriage.

[0054] Similarly, when lowering the carriage from an uppermost position to a lower most position, the connecting arm rotates in a second and opposite rotational direction, causing a second end of said connecting arm to slide between a first end of said slot/track of said carriage, and to a second end of said slot/track of said carriage, and to return to said first end of said slot/track of said carriage.

[0055] In either case, the second end of the connecting arm describes a semi -circular path when traversing between a fully raised position and a fully lowered position.

Normal Toasting Operation [0056] The normal toasting operation, a user places a slice of bread, or other food item such as one or more half bagels into the heating chamber. The food items are located between the sides of the bread cage, and rest on the bread cage floor. When the heating elements are off", the bread cage floor is normally in the raised position. Turning the toaster to the "on" state by activating the start/stop control 111 causes the bread cage to be lowered by the electric motor, and the heating elements to be turned on.

[0057] If the toaster is in a "bread " mode, then heating elements on both internal plates are activated, so as to heat both sides of bread slices in the bread cage.

[0058] Once the food items have been toasted for a selected time, selected by use of the browning control, the meeting elements are turned off, and the bread cage is raised by the electric motor, so that the food pops up out of the top of the slot at the upper end of the heating chamber.

Cleaning the Heating Chamber -Cleaning Mode [0059] Referring to figure 14 herein, there is illustrated the heating chamber together with a cleaning tool, with the floor of the bread cage in a lowered position and the heating elements turned off. To clean inside of the heating chamber, there is provided a scraper/wand tool 1400, which can reach inside the heating chamber from the top of the heating chamber, and which can be moved up and down and across the inwardly facing surfaces of the internal heating plates 107, 108. To create access to the inside of the heating chamber, a user lifts out each of the first and second grids 118, 119 by grasping the projecting upper bar portionsl29, 130 of the respective grids, and sliding the grids upwardly and out of their slots or guides in their respective first and second frames.

[0060] The floor of the bed bread cage needs to be lowered to allow unobstructed access the cleaning inside the heating chamber. In the embodiment shown, the bread cage can be lowered by pressing a combination of the controls -112, 114 (the precise combination being programmable at manufacture) to activate a "cleaning function". The cleaning function means that the floor of the bread cage is lowered, without activating the electric heating elements.

[0061] With the floor of the bread cage lowered, and the grid sides of the bread cage removed, a user has good access for cleaning the inwardly surfaces of the first and second heating plates, using the cleaning tool provided. Since the frames 121, 122 of the bread cage each comprise a substantially rectangular hollow loop, frames do not interfere significantly with access to the surfaces of the class heating plates.

[0062] Additionally, any crumbs or debris which folds the floor of the heating chamber are collected in a crumb tray which extend substantially the full length and width of the heating chamber, underneath the heating chamber, and which can be slid out from the base portion 101 longitudinally, along a main length axis of the toaster.

Heating Gradient [0063] Referring to figure 15 herein, there is shown in view from one end, the pair of individual heating plates 107, 108, each having a corresponding respective thin film metal oxide semiconductor heating element 1500, 1501 coated onto one side. Figure 15 is not drawn to scale, in order to emphasise the changes in thickness of the metal oxide semiconductor film heating element, being relatively thicker at the lower regions of the heating plates compared to the upper regions.

[0064] If the heated plates were coated with a thin film heating element of uniform thickness, producing uniform energy density per unit area, and producing uniform heating across the plates, then because the plates are positioned either upright or vertically, and because heat rises, the top of the heating chamber would become hotter than the lower part of the heating chamber, leading to non -uniform browning of toast towards the top of the heating chamber.

[0065] To counteract this tendency, in the embodiment described herein each heating plate has a thin film heating element coating 1500, 1501 which is varied in thickness, being relatively thicker towards the lower regions 1502, 1503 of the plates, and relatively thicker towards the upper regions 1504, 1505 of the plates. Since the power output of the heating element depends upon its film thickness, the heating element towards the top of the plate, will have a lower per unit area power output than the heating element coating at the bottom of the plate.

[0066] In the embodiment shown, the thickness of the heating element is linearly tapered in thickness, with thickness increasing in a straight line from the bottom of the heated plate, towards the top of the heated plate, but in other embodiments, the thickness may be varied either in discrete steps of thickness, or in any other thickness profile which is capable of being economically manufactured, and which is designed to suit the individual heating chamber layout and dimensions. The design of the thickness profile of the heating element is such that the temperature on the sides of the bread or other item to be cooked is substantially uniform over the area of the bread sides, so that the food item cooks evenly.

[0067] Inner facing surfaces 1506, 1507 of the heating plates face inwardly towards the centre 1507 of the heating chamber. On the outer facing sides of the heating plates, there is deposited a thin film metal oxide semiconductor heating element, for example an antimony tin oxide (ATO) transparent heating element.

In the present embodiment, the film thickness of the metal oxide semiconductor layer is varied over the outer facing surface of the heating plate, so that the semiconductor film layer is thicker towards the bottom of the heating plate than at the top, in order to counteract the tendency of the top of the heating chamber to become hotter than the base of the heating chamber. Since the power density per unit area generated by the thin film metal oxide semiconductor layer is proportional to its thickness, a thicker layer generates relatively higher power densities than a thinner layer. Hence proportionally more energy per unit area is generated towards the lower parts of the heating plates, compared to the upper parts of the heating plates.

[0068] The precise thickness profile of the heating element layer is determined by the heat distribution profile within the heating chamber, the object being to achieve a substantially uniform temperature at all heights within the heating chamber, taking into account heat rises from the base of the heating chamber in heating up the upper part of the heating chamber. The exact thickness profile of the heating element is also dictated by the ease and cost of manufacture.

Contacts to the Thin Film Heating Element [0069] Referring to figures 16 to 18 herein, there is illustrated schematically an electrical contact mechanism for making contact with a thin film heating element deposited on a glass heating plate, as used in the present embodiment toaster.

[0070] Referring to figure 16 herein, each heating plate 107,108 is held securely along its base by a first mounting assembly 1601 which holds first ends of the heating plates, and a second mounting assembly 1602 which holds second ends of the heating plates, such that the plates are held in upright and parallel to each other in spaced apart relationship, such that the outer faces of the heating plates onto which are formed the thin film heating elements are on the outside of the heating chamber formed between the plates, and the inwardly facing surfaces 1507, 1508 of the respective heating plates present a flat glass surface forming 2 sides of the heating chamber.

[0071] The first and second mounting assemblies are substantially similar to each other. Taking the first mounting assembly 1601, this comprises a metal casting comprising a first upright channel or slot 1603, which is open at an upper end and closed off at a lower end for receiving a lower part of a first end of the first heating plate 107; a second upright channel or slot 1604 which is open atan upper end and closed off at a lower end, for receiving a lower pad of a first end of the second heating plate 108; and a rigid connecting member 1605 extending between the first and second channels/slots 1603, 1604.

[0072] Each channel/slot is formed having a hollow tubular casing or chamber 1606, within which an electrical contact is housed, along with a biasing means such as a spring which pushes the electrical contact against the heating plate located in the slot or channel. The lower end of the heating plate is held securely in the slot or channel, and the electrical contact has a degree of play or movement in a direction transverse to a main plane of the outer surface of the heating plate, so that the resilient biasing means pushes the electrical contact against an electrical conducting track 1607 formed on the outer surface of the heating plate.

[0073] Also within the upright slots or channels 1604, 1604 are provided electrically insulating inserts which securely hold lower parts of the first and second ends of the heating plates, whilst at the same time electrically insulating the heating plates from the surrounding mounting, except at the points where the electrical contacts connect with the conducting strips 1607, 1608 on the heating plates.

[0074] Referring to figure 17 herein, there is illustrated schematically in perspective view, the heating plates of figure 16, showing connection of the electrical contacts to electrical conducting strips 1607,1608 formed on the outer surfaces of the heating plates, absent of the mountings 1601, 1602.

[0075] The electrical contacts each comprise a substantially horizontally extending contact pin 1700 -1703 respectively. Each contact pin is held at one end of a compression spring, the other end of the compression spring being bonded to an upright contact plate 1704-1707 respectively. Each contact plate is bonded to an electrical wire, so as to deliver electrical power to the contact plates. The contact pins can move backwards and forwards along a main axial direction of the compression spring so as to urge the contact pin against the conductive tracks 1607, 1608 on the heating plates.

[0076] Each contact plate also has a screw 1708 -1709 which extends parallel to the contact pin and compression spring arrangement, and having its main length direction in a same direction as the contact pin. A distal end of each screw screws into the housing, securing the contact plate into the housing or chamber in which the compression spring and contact pin can slide so that the contact pin urges against an electrically conductive strip 1607, 1608 of the adjacent heating plate.

[0077] Referring to figure 18 herein, there is illustrated schematically the casing and movable contact pin arrangement in connection with an electrical conducting track of a heating plate. Also shown are portions of an electrically insulating material 1800 which line the channels all slots, to securely hold the lower ends of the heating plates lower portions of the heating plates at their ends.

[0078] In use, the casing is positioned adjacent to a heating plate 107, 108 such that the contact pin 1801 is urged against a thin film semiconductor coating 1607 on an outer side of the heating plate. The compression spring 1803 urges the contact pin to maintain physical contact with the outer surface of the thin film semiconductor heating element 1607 at all times, irrespective of any movement between the heating plate 107 and the casing. Preferably the contact pin is of copper or a similar material having good electrical conductivity.

[0079] The electrical contact pin and the compression are held within a tubular chamber which is closed off at a first end adjacent to one end of the compression spring, and open at a second end, such that the electrical contact at least partially protrudes from the second end and is movable backwards and forwards in a main axial direction of said chamber.

Claims

Claims 1. A toaster comprising: first and second upright heating plates; each said heating plate comprising a glass substrate; each said heating plate comprising a transparent thin film heating element; wherein said thin film heating element has film thickness which is relatively greater towards a lower region of said plate compared to a thickness of said heating element at an upper region of said plate.
2. The toaster as claimed in claim 1, wherein a film thickness of said heating element varies in a straight line linear manner between said lower region and said upper region.
3. The toaster as claimed in claim 1, wherein a film thickness of said heating element varies as a series of discrete steps of thickness between said lower region and said upper region.
4. The toaster as claimed in claim 1, wherein said heating element is applied as a continuous sheet across substantially a whole active heating area of said heating plate.
5. The toaster as claimed in any one of claims 1 to 4, wherein said toaster comprises a heating chamber formed between said first and second heating plates; and each said heating element is located on a side of said respective heating plate, which is facing a pair of the toaster as claimed in claim heating element is located on a side of said heating plate which is opposite to a side of said heating element which faces inwardly into said heating chamber.
6. A toaster comprising: a heating chamber for containing food items to be toasted; a food cage located in said toasting chamber for holding food items in said toasting chamber; said food cage comprising a base member capable of being raised or lowered; a drive motor and gearbox assembly for raising or lowering a said base member; and a connecting arm connecting an output shaft of said drive motor and gearbox assembly to said base member; wherein a first end of said connecting arm is connected to said drive motor, such that rotation of said drive motor causes a second end of said arm to raise or lower said base member; and wherein said first end of said connecting arm is connected to said drive motor at a position which is offset from a central plane bisecting said heating chamber.
7. The toaster as claimed in claim 6, wherein said motor and gearbox assembly comprises: an electric motor having a central rotational axis; and an output drive shaft, wherein a rotational axis of said output drive shaft is offset from said central rotational axis of said electric motor.
8. The toaster as claimed in claim 6, wherein said first end of said connecting arm is pivotally connected at a position which is eccentrically offset from a central drive rotational of said motor.
9. The toaster as claimed in any one of claims 6 to 8, wherein said base member is connected to a carriage; said carriage is movable up and down, so as to raise or lower said base member; said second end of said connecting arm locates with a corresponding slot or track of said carriage, and slides backwards and forwards along said slot or track as said connecting arm is raised or lowered, and as said carriage is raised or lowered.
10. The toaster as claimed in any one of claims 6 to 9, wherein, said connecting arm rotates in a first rotational direction, causing a second end of said connecting arm to slide between a first end of said slot/track of said carriage, and to a second end of said slot/track of said carriage, and to return to said first end of said slot/track of said carriage to raise said carriage from a fully lowered position to a fully raised position.
11. The toaster as claimed in any one of claims 6 to 10, wherein, said connecting arm rotates in a second rotational direction, causing a second end of said connecting arm to slide between a first end of said slot/track of said carriage, and to a second end of said slot/track of said carriage, and to return to said first end of said slot/track of said carriage to lower said carriage from a fully raised position, to a fully lowered position.
12. The toaster as claimed in any one of claims 6 to 11, wherein said second end of said connecting arm describes a semi -circular path when traversing between a fully raised position and a fully lowered position.
13. A toaster comprising: first and second heated plates, positioned opposite each other, and forming a chamber there between; each said heated plate comprising a transparent or translucent plate; each said heated plate having a transparent or translucent thin film heating element; an electrical power circuit for providing power to said thin film heating elements; a plurality of electrical contacts the connecting said electrical heating circuit to said thin film semiconductor heating elements; wherein at least one said electrical contact comprises a first electrically conducting part for touching against a part of a said thin film heating element, and thereby making electrical contact with said thin film heating element; and a resilient biasing means for urging said first electrically conducting part against said thin film heating element.
14. The toaster as claimed in claim 13, wherein said resilient biasing means comprises a compression spring.
15. The toaster as claimed in claim 13 or 14, wherein said resilient biasing means urges said electrical contact against a conducting track formed on said heated plate, in a direction transverse to a main plane of said heated plate.
16. The toaster as claimed in any one of claims 13 to 15, wherein said electrical contact and said compression are held within a housing having a tubular chamber, said tubular chamber being closed off a first end adjacent said compression spring, and open at a second end, such that said electrical contact protrudes at least partially from said second end and is movable backwards and forwards in a main axial direction of said chamber.
17. The toaster as claimed in claim 16, wherein said housing comprises part of a mounting block for mounting said first and second heating plates.
18. The toaster as claimed in claim 17, wherein said mounting block comprises first and second channels for holding respective lower portions of said first and second heating plates in spaced apart relationship to each other such that said first and second heating plates are held upright and parallel to each other forming a heating chamber there between.
19. The toaster as claimed in any one of claims 13 to 18, wherein said resilient biasing means comprises a compression spring; said electrical contact comprises a contact pin; said compression spring has a first end which is bonded to and in electrical contact with an electrical contact plate; said compression spring has a second end which is bonded to and in electrical contact with said contact pin; said electrical contact plate is bonded to an electrical conducting wire; and said electrical contact plate is mounted to a housing having a tubular chamber, such that said contact pin can move backwards and forwards along a main length axis of said tubular chamber, such that at least a portion of said electrical contact pin protrudes from an end of said housing sufficiently to be able to urge against a said transparent thin film heating element formed on a said heating plate.Amendment to the claims have been filed as follows Claims 1. A toaster comprising: first and second upright heating plates; each said heating plate comprising a glass substrate; each said heating plate comprising a transparent thin film heating element; wherein said thin film heating element has film thickness which is relatively greater towards a lower region of said plate compared to a thickness of said heating element at an upper region of said plate, and wherein a film thickness of said heating element varies in a straight line linear manner between said lower region and said upper region.2. A toaster comprising: first and second upright heating plates; each said heating plate comprising a glass substrate;II.....each said heating plate comprising a transparent thin film heating element; wherein said thin film heating element has film thickness which is relatively a. greater towards a lower region of said plate compared to a thickness of said heating element at an upper region of said plate, and wherein said heating element is applied as a continuous sheet across substantially a whole active heating area of said heating plate.3. The toaster as claimed in claim 1 or claim 2, wherein said toaster comprises a heating chamber formed between said first and second heating plates; and each said heating element is located on a side of said respective heating plate, said heating element is located on a side of said heating plate which is opposite to a side of said heating plate which faces inwardly into said heating chamber. * I. * * ***S * S I. * * * * * ., * * * * S S * S. *0S