The invention relates to toasters that have automatic lifting and lowering mechanisms for the bread.
While toasters are sometimes used to toast pastries, muffins and other foods they predominately toast slices of bread and the invention will be described with reference to this primary use. However, terms such as “bread carriage” are not to be construed as restricting the toaster to use with bread as toasters are equally suitable for a range of other food products.
The majority of modern toasters have two or more upwardly facing slots for receiving slices of bread. These slots lead to respective bread carriages within the body of the toaster. The bread carriages are in an elevated position when the slice is placed through the slot so that a significant portion of the bread is left protruding from the toaster body. To toast the bread, the carriage is moved from the elevated position to a lowered position for simultaneously toasting both sides of the slice.
Traditionally the carriage is moved manually by the user to the lowered position. More sophisticated toasters have a mechanism to actively move the carriage between the elevated position and the lowered position and vice versa (see, for example U.S. Pat. No. 8,336,449 B2). This mechanism may use a motor to elevate and lower the carriage, but the addition of these components requires careful consideration to shield them from the heaters during the toasting operation. Other toasters have used horizontal expansion and contraction of the heating elements to assist the movement of the bread carriage (see, for example U.S. Pat. No. 2,590,334 and AU 4170878). Converting the horizontal expansion of heater elements to a vertical movement requires a complex mechanism. The complexity of the mechanism inherently increases the mechanical losses and the efficiencies in converting horizontal expansion to vertical lifting forces acting on the bread carriage. Furthermore, the horizontal heating wires for toasting the bread need flexible tensioning mechanisms to keep them flat against a supporting panel of thermally insulating heat shields (typically made of mica). Without tensioning the heating wires, they can bow outwards as they thermally expand which can lead to contact between adjacent wires resulting in a short circuit.
With the above issues in mind, one aspect of the present invention provides a toaster for toasting bread or other food, the toaster comprising:
Preferably, the heating panel has an electrical conductor defining a series of generally vertical conductive paths spaced across the heating panel such that resistive heating of the electrical conductor causes thermal expansion to move the heating panel to the expanded form.
Preferably, the heating panel has a thermal insulation card and the electrical conductor is a heating wire supported on the card in a serpentine configuration such that the generally vertical conductive paths are spaced across one side of the card facing the carriage.
Preferably, the heating panel has a bottom bracket connected to the linkage assembly, and the heating panel is mounted within the body such that the bottom bracket moves downward in response to the thermal extension to the expanded form.
Preferably, the thermal insulation card has an upper portion and a lower portion, the lower portion being configured to move downward relative to the upper portion in response to the thermal expansion.
Preferably, the thermal insulation card is formed from mica and the heating wire is a nichrome alloy.
Preferably, the linkage assembly has a plurality of levers connected in series such that downward movement of the bottom bracket is amplified to greater downward movement of the bread carriage.
Preferably, the downward movement of the bottom bracket is controllable by varying electrical power supplied to the heating panel.
Preferably, the linkage assembly has a first fulcrum fixed to the body and a first lever with a first lever input arm pivotally connected to the bottom bracket and the first fulcrum, and an output lever arm fixed to the first input lever arm, the first input lever arm being shorter than the first output lever arm, and,
The linkage assembly may alternatively comprise two linkage sub-assemblies.
The two linkage sub-assemblies are preferably mirrored. The two linkage sub-assemblies are also preferably disposed at opposing ends of the bread carriage.
Each linkage sub-assembly may include:
Another aspect of the invention provides a method of operating a toaster with a body and a carriage movable between an elevated position and a lowered position within the body, and a heating panel for toasting a slice of bread on the carriage, the method comprising:
after a pre-set time period, determining whether the carriage is at the lowered position;
Preferably, the pre-set time period is between 1 second and 4 seconds.
Preferably, the carriage moves from the lowered position during the predetermined toasting cycle.
Preferably, the toaster further comprises bread guards as a barrier between the bread and the heating panel, and the moves from the lowered position during the predetermined toasting cycle to reduce visible grill marks on the slice caused by the bread guards.
Preferably, the heating panel thermally expands when activated and this expansion moves the carriage such that the carriage is moved from the lowered position during the predetermined toasting cycle by varying power to the heating panel.
Preferably, the toaster generates an alert in response to a determination that the carriage is not at the lowered position after the pre-set time period elapses from the activation of the heating panel.
In a third aspect, the invention provides a toaster for toasting bread or other food, the toaster comprising:
Preferably, the lift mechanism is provided by the heating panel and a linkage assembly, the linkage assembly connecting the heating panel to the carriage, and the heating panel has a contracted form when not toasting bread, and an expanded form when toasting bread, the heating panel having a vertical dimension in the contracted form that is less than the vertical dimension in the expanded form, and the linkage assembly is configured to move the carriage from the elevated position to the lowered position when the heating panel moves from the contracted form to the expanded form.
Preferably, the heating panel has an electrical conductor defining a series of generally vertical conductive paths spaced across the heating panel such that resistive heating of the electrical conductor causes thermal expansion to move the heating panel to the expanded form.
Preferably, the processor is configured to move the carriage during the toasting cycle by varying electrical power to the heating panel.
Preferably, the heating panel has a thermal insulation card and the electrical conductor is a heating wire supported on the card in a serpentine configuration such that the generally vertical conductive paths are spaced across one side of the card facing the carriage.
Preferably, the heating panel has a bottom bracket connected to the linkage assembly, and the heating panel is mounted within the body such that the bottom bracket moves downward in response to the thermal extension to the expanded form.
Preferably, the thermal insulation card has an upper portion and a lower portion, the lower portion being configured to move downward relative to the upper portion in response to the thermal expansion.
Preferably, the thermal insulation card is formed from mica and the heating wire is a nichrome alloy.
Preferred embodiments of the present invention will now be described by way of example only with reference to the accompany drawings in which:
Referring to the Figures, a toaster 2 for toasting slices of bread 8 is depicted and described in detail. However, it will be appreciated the toaster may toast or heat other food products such as pastry, muffins, crumpets and so on. As shown in
The first and second guide rails 12 and 14 may be fixed to a supporting base 20 provided by the body 4 of the toaster 2. The heater panel 10 may also be fixed to the body 4 such that the first and second side edge channels 22 and 24 are fixedly secured relative to the base 20 and the body 4. The edge channels 22 and 24 hold the side edges of a thermally insulating card 18 which is typically formed from mica which contains aluminosilicate minerals to resist high temperatures and provides a good insulator. This may at least protect the components outside the toasting cavity from excessive temperatures that may cause damage or risk burning the user.
The mica card 18 may be provided in two portions with an upper portion 32 abutting the lower portion 34 along a split line 30 when the bread carriage 16 is in the elevated position. While the upper portion 32 of the mica card 18 is fixed in the side edge channels 22 and 24, the lower portion 34 is free to slide within the side edge channels 22 and 24. A bottom bracket 36 extending along the lower edge of the mica card 18 also moves together with the lower portion 34 relative to the upper portion 32.
The top and bottom edges of the mica card 18 may have a series of spaced edge grooves 28. An electrically conductive heater in the form of resistive heating wire 26 is wound onto the mica card 18 in a serpentine configuration to provide a series of generally vertical conductive paths 27. Activating the heater panel 10 provides current to the heater wire 26 to generate resistive heating. As the heater wire 26 increases in temperature, it expands in accordance with its coefficient of thermal expansion. One example of heater wire with suitable resistive properties as well as sufficient coefficient of thermal expansion, is nichrome metal alloy wire.
With the heater wire 26 configured such that it predominantly extends in a vertical direction, the thermal expansion of the heater wire 26 is likewise in the vertical direction. As shown in
In the first embodiment of the linkage assembly 53 having two interconnected levers (as best shown in
The linkage arm 46 connects the first lever to the second lever. Specifically, the linkage arm 46 connects the first output arm 42 to the second input arm 54 of the second lever which pivots about a second fulcrum 55. The second input arm 54 extends from a pivot connection to the linkage arm 46 to the second fulcrum 55 while the second output arm 52 extends from the second input arm 54 to the carriage lifter 48 attached to the bread carriage 16. As the distal end of the second output arm 52 moves in an arc, an elongate slot 50 is provided to slidably retain the end of the bread carriage lifter 48.
To facilitate or amplify the vertical movement of the heater panel 10 between its retracted form and expanded form, the linkage assembly 53 is configured such that the first input arm 44 is shorter than the first output arm 42, and the second input arm 54 is shorter than the second output arm 52. As shown in
It will be appreciated that the second embodiment of the linkage assembly 53 having the pair of linkage sub-assemblies 53a and 53b with each sub-assembly 53a, 53b having two interconnected levers (as best shown in
As shown in
Similar to the first embodiment of the linkage assembly 53 described above, the second embodiment of the linkage assembly 53 having the pair of linkage sub-assemblies 53a and 53b may be duplicated such that a mirrored linkage assembly “set” may be provided for each of the opposing heater panels 60, 70. Accordingly, in this arrangement, both sets of mirrored linkage assemblies 53 may operate in parallel/tandem to further facilitate or amplify the movement of the bread carriage 16. It will also be appreciated that the provision of the dual linkage sub-assemblies 53a and 53b may at least increase the lifting power of the linkage assembly for moving the bread carriage 16, such that heavier loads (e.g. heavier breads) may be lifted, and also lowered.
As best shown in
Detection of bread on the carriage 16 by the sensor 58 activates the heating panels 60) and 70 (step 100). As the heating wire 26 rapidly heats and expands, the sensor 58 is configured to wait a pre-set time, for example between 1 second and 4 seconds, and preferably approximately two seconds, before checking whether the carriage 16 has lowered (step 102). If the controller 62 determines the bread carriage has lowered (determination 104), the toaster 2 will continue toasting both sides of the bread slice simultaneously until completion of the toasting cycle (step 106). If the processor 62 determines that the bread carriage 16 has not lowered from the sensor 58 feedback, power to the heating panels 60 and 70 associated with the slot 6 is discontinued until the next toasting cycle (step 108) to avoid wasting power. The controller 62 may also provide an alert as a warning or to remind the user that the bread is not within the slot or the bread is not correctly positioned within the slot. This alert may be communicated to the user via a user interface. The user may be able to customise the sensor sensitivity based on a particular type of bread they prefer. For example, bread with a light weight may cause small movement of the bread carriage, which requires high sensor sensitivity.
14A and 14B show the lift mechanism (provided by the heating panel 10 and the linkage assembly 53) being used to reduce or avoid the appearance of grill marks 68 on a slice of toast 8. Grill marks 68 on the toast result from guard elements 66 in the bread guard 68 masking or ‘shading’ the bread surface from radiant heat from the heater panel 10. During the toasting cycle, the vertical position of the bread slice 8 within the toaster can be varied by adjusting power to the heater panel 10.
Varying the position of the slice 8 during may be achieved by adjusting the power to the heater wire 26, thereby increasing or decreasing the thermal expansion of the wire and hence the bread carriage 16 position. The amount of variation of power to the heaters may depend on the type of the bread and/or the user-selected toasting shade. Optionally, the user may manually input the variation of the position of the slice 8, and the timing of any variations, via the user interface (not shown).
The present invention has been described herein by way of example only. Skilled workers in this field will readily recognise many variations and modifications which do not depart from the spirit and scope of the broad inventive concept.
Number | Date | Country | Kind |
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2021902985 | Sep 2021 | AU | national |
Filing Document | Filing Date | Country | Kind |
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PCT/AU2022/051118 | 9/16/2022 | WO |