The present invention relates generally to toasters, and more particularly to toasters including one or more thin-film heating elements.
A toaster typically includes a housing that has at least one slot configured to receive a slice of bread or other food product to be toasted. A basket is disposed underneath each slot to retain the food product. When the toaster is activated, typically by depressing a vertical slider button, the food product is lowered within the basket into a heating box. In at least some known toasters, the heating box is located within about 6.35 mm (0.25 in.) of a base of the toaster to minimize a vertical profile of the toaster.
Within the heating box, heating units disposed on each side of the basket apply heat to the respective sides of the food product. At least some known toaster heating units utilize a filament wrapped around a heat-resistant board, wherein the filament radiates heat at infrared wavelengths when a current is applied to it. Typically, a control circuit determines the length of the heating operation based on a user control setting.
Satisfactory toasting of bread and other food products involves removing moisture from the food product. Because fresh bread and other fresh food products often contain a significant amount of moisture, satisfactory toasting traditionally has required several minutes of heating. Efforts to decrease the required heating time have been limited by several factors. For example, at least some known toaster heater units use iron-chromium filaments. However, iron-chromium tends to radiate in a portion of the infrared spectrum that is relatively inefficient at transferring energy to the food product.
Another factor is that in at least some known toasters, heat dissipates from the outside edges of the heating box more quickly than from the center. Thus, with regard to baskets adjacent to the outer wall of the toaster, the side of the food product facing the outer wall tends to brown more slowly than the side of the food product facing the interior of the toaster. This problem is exacerbated when the radiated power is increased in an attempt to speed the toasting process.
In addition, known attempts to decrease the time needed for satisfactory toasting have been limited by the fact that moisture released from the food product, in the form of water vapor (i.e. steam), absorbs a portion of the infrared radiation emanating from the heating unit throughout the toasting process. If more power is applied to the heating unit in an attempt to speed up the toasting process, correspondingly more steam is generated early in the process, thus absorbing more of the infrared radiation output from the heating unit and extending the process again.
There is a need, therefore, for an improved toaster with heating elements that are able to heat up and toast food products more quickly.
In one embodiment, a toaster generally comprises at least one thin-film heating element, the thin-film heating element including a resistive film coupled to a substrate and extending between a pair of electrical conductors.
In another embodiment, a method of toasting a food product generally comprises placing the food product in a toaster including at least one thin-film heating element, the thin-film heating element including a resistive film coupled to a substrate and extending between a pair of electrical conductors, and toasting the food product using the toaster.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
The systems and methods described herein employ a thin-film heating element as part of a toaster, such as a vertically-oriented bread toaster with the bread exiting from either the top or bottom of the toaster, a horizontally oriented toaster, and a single or multi-slice bread toaster (collected identified as a “toaster” herein). Integrating the thin-film heating element into the toaster creates unique aesthetic and functional design aspects.
The embodiments described herein include toasters including one or more thin-film heating elements. As used herein, a thin-film heating element refers to an electrically conductive material (e.g., a conductive film) deposited on a substrate (e.g., a ceramic glass substrate) for heating the substrate. The heating element is said to be a “thin-film” heating element in the sense that the substrate and the electrically conductive material have a collective thickness that is only marginally greater than the substrate itself (i.e., the material forms a thin film on the substrate).
The thin-film heating element may include, for example, a metal oxide (e.g., tin oxide) resistive film bounded on opposing edges by electrical conductors, such as electrical bus bars or wires. The bus bars or wires may connect to a controller and power source to run current through the resistive film to generate heat. Specifically, by applying a voltage between the bus bars or wires, current flows through the resistive film, heating the resistive film and the substrate on which the resistive film is deposited. Using a thin-film heating element improves power efficiency, heating uniformity, and speed of heating. Further, the thinness and conductive heat directionality of a thin-film heating element also permit a cooking appliance, such as a toaster, to have a thinner profile.
As described herein, in at least some embodiments, a toaster includes transparent windows (e.g., made of ceramic glass). The thin-film heating element may be combined with the transparent windows or on a separate substrate. In either case, the windows provide visual inspection of the toast being heated within the toaster.
With reference now to the drawings and in particular to
As shown in
Referring back to
In this embodiment, the base 114 includes a tool slot 120 configured to store a toast removal tool 122 therein. Once bread is toasted in the toaster 100, a user can use the toast removal tool 122 to push toast out of the toaster 100. The toast removal tool 122 includes a pointed end 124 for contacting the toast and a handle end 126 sized to rest in the tool slot 120.
As shown in
Each thin-film heating element 302 includes a resistive film 308 and bus bars or wires (neither shown) electrically coupled to the resistive film 308. Using the bus bars or wires, a current is run through the resistive film 308 to heat the resistive film 308 and consequently, the inner panel 306. Upper and lower support bars 310 and 312 extend between the outer panels 304. The transparency of the thin-film heating elements 302, the outer panels 304, and the inner panels 306 allow a user to see through the toaster 300, and allow the user to observe a food product during toasting.
Referring back to
In this embodiment, the toaster 300 also includes a control panel 330 including one or more input interfaces 332 (e.g., buttons) that enable a user to control operation of the toaster. For example, the user may be able to specify a toasting time, a shade level, or other parameters. When the user sets a toasting time, once that toasting time is reached, the support tray 322 moves from the lowered position to the raised position, ejecting the food product from between the inner panels 306. In some embodiments, the control panel 330 includes an eject button that allows a user to eject the food product once the eject button is pressed, regardless of whether a previously set toasting time has been reached.
The toaster 500 includes a substantially transparent outer casing 504 and a pair of substantially transparent panels 506. In this embodiment, as shown best in
Each thin-film heating element 502 includes a resistive film 510 and bus bars or wires (neither shown) electrically coupled to the resistive film 510. Using the bus bars or wires, a current is run through the resistive film 308 to heat the resistive film 510 and consequently, the panel 506 that the resistive film 510 is coupled to. The transparency of the thin-film heating elements 502, the casing 504, and the panels 506 allow a user to see through the toaster 500, and allow the user to observe a food product during toasting.
As shown in
The toaster 500 includes an opening 520 at the top of the toaster 500 where the toast is inserted. A lever 522 allows a user to lower the toast into the toaster 500, similar to a conventional toaster. Once the toast is sufficiently heated within the toaster 500, the toast is released from the toaster 500 and slides out a chute 524 at the bottom of the toaster 500. Accordingly, if the user positions a plate in front of the chute 524, the dispensed toast will slide out of the chute 524 onto the plate. A pair of legs 523 extend downward from a base 525 of the toaster 500 to provide space for the chute 524.
Specifically, as shown in
In this embodiment, the toaster 500 also includes a control panel 530 (e.g., on the base 525) including one or more input interfaces 532 (e.g., buttons) that enable a user to control operation of the toaster. For example, the user may be able to specify a toasting time, a shade level, or other parameters. When the user sets a toasting time, once that toasting time is reached, the trap doors 526 open, dispensing the toast from the toaster 500. In some embodiments, the control panel 530 includes an eject button that allows a user to eject the toast once the eject button is pressed, regardless of whether a previously set toasting time has been reached.
In this embodiment, the toaster 500 includes a temperature control system. Notably, it has been experimentally verified that there is a substantially linear relationship between a current conducted through a thin-film heating element 502 and a temperature of the thin-film heating element 502.
Accordingly, by measuring the current conducted through the thin-film heating element 502, the approximate temperature of the thin-film heating element 502 can be calculated using the linear fit 1002 and the measured current. In this embodiment, a resistor is electrically coupled in series with each thin-film heating element 502. By dividing a voltage across the resistor by a resistance value of the resistor, the current through the associated thin-film heating element 502 can be measured.
In this embodiment, the temperature control system can be implemented using a microcontroller (not shown) included within the toaster 500. Specifically, for each thin-film heating element 502, the microcontroller divides the voltage across the resistor by the resistance value of the resistor to calculate the measured current, and calculates the approximate temperature based on the linear relationship and the measured current.
The microcontroller may, for example, control the current through each thin-film heating element 502 to control the temperature of the thin-film heating element 502. In one example, the microcontroller ensures that a temperature of each thin-film heating element 502 does not exceed a predetermined maximum temperature (e.g., 400° Celsius). Specifically, when the approximate temperature calculated by the microcontroller reaches or approaches the predetermined maximum temperature, the microcontroller decreases the current through the thin-film heating element 502 (e.g., by decreasing the applied voltage) such that the approximate temperature is reduced. In this embodiment, the average voltage is decreased. Specifically, a peak voltage level remains the same, but the number of cycles during which the peak voltage level is applied is reduced. Accordingly, over a period of time, the average voltage (and accordingly, the average current) is reduced.
A basket 1115 is disposed generally underneath each slot 1113 within housing 1103. Each basket 1115 is configured to receive the food product through the corresponding slot 1113 and retain the received food product in position during the toasting process. In addition, a vertical slider button 1117 is disposed on a front surface 1119 of the housing 1103. The button 1117 is operably coupled to each basket 1115 in conventional fashion. More specifically, when the button 1117 is depressed, the received food product (not shown) is lowered within each basket 1115 such that substantially all of the received food product is disposed within the housing 1103. The button 1117 may be coupled to the baskets 1115 in any suitable fashion. In alternative embodiments, any suitable control may be used to lower the received food product within each basket 1115.
In the illustrated embodiment, a browning control selector 1121 and a plurality of user buttons 1123 also are disposed on front surface 1119. The browning control selector 1121 is configured in conventional fashion to enable a user to select a desired degree of toasting (i.e., corresponding to a desired shading) to be performed. The user buttons 1123 are configured in conventional fashion to allow the user to control other toaster functions, for example, identifying a type of food product (e.g. bread, bagel, etc.) to enable optimization of the toasting process, popping the food product within each basket 1115 up through the corresponding slot 1113 and manually ending the toasting process, etc. In alternative embodiments, the toaster 1101 may have a plurality of vertical slider buttons 1117, browning control selectors 1121, and sets of user buttons 1123 each associated with a subset of the slots 1113.
At least one vent 1161 is disposed on the upper housing portion 1105 of the toaster 1101. In the illustrated embodiment, a vent 1161 is disposed near each respective opposite end of the top surface 1111 of the housing 1103. Each vent 1161 includes a plurality of elongated openings 1163 extending through the housing 1103. The vents 1161 facilitate air circulation through the interior of the housing 1103.
Referring now in particular to
In this embodiment, the two outer heating units 1131, the bottom plate 1135, the front plate 1137, and the back plate 1139 are configured such that the side surfaces of the heating box 1129 are not sealed. More specifically, apertures 1141 are present between each outer heating unit 1131 and the front plate 1137, and between each outer heating unit 1131 and the back plate 1139.
Additionally or alternatively, apertures 1143 are defined in the front plate 1137 and the back plate 1139.
In this embodiment, the heating box 1129 is coupled to the base 1109 of the toaster 1101. More specifically, a plurality of posts 1151 extend upward from the base 1109 and couple to the bottom plate 1135 of the heating box 1129. Each post 1151 is coupled to the base 1109 and to the bottom plate 1135 using a suitable fastening structure. A washer 1153 formed from a suitable insulating material, such as, but not limited to, mica, is disposed between each post 1151 and the bottom plate 1135 to facilitate insulating the heating box 1129 from the base 1109.
In the illustrated embodiment, a length 1155 of the posts 1151 is extended beyond a minimum length required for insulation purposes. Due to the extended length 1155, a cavity 1157 is defined between the bottom plate 1135 and the base 1109. The cavity 1157 facilitates airflow through the interior of the housing 1103. In another embodiment, the length 1155 is in a range of about 12.7 mm (0.5 in.) to about 15.875 mm (0.625 in.). In another embodiment, the length 1155 is about 12.7 mm (0.5 in.).
An inner heating unit 1133 is disposed within heating box 1129 between the adjacent pair of baskets 1115. The inner heating unit 1133 is coupled to at least one of the bottom plate 1135, the front plate 1137, and the back plate 1139. In this embodiment, the inner heating unit 1133 does not include a thin-film heating element. Instead, the inner heating unit 1133 includes a board formed from a suitably heat-resistant material, such as mica, with a pattern of wire filament disposed on both sides of the board. In
With reference to
In some embodiments, a user may control toasters 100, 300, 500, and 1100 using a computing device (e.g., a tablet, a desktop computer, a laptop computer, a mobile phone, etc.), where the computing device communicates remotely with the toaster over a wired and/or wireless network, such as the Internet, or any other communications medium (e.g., Bluetooth®). For example, the user may use a software application on a computing device that enables the user to set a toasting time, where the input is communicated from the computing device to the toaster. Further, the toaster may communicate information to the computing device (e.g., remaining toasting time) to notify the user.
When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
This application claims the benefit of U.S. Provisional Application No. 61/980,468 filed Apr. 16, 2014, and U.S. Provisional Application No. 62/040,213 filed Jul. 10, 2014, both of which are incorporated herein in their entirety.
Number | Date | Country | |
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61980468 | Apr 2014 | US | |
62040213 | Aug 2014 | US |