Abstract:
The invention relates to a toaster. The toaster comprises a thermally insulating box, a mobile housing to receive a slice or piece of bread, and at least one heat element. Each one of the side walls of the thermally insulating box comprises two transparent plates and a space being provided between the two plates to form a wall. The heating element utilizes infrared radiation and is equipped with at least one means for preventing a portion of the radiation from diffusing towards the bread.

Description:
TECHNICAL FIELD OF INVENTION 
       [0001]    The present invention refers to a household device such as a toaster. 
       BACKGROUND OF THE INVENTION 
       [0002]    This wide-spread kind of device generally comprises a thermally insulating box forming the body of the device. This box contains at least one heating element, for example one or more resistors connected to a source of electric voltage. The box also contains a mobile housing in which a piece of bread to be toasted is placed, said housing being located near the resistors. The resistors are heated during a given time, after which the piece of toast is ejected from the device. 
         [0003]    It is in particular known to include the resistors in tubes of quartz, in order to prevent the user from coming into contact with a naked conductor. 
         [0004]    A toasting level of the bread is chosen by the user, classically by means of a cursor or of a serrated roller, before introducing the bread into the device. However, said cursor or said serrated roller is generally connected to means for determining the toasting duration. This duration, often approximate, does not correspond to a precise toasting quality for the bread. Indeed, for the same toasting duration, the result obtained in terms of visual aspect and taste varies according to the nature of the bread introduced. Variation factors are in particular the thickness of the bread slice and its percentage of moisture. 
         [0005]    It is thus useful to be able to control visually the toasting progression for the bread, in order to stop it when it reaches the level desired by the user. A solution to this problem is provided by the invention described in the patent FR 2 799 632, in the name of the Applicant. This invention relates to a toaster whose side walls of the box are transparent. Thus, the bread slices introduced into the device can be seen during their toasting which can thus be stopped at the desired time. 
         [0006]    According to a variant of the invention described in the patent FR 2 799 632, the heating elements are arranged in the upper and lower parts of the box, in order to clear the median part of said box. In this manner, the heating elements are not very visible by the user. He can thus control the toasting level for a piece of bread without its field of vision being obstructed by the presence of a heating element. 
         [0007]    A disadvantage of positioning the heating elements outside the median part of the box is related to the toasting quality for the bread. Indeed, a bread slice introduced into such a device is more toasted near the heating elements, that is to say at the top and at the bottom, than in its median part. One thus obtains a not very homogeneous toasting, which is unsatisfactory for the consumer. 
         [0008]    A known solution, described in the patent FR 2 799 632 consists in including the heating elements into reflector housings. These reflector housings have a generally bent shape, able to reflect a part of the infrared radiation of the resistors towards the bread slices, in particular towards their median part. These reflectors thus enable to homogenize the toasting of the bread if the heating elements are placed at the top and at the bottom of the box. 
         [0009]    However, it happens that the result obtained is not sufficiently homogeneous for the taste of the consumer. There is thus a need to control the toasting level according to the zone of the bread slice. 
         [0010]    Another disadvantage related to the position of the heating elements relates to the bread crumbs falling to the bottom of the device. Indeed, when introducing or ejecting the bread, crumbs can fall onto the heating elements and, if necessary, onto the reflectors. The heating elements concerned are mainly those being in a lower part of the box. 
         [0011]    Because of their shape, in particular curved, the reflectors which receive bread crumbs keep these crumbs in the vicinity of, even in contact with, the heating elements. During toasting, these crumbs are brought up to a very high temperature. They calcine and give off smoke, which causes an embarrassment for the consumer and a risk of starting a fire. 
         [0012]    Moreover, this calcination leaves unaesthetic traces on the heating elements and the reflectors. If the box is transparent, the interior of the device can be seen by the user. It is thus preferable to avoid the appearance of such traces of calcinations on the reflectors. 
       OBJECT AND SUMMARY OF THE INVENTION 
       [0013]    The present invention enables to solve these various problems. The invention refers to a toaster comprising a thermally insulating box, a mobile housing intended to receive a piece of bread, at least one infrared radiation heating element; said toaster being characterized in that at least one heating element is equipped with at least one means for preventing a part of the radiation from diffusing towards the bread. 
         [0014]    According to an embodiment of the invention, at least one radiation heating element comprises a reflector housing, said reflector housing enabling to reflect a part of the radiation towards the bread to be toasted, and a part of a surface of said reflectors is equipped with means for preventing the radiation from being reflected towards the bread. According to this embodiment of the invention, the radiation is partially prevented from diffusing by reflection towards the bread. 
         [0015]    The means for preventing the radiation from being reflected can consist of a non-reflective material, applied to a part of the surface of the reflector. This material can in particular be a varnish or paint. These means can also consist of another treatment of the surface of the reflector, such as a grinding or a local deformation. 
         [0016]    According to a preferential embodiment of the invention, the means for preventing the radiation from being reflected are through holes, provided in the surface of the reflectors. 
         [0017]    According to another embodiment of the invention, at least one radiation heating element comprises a wall arranged between the heating element and the mobile housing. Said wall absorbs a part of the radiation diffused towards the bread. Thus, the direct radiation is partially prevented from diffusing towards the bread. 
         [0018]    According to a preferential embodiment of the invention, the wall comprises a surface having at least one absorbance gradient for the infrared radiation. Thus, according to the zone of the wall considered, the absorbance is different. The intensity of the infrared radiation diffused towards the bread is thus modulated according to the zone of the piece to be toasted. 
         [0019]    Such an absorbance gradient can be obtained by a variable thickness of the wall. The wall can also be made of several materials having different absorbances. 
         [0020]    According to a preferential embodiment of the invention, the wall is made of a material which is transparent or translucent for the visible light. In particular a wall made of mica can be used. According to another embodiment, the wall is made of a material which is opaque for the visible light, such as for example PTFE (polytetrafluoroethylene). 
         [0021]    According to an embodiment of the invention, the wall has one or more continuous surfaces. In order not to lengthen in a too important way the durations necessary to toast the bread, it is preferable to use a wall made of a material enable the passage of a sufficient part of the infrared radiation. 
         [0022]    According to another embodiment of the invention, said wall comprises one or more perforations, in order to modulate the intensity of the infrared radiation received by one part of the piece of bread to be toasted or other. 
         [0023]    According to a preferential embodiment of the invention, said wall is a grid. Such a grid is formed for example of metal wires. The provision of said wires enables to modulate the intensity of the infrared radiation received by one part of the piece of bread to be toasted or other. 
         [0024]    In addition to its function of regulation of the infrared radiation diffused towards the bread, such a wall enables to prevent bread crumbs from being in contact with the heating element. If the heating element is equipped with a reflector, this wall can also prevent bread crumbs from accumulating onto the reflectors, in the vicinity of, or in contact with, the heating element. This function of protection against crumbs particularly relates to the heating elements which are in a lower part of the toaster. 
         [0025]    It is known to equip the heating elements of grill ovens with such walls. However, these walls then have a function of mechanical protection against shocks, during the introduction of hard objects, such as dishes, inside the oven. These walls also have a function of protecting the user against a possible electrical contact in the event of a rupture of the heating element. 
         [0026]    This function is useless in a toaster. Indeed, it is not intended for the introduction of hard objects or of the hand of a user. 
         [0027]    The invention is of particular interest for toasters whose heating elements are positioned at the top and at the bottom of the device, in particular when the walls of said toaster are transparent. 
         [0028]    However, the invention can be applied to any type of toaster, whatever the position of the heating elements. Generally, the invention enables to control the radiation of the heating elements towards a certain part of the bread to be toasted. Such an invention in particular enables to adopt an asymmetrical arrangement of the heating elements, for example by gathering them in an upper part of the device, while ensuring a homogeneous toasting of a bread slice. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The invention will be better understood from the reading of the following description and the examination of the annexed figures. Those are given as an indication and by no means a limitation of the invention. 
           [0030]      FIG. 1 : a sectional view of a toaster according to an embodiment of the invention; 
           [0031]      FIG. 2 : a cavalier projection of a heating element and a reflector according to an embodiment of the invention; 
           [0032]      FIG. 3 : a cavalier projection of a heating element and a reflector according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0033]      FIG. 1  represents a sectional view of a toaster according to an embodiment of the invention. 
         [0034]    The toaster  1  comprises a box  2 , having a substantially parallelepipedic shape. Said box is provided, in its upper part, with a slit  3  through which one or more slices of bread  4  can be introduced. A slice of bread  4  introduced into the toaster  1  is supported by a mobile housing  5 , which can be translated vertically. Such a mobile housing  5  is used in a traditional way in the majority of the known toasters. In  FIG. 1 , the housing  5  is represented in a low position. The housing  5  is in particular in this low position during the operation of the heating elements ( 9 ,  10 ) of the toaster  1 . When ejecting the bread, the housing  5  moves to a higher position. 
         [0035]    The mobile housing  5  consists for example of metal wires spaced from each other, in order not to make obstacle with the bread toasting. In a preferential way, the mobile housing  5  comprises vertical wires arranged side by side. In a more preferential way, two adjacent wires are spaced with a maximal distance of 19 mm. 
         [0036]    The housing  5  is in a median position in the box, relative to the side walls ( 6 ,  7 ). In the example in  FIG. 1 , the walls ( 6 ,  7 ) are transparent. More precisely, the walls ( 6 ,  7 ) are transparent for the visible light. Each one of these walls are composed of two transparent plates ( 61 ,  62 ;  71 ,  72 ), for example glass plates. A space  8 , provided between both plates forming a wall, forms heat insulation between the inside and the outside of the box  2 . In a preferential way, two transparent plates ( 61 ,  62 ) forming a wall are spaced with a distance of at least 2 mm. 
         [0037]    According to the embodiment represented in  FIG. 1 , the walls ( 6 ,  7 ) are fixedly assembled on the box  2 . According to another embodiment of the invention, at least one wall  6  or  7  is mobile in rotation relative to the box  2 , for example relative to an axis perpendicular to the sectional plane in  FIG. 1 . Said mobile wall then forms a gate which enables to easily reach the inside of the box, for example for cleaning operations. 
         [0038]    According to another embodiment of the invention, at least one wall  6  or  7  is assembled in a removable way relative to the box  2 . More particularly, at least one wall  6  or  7  is fixed to the box  2  by means of a reversible assembly, for example clips. 
         [0039]    Preferentially, if a wall ( 6 ,  7 ) is mobile in rotation or removable relative to the box  2 , the toaster  1  is equipped with a safety system. This system switches off the power supply of the toaster when at least one of the walls ( 6 ,  7 ) is not in a closed position. 
         [0040]    On each side of the mobile housing  5  are arranged heating elements  20 , comprising for example heating resistors ( 9 ,  10 ). More precisely, each side of the mobile housing  5  comprises two heating resistors ( 9 ,  10 ). Advantageously, the resistors ( 9 ,  10 ) are included in tubes  11  of quartz, which improves the infrared radiation. 
         [0041]    In order not to enter the field of vision of a user, the resistors  9  are located in the upper part of the box  2 , while the resistors  10  are located in the lower part of the box  2 . Thus, an observer located at the height of the transparent walls ( 6 ,  7 ) can clearly see the bread slices  4 . He can thus evaluate in an optimal way the toasting level of said slices  4 . 
         [0042]    The positioning of the resistors ( 9 ,  10 ) at the top and at the bottom of the box tends to generate a greater toasting level in the upper and lower parts of the bread slice  4  than in the median part of said slice. In order to standardize the quantity of infrared radiations received by all the surface of the bread, it is provided around each tube  11  of quartz a reflector  13 , which directs the infrared radiation  50  towards the bread, in particular the median part  12  of the slice  4 . 
         [0043]    However, a part of the reflector  13 , in particular near the nearest edge  14  from the mobile housing  5 , also reflects the infrared radiation toward the upper or lower part of the slice  4 . 
         [0044]    In order to standardize the quantity of infrared radiation received on all the surface of the slice  4 , it is thus advantageous to prevent a part of the radiation  50  emitted by the resistors ( 9 ,  10 ) from diffusing towards the bread  4 . For example, it is advantageous to equip a part of a surface of the reflector  13  with means for preventing the radiation  50  from being reflected towards the bread. In the example represented in  FIG. 1 , it is advantageous that said means are located near the nearest edge  14  from the mobile housing  5 , in order to decrease the quantity of infrared radiation reflected towards the upper and lower parts of the slice  4 . 
         [0045]    This problem is solved by the invention, whose embodiment is represented in  FIG. 2 . More precisely,  FIG. 2  represents a cavalier projection of a heating element  20 , with which is equipped a toaster according to an embodiment of the invention. 
         [0046]    According to the example represented in  FIG. 2 , the heating element  20  comprises a heating resistor  10 , inserted in a tube  11  of quartz. According to another embodiment of the invention, a heating element  20  can be a resistor arranged around a cylinder of ceramic material, or a shielded tubular resistor. 
         [0047]    The tube  11  is surrounded by a reflector  13 , over a sector of 200° approximately. When the element  20  is installed in a toaster  1 , a part  21  of the reflector  13  reflects the infrared rays towards the mobile housing  5 . This substantially plane part  21  is located near an edge  14  of the reflector  13 . 
         [0048]    According to the invention, the part  21  of the reflector  13  is equipped with through holes  22 , which prevent a part of the infrared radiation of the resistor  10  from being reflected towards the housing  5 . 
         [0049]    In the example represented in  FIG. 2 , the holes  22  are arranged in a substantially regular way according to a main axis  23  of the heating element  20 . It is also possible to arrange these holes in an irregular way. For example the holes near a center of the edge  14  can be spaced out more than those near the ends ( 40 ,  41 ) of said edge  14 . Larger holes can also be provided near the ends ( 40 ,  41 ) than near said center. More radiation  50  can thus be reflected towards a center of the section  4  than towards the side edges of said slice. A central part of the slice  4  is better toasted than the edges, which are in general drier at the beginning. 
         [0050]    In the example represented in  FIG. 2 , the holes  22  are arranged in a substantially regular way on axes ( 24 ,  25 ) substantially parallel to the main axis  23  of the heating element  20 . Preferentially, the holes  22  are arranged on at least two axes ( 24 ,  25 ). It is possible to modulate the quantity of reflected radiation by providing holes of different sizes on the axis  24  and the axis  25 . 
         [0051]    In an advantageous way, in order to homogenize the reflection of the infrared radiation, the holes on an axis  24  are arranged in an alternating way relative to the holes on a contiguous axis  25 . 
         [0052]    According to an embodiment of the invention, the holes  22  on the same axis  24  or  25  are of similar size and shape, so as to contribute to a homogeneous radiation over the length  26  of the reflector  13 . 
         [0053]    As previously mentioned, it is also possible to provide holes of variable size and/or shape along the axis  23 , in order to generate a variable radiation over the length  26  of the reflector  13 . 
         [0054]    According to a variant of the invention, it is possible to replace the holes  22  by keys of a non-reflective material, such as paint or varnish. It is also possible to replace the holes  22  by surface zones which have been treated in a particular way, for example frosted zones. 
         [0055]    In addition to the regulation effect for the radiation, the presence of holes  22  or keys of paint on the reflectors also has an esthetic effect. With a “mosaic” aspect for the eye of the user, it diverts his attention from possible traces of calcination. These traces would be much more visible on a reflector with a plain surface. This effect is in particular nice in the case of a toaster comprising transparent walls ( 6 ,  7 ). 
         [0056]    For elements  20  to be installed in the lower part of a toaster box  2 , the presence of holes  22  enables moreover the passage of bread crumbs that have fallen into the reflector  13 . These crumbs are thus prevented from being calcined in contact with the tubes  11  of quartz. However, only the crumbs whose dimensions are lower than those of the holes  22  are likely to pass through said holes  22 . 
         [0057]      FIG. 3  represents a cavalier projection of a heating element  20  according to another embodiment of the invention. This element  20  is similar to that represented in  FIG. 2 . 
         [0058]    In the example represented in  FIG. 3 , the heating element  20  is equipped with a grid  27 , arranged between the tube  11  and the mobile housing  5 . This grid  27  primarily consists of wires  28  extending in planes perpendicular to the main axis  23  of the element  20 . Each end ( 29 ,  30 ) of each wire  28  is in contact with a part of the reflector  13 , or near said reflector  13 . 
         [0059]    The wires  28  are integrally fixed to at least one wire  31 , substantially parallel to the axis  23 , which ensures the cohesion of the grid  27 . 
         [0060]    The wires  28  are bent and surround the tube  11  approximately over a sector of 160°. Thus, in a plane perpendicular to the axis  23 , the tube  11  of the element  20  is entirely surrounded by the unit grid  27 /reflector  13 . 
         [0061]    The section, the number and the arrangement of the wires  28  enable to modulate the intensity of the infrared radiation diffused towards the bread by the resistor  10 , in a direction parallel to the axis  23 . In the same way, the section, the number and the arrangement of the wires  31  enable to modulate the intensity of the radiation diffused towards the bread, in a direction perpendicular to the axis  23 . 
         [0062]    The wires ( 28 ,  31 ) can also have a variable section over their length. 
         [0063]    In a preferential way, the wires ( 28 ,  31 ) are made of metal. They can also be made of another material, having for example a higher absorbance for the infrared radiation. 
         [0064]    In addition to its regulation effect for the radiation, the grid  27  enables to prevent big bread crumbs from falling onto the tube  11  and into the reflector  13 , as well as these crumbs from being carbonized in contact with the tube  11 . More precisely, the bread crumbs whose at least one dimension is larger than a space  32  between two wires  28  can slide on said wires and fall to the bottom of the box  2 . 
         [0065]    The crumbs whose dimensions are smaller than the space  32  between two wires  28  pass between said wires and fall onto the tube  11  or into the reflector  13 . A part of these crumbs can then pass through the holes  22  and fall to the bottom of the box  2 . 
         [0066]    There is however crumbs of an intermediate size, small enough to go through the grid  27  but too big to pass through the holes  22 . 
         [0067]    In order to solve this problem, it is possible to replace the grid  27  by a wall, in particular not perforated, made of a material enabling the passage of at least one part of the infrared radiation emitted by the resistor of the element  20 . A PTFE or mica wall can particularly be used. Such a wall can have a bent shape, similar to the shape of the grid  27 .