Device for cleaning the cooking chamber of a food preparation oven by pyrolysis

Abstract: A food preparation oven comprises a cooking chamber (1) in which means (12) are provided for generating heat waves and for directing them in a suitably concentrated manner onto the surfaces (6, 7, 8, 9, 10, 11) of the walls of said chamber (1); said means (12) are removably arranged in the cooking chamber (1) and are mobile therein so as to direct said heat waves onto the entire surface of said walls (2, 3, 4, 5), said concentrated waves scanning said surfaces (6, 7, 8, 9, 10, 11) but covering only portions of them at any given time, so as to obtain only in and around said portions a high temperature such as to result in the pyrolysis of the impurities which have been deposited on said surfaces (6, 7, 8, 9, 10, 11) during the use of the oven. Said heat waves can also be used for food preparation.

Description: This invention relates to an oven of any type, ie gas, microwave, electric, combination etc., provided with a cooking chamber for food preparation. The problem of cleaning the cooking chamber walls on which substances generated by the food during its cooking, and in particular fats, deposit following use of the oven is well known. This cleaning can be done in various ways, either manually or more particularly by the pyrolysis of such impurities in known manner. With reference to this later method of cleaning the oven cooking chamber, said pyrolysis is achieved by arranging electrical resistance elements at the walls of said chamber to heat the surfaces of said walls (on which said impurities have deposited) to a temperature of around 500°C or more. Pyrolysis effected in this manner has various drawbacks. One of these is the arranging of the resistance elements along the cooking chamber walls, resulting in a higher oven cost, greater difficulties in its construction due to the need to better insulate its walls (for example to prevent them reaching temperatures which are too high and thus dangerous for the user) and greater energy consumption due to the use of such resistance elements. In addition the pyrolysis is achieved by unselectively heating the entire inner surfaces of the cooking chamber walls, even in regions in which this heating is unnecessary, with further energy wastage. A further drawback is that as a consequence of the generalized heating of the inner surfaces of the cooking chamber, these have a very high cooling time which makes it impossible to use the oven for a long time after it has been cleaned by pyrolysis. An object of the present invention is to provide an oven which can be cleaned by pyrolysis without the aforesaid drawbacks. A particular object is to provide an oven in which said pyrolysis can be achieved without arranging resistance elements in positions corresponding with the cooking chamber walls. A further object is to provide an oven of the aforesaid type which can be used soon after it has been cleaned by pyrolysis. A further object is to provide an oven in which said means for effecting pyrolysis on the inner surfaces of the cooking chamber can be used for food preparation. A further object is to provide an oven with a pyrolysis-cleanable cooking chamber which is of smaller weight and dimensions than similar ovens of the state of the art. These and further objects which will be apparent to the expert of the art are attained by a food preparation oven comprising a cooking chamber, characterised by comprising means in this latter for generating heat waves and for directing them in a suitably concentrated manner onto the inner surfaces of the walls of said chamber, said means being removably arranged in the cooking chamber and being mobile therein so as to direct said heat waves onto the entire surface of said walls, said concentrated waves scanning said surfaces in such a manner as to obtain a high temperature thereon which results in the pyrolysis of the impurities which have been deposited on said surfaces during the use of the oven. The present invention will be more apparent from the accompanying drawing, which is provided by way of non-limiting example and in which: Figure 1 is a schematic transparent perspective view of a cooking chamber in an oven constructed in accordance with the present invention; Figure 2 is a perspective view of a part of the oven according to the invention; Figure 3 is a section on the line III-III of Figure 2; Figures 4 and 5 are cross-sectional schematic views of two different embodiments of the part shown in Figure 2; Figure 6 is a view similar to that of Figure 1, illustrating a modified embodiment of the oven of that figure, with some parts shown in partial section. With reference to Figures 1 to 3, the oven according to the invention comprises a cooking chamber 1 provided with walls 2, 3, 4 and 5. Said walls define and delimit the inner surfaces of the chamber 1, namely two lateral surfaces 6 and 7, an end surface 8, a front surface 9, a base surface 10 and a roof 11. According to the invention the oven comprises within the cooking chamber 1 a device 12 which can be removably inserted into said chamber to enable the inner surfaces 6, 7, 8, 9, 10 and 11 of said chamber to be cleaned by pyrolysis. In an embodiment shown in the accompanying figures said device is arranged in a position corresponding with the roof 11 of the chamber 1, and comprises an element 13 arranged to generate a light beam, said element being advantageously a halogen lamp, and a reflector element 14 positioned to correspond with the light element or lamp 13. The lamp 13 is supported by members 15 and 16 positioned at the opposing ends of the lamp 13 and also supporting the reflector element 14. Specifically, from the ends 17 and 18 of the lamp 13 there extend respectively two pins 20 and 21 which are arranged to cooperate with corresponding apertures or blind holes 22 and 23 in the members 15 and 16. In these apertures there are inserted usual bearings 24 or other mechanical decoupling members allowing relative movement between the parts and able to support said pins 20 and 21, and to allow the reflector element 14 to move relative to the lamp 13 in the described embodiment. In the aperture 22 there is inserted an elastic element (compression spring) 25 which acts at one end against the end 22A of the aperture 22 and at its free end carries a usual electrical contact element to enable electrical power to be fed to the lamp 13. The contact element 26 is connected to electrical connectors (not shown) which are connected to a power line (not shown) present in the oven under consideration, via an end support element 27 to which the member 15 is connected, and via the member 15 itself. Specifically, this latter comprises an end projecting part 28 which cooperates with an aperture 29 in the support member 27, at which bearings 30 are provided. The projecting part 28 carries electrical contacts (male) of the quick connection type (for example of plug-in type) cooperating with corresponding counter-contacts (female) connected to electrical cables passing through at least one of two arms 31, 32 which extend from the member 27 to support at one of its ends 33 the device 12. The arms 31, 32 are elastically approachable (arrows F and G in Figure 2) and have bent ends 34 which cooperate with seats 35 provided in the roof 11 of the chamber 1. At the end of at least one of said arms 31, 32 there are provided electrical connectors (not shown) which are connected to the cables passing through the arms for connection, for example by plugging in, to corresponding contacts (not shown) provided in the seats 35. It should be noted that the connection for the electrical power to the lamp 13 is shown (see Figure 3) only schematically, as a dashed straight line 26A in said figure. The reflector element 14 is supported and kept at a short distance from the lamp 13 by arms 40 and 41 fixed to said members 15 and 16. The latter member 16 is close to the wall 3 of the chamber 1 and comprises a projection 42 directed towards the end surface 8 of said chamber. In the illustrated example, the projection 42 is of square cross-section and is arranged to cooperate with a corresponding hole 43 provided in the output shaft 44 of an electric motor 45. This electric motor is advantageously of the stepping type and rotationally moves the reflector element 14 about the lamp 13. This movement is therefore discrete and comprises an alternation of time periods in which the element 14 rotates about the lamp and periods in which the element is at rest. The rotation takes place each time through a very few degrees, the time for which the element 14 remains at rest (halt time) being such as to enable a light beam emitted by the lamp 13 to effect pyrolysis on the walls of the chamber 1. In this respect, it will be assumed that after the oven has been used it is required to clean the inner surfaces of its cooking chamber 1. To achieve this, said device 12 is inserted into the chamber. During this insertion the projection 42 on the member 16 is positioned so that it fits into the shaft 44 of the motor 45. Having done this, the arms 31 and 32 are are forced together in accordance with the arrows F and G of Figure 2 and their free ends are inserted into the seats 35 present in the roof 11 of said chamber. At this point the device 12 has been inserted into the cooking chamber 1 and can be used for pyrolysis of the impurities deposited on the inner surfaces of said cooking chamber 1 during food preparation. By operating a suitable actuator element (such as a pushbutton on the front of the oven), the motor 4 is operated. At the same time (if this is not done directly by operating said pushbutton) the lamp 13 is lit by a suitable pushbutton again in a suitable position on the outside of the oven (for example on the front). Following this, the element 14 begins to rotate about the lamp 13 (which remains fixed), the light beam emitted by the lamp being reflected by said element and suitably concentrated thereby. An example of how this happens is shown in Figure 4. In this figure the reflector element 14 (which is also able to concentrate the light beam onto an inner surface of the cooking chamber ) consists of a paraboloid. In this figure (in which parts corresponding to those of the previously described figures have the same reference numerals), the light beam is by way of example fed in the form of a line (or very narrow band) of light onto the base 10 of the chamber 1. This beam is defined by the end rays K and Z. Said rays are emitted specifically by a lamp 13 screened lowerly by a reflecting film associated with its outer casing. The rays K and Z are therefore directed towards the element or paraboloid 14 and are reflected and concentrated by this onto said base 10. In contrast, in Figure 1 the emitted light beam defines on the wall 10 a light band W which also moves along the lateral walls 6 and 7 (in which it is shown in hatching on the wall 6). With the discrete movement of the element 14, the band W (or the line of Figure 4) moves along said walls and after each individual movement stops for a suitable time during which the temperature of the surface portion covered by the light beam reaches a temperature close to or exceeding 500°C. This temperature results in pyrolysis of the impurities present in said portion. It should be noted that said temperature is reached in the region covered by the light beam (or rather the band W) and in the adjoining regions. However the more distant regions are not subjected to high temperature heating and this enables them to cool rapidly (possibly aided by circulation of air grazing the surfaces of the walls of the chamber 2). In the described embodiment shown in Figures 1 to 4 the device 12 enables pyrolysis to be effected particularly over the surfaces 6, 7, 10 of the walls of the cooking chamber 1. However particular forms of the reflector element 14 can be provided as can particular positions of the device 12 within the cooking chamber (such as in the "spit-roasting" position so that simultaneously with the rotation of the element 14, with or without joint rotation of the lamp 13, the light beam strikes all surfaces of the walls of said chamber. In this manner pyrolysis on all said surfaces is obtained by a single "stepwise" rotation. In contrast, in the described case the element 12 has to be moved from the position shown for example in Figure 1 to a second position substantially perpendicular to this latter. When in this second position the device 12 is again "activated" to also achieve pyrolysis on the surfaces 9 and 8 (and 10 and 11 as in the first position) of the chamber 1. In this second position there will again be provided the means for connection to the motor 45 (or to another motor) and the means for cooperation with the arms 31 and 32 of the member 27. A further embodiment is shown in Figure 5 in which parts corresponding to those of the already described figures are indicated by the same reference numerals. The difference between said embodiment and that already described is in the provision of a reflector 73 positioned below the lamp 13 and associated with this latter in any known manner, and in the provision of a converging lens 74 positioned below the device 12. The use of the invention as shown in Figure 5 is similar to that already described and will not be repeated. It should merely be noted that the element 14 generates a light beam of parallel rays which are then converged by the lens 74 to form a "line" of light (or light band) on a surface of the chamber 1. A further embodiment of the invention is shown in Figure 6, in which parts corresponding to those of the already described figures are indicated by the same reference numerals. This oven embodiment has the device 12, constructed in any of the described forms, positioned above a transparent (glass or similar) element 90 of special shape. This element is of concave shape with its concavity facing the device 12. The element 90 defines two compartments within the cooking chamber 1. The food to be processed is placed in a first compartment 1A and the device 12 is placed in a second compartment 1B. This device is mobile with discrete translational movement above the element 90 and is guided in this translational movement by tracks 91 and 92 formed on portions 8A and 9A of the walls 3 and 5 of the chamber 1. Movement is achieved by known movement means such as a rack and pinion, a belt with drive and return pulley or the like. Because of the particular form of the concave element 90, a single "stepwise" translational movement of the device 12 (which in this case does not comprise the reflector element mobile relative to the lamp 13) a band (or "line") of light is generated over all surfaces of the walls of the cooking chamber, with resultant pyrolysis on all surfaces. It should be noted that the transparent element 90 of Figure 6 and the lens 74 of Figure 5 are constructed of a glass material having high transmittance within the infrared band. An oven has been described provided with a device 12 which generates a light beam. However for the purposes of the invention, ie for achieving pyrolysis on the surfaces of the walls of the chamber 1, the device 12 can alternatively use other known means (laser, microwave or other means) to generate heat waves which generate a very high temperature on said surfaces by striking them. In addition, by combining said device with a voltage or current intensity variator, the device can be used for variable power grilling or for lighting the cooking chamber.

Claims: A food preparation oven comprising a cooking chamber, characterised by comprising means (12) in this latter for generating heat waves and for directing them in a suitably concentrated manner onto the surfaces (6, 7, 8, 9, 10, 11) of the walls of said chamber (1), said means (12) being removably arranged in the cooking chamber (1) and being mobile therein so as to direct said heat waves onto the entire surface of said walls (2, 3, 4, 5), said concentrated waves scanning said surfaces (6, 7, 8, 9, 10, 11) in such a manner as to obtain a high temperature thereon which results in the pyrolysis of the impurities which have been deposited on said surfaces (6, 7, 8, 9, 10, 11) during the use of the oven. An oven as claimed in claim 1, characterised in that the heat wave generation means comprise a generator (13) for said waves and a reflector element (14) positioned to correspond with said generator. An oven as claimed in claim 1, characterised in that the heat wave generator is a light beam source (13), advantageously a halogen lamp. An oven as claimed in claim 1, characterised in that the heat waves are generated by the emission of microwaves by a suitable generator. An oven as claimed in claim 1, characterised in that the heat waves are generated by a laser beam emitted by a suitable generator. An oven as claimed in claims 2 and 3, characterised in that the heat wave generator (13) and the reflector element (14) are mobile relative to each other, said element rotating with continuous or reciprocating motion about the generator (13). An oven as claimed in claim 5, characterised in that the heat wave generator (13) is supported, via mechanical decoupling members such as bearings (24) or the like which allow relative rotation between the parts, by members (15) positioned at the opposing ends (17, 18) of said generator and supporting the reflector element, at least one (16) of said members being connected to an output shaft (44) of a motor means (45), the other member (15) being connected, via mechanical decoupling members such as bearings (24) or the like allowing relative rotation between the parts, to an end support member (27), this latter being provided with elements (31, 32) for fixing a free end (33) of the heat wave generation and reflecting means (12) to the roof (11) of the cooking chamber (1). An oven as claimed in claim 6, characterised in that for its connection to the motor means (45), one (16) of the members (15, 16) supporting the reflector element (14) is provided with a suitably shaped projection (42) arranged to cooperate with a corresponding seat (43) in the output shaft (44) of said motor means (45). An oven as claimed in claim 6, characterised in that the motor means (45) are an electric motor (45) advantageously of the stepping type able to generate a discrete movement of the heat wave emission means (12), said means (12), after every movement, remaining in the position reached for a much longer time period than that through which said movement took place. An oven as claimed in claim 6, characterised in that the elements for fixing a free end (33) of the heat wave generation means (12) to the roof (11) of the cooking chamber (1) are arms (31, 32) which project from the end support member (27) and are provided with ends (34) arranged to cooperate with suitable parts (35) of said roof (11), said arms being advantageously elastically mobile relative to each other. An oven as claimed in claim 2 or 3, characterised in that the heat wave generator (13) and the reflector element (14) are fixed together and are mobile jointly. An oven as claimed in claim 10, characterised in that the joint movement of the heat wave generator (13) and reflector element (14) is a rotary movement. An oven as claimed in claim 10, characterised in that the joint movement of the heat wave generator (13) and reflector element (14) is a translational movement. An oven as claimed in claim 12, characterised in that the translational movement of the reflector element (14) and heat wave generator (13) takes place in a guided manner within a compartment (1B) of the cooking chamber (1) defined by a transparent element (90) positioned within said chamber, said transparent element (90) defining within said chamber (1) a further compartment (1B) which contains the foods during their processing. An oven as claimed in claim 13, characterised in that the translational movement of the heat wave generation means (12) takes place along guide tracks (91, 92) provided on portions (8A, 9A) of walls (8, 9) defining the cooking chamber (1), said movement being provided by motor means coupled to known gear mechanisms and/or linkages. An oven as claimed in claim 13, characterized in that the transparent element has a concave shape with its concavity facing the heat wave generation means (12) and its convexity facing the compartment (1A) in which the foods are processed. An oven as claimed in claim 2, characterised by comprising a further reflecting screen (73) positioned a short distance from the heat wave generator (13), said further screen (73) being symmetrical to the reflector element (14) about said generator (13). An oven as claimed in claim 16, characterised in that a convergent lens (74) is associated with the heat wave generation means (12) in a position close to this latter. An oven as claimed in claims 13 and 18, characterised in that the transparent element (90) and the convergent lens (74) are constructed of a glass material with high transmittance within the infrared band. An oven as claimed in claim 3, characterised in that the light beam generator (13) is screened by a screen positioned within its outer casing. An oven as claimed in claim 2, characterised in that the reflector element is a paraboloid. An oven as claimed in claim 1, characterised in that the heat wave generation means (12) are used for food preparation and in particular for grilling, said means being connected for this purpose to a voltage or current intensity variator. An oven as claimed in claim 1, characterised in that the generated heat waves cover limited portions of the surfaces (6, 7, 8, 9, 10, 11) of the walls (2, 3, 4, 5) of the cooking chamber (1) at any given time.

Inventors: FRANZETTI GIOVANNI, MONTANARI CARLO, FRANZETTI, GIOVANNI, MONTANARI, CARLO
Applicants: EURODOMESTICI IND RIUNITE, WHIRLPOOL EUROP, IRE INDUSTRIE RIUNITE EURODOMESTICI S.R.L., WHIRLPOOL EUROPE B.V.
Application year: 1991
Main classification: F24C7
IPC codes: F24C14