MXPA97010355A - Appliance for heating with microon - Google Patents

Abstract

The present invention is directed to offering a microwave heating apparatus which heats varieties of heating objects, without affecting the excellent property, by introducing an accessory to control the environment surrounding the heating object. To implement the objective, the heating apparatus comprises a heating cavity for receiving a heating object, a microwave generating accessory for irradiating microwaves for heating purposes, a steam generating accessory for supplying steam to the cavity of the body. heating, and a control accessory to control the microwave generation accessory and the steam generation accessory, so that the internal temperature and the surface temperature of the heating object are approximately equal

Description

APPARATUS FOR HEATING WITH MICROWAVE FIELD OF THE INVENTION The present invention is related to a microwave heating apparatus, for ca 1 in t / r to a variety of objects in a suitable environment.

BACKGROUND OF THE INVENTION As a microwave heating apparatus of the prior art, a furnace for freezing foodstuffs is well known, as described in Japanese Patent Publication No. Sho55-51541. In the following, the constitution of the furnace is described with reference to Fig. 23. Referring to Fig. 23, a prior art furnace for des freezing / cooking, comprises a mixer 3, placed on the roof 2 of the body, 1, of a mechanically closed oven and a magnetron irradiation orifice, 4, placed near the mixer. Inside the furnace body, 1, a removable shelf, 5, is provided for the food; underneath it there is provided a tray, for liquids, removable, 6, for water, oil, etc., in which a food product A can be submerged, when necessary; In addition, a heating medium 7 is provided under the tray.

REF: 26373 for gas, electricity, etc. Through a combined work of the magnetron irradiation orifice, 4, the liquid tray, 6, and the heating means, 7, a heating object is heated with the irradiation of magnetrons from the top and at the same time time, depending on the needs, with steam from the boiling water, which is obtained from the bottom. Through the combined use of magnetron irradiation and steam heating, the time for passage through the zone of maximum ice crystal formation is minimized, during which the cell wall is damaged when a frozen food product is thawed , and the food product is defrosted uniformly, without allowing its delicious content to escape. Because water vapor is available, the oven can also be used to thaw frozen breads / frozen cakes, or to treat the stages of the whole bread / cake process with fermentation. In addition to steam heating, the oven is capable of conducting several heating / cooking processes. For example, the unfreezing of pre-processed, frozen, fat-containing food products provided in the liquid tray is described; the thawing of a package of frozen food by the combined use of magnetron and hot air irradiation, of a heating appliance (hot air mixed by the mixer placed on the ceiling), and other cooking methods. However, in a microwave heating apparatus of the prior art, because the atmosphere in the heating chamber is of a temperature of about 100 ° C / 100% humidity, it has many drawbacks such as: when a baked bread, frozen, or a tempura (Japanese dish with cooked vegetables and seafood) fried, frozen, the surface becomes sticky with steam, which affects the deliciousness of the food; a non-uniform distribution of the temperature between the interior and the surface of a prepared food is easily originated, which, in the case of thawed frozen breads, where the water content is low, damages the food affecting the flavor, the elasticity or the sensation in the teeth. The article is now explained in more detail. Figure 24 illustrates the temperature change of a prepared food and the oven cavity in a prior art oven, where the heating with the microwaves and the heating with the steam are carried out at the same time. The temperature of a prepared food, starting with the freezing temperature (-20 ° C), rises, passing through the area of maximum ice crystal formation (-1 ° C to -5 ° C), where large quantities are consumed of energy, taking a little time there. While the prepared food remains in the frozen state, it does not absorb the microwaves efficiently, instead, the microwaves are introduced deep into the prepared food and the heat is conducted quickly. As a consequence, the temperature inside a prepared food is relatively uniform. The application of steam helps the prepared food pass quickly through the area of maximum ice crystal formation, but the temperature inside the heating cavity ll.e to be about 100 ° C and the humidity can also be about 100% After passing through the zone of maximum ice crystal formation, a prepared food carries with it those places that have already been thawed and those still frozen. The thawed parts show a dielectric loss from several times to several tens of times higher, and the microwaves are selectively absorbed, which creates a non-uniform temperature within the prepared food. Especially when steam is applied, the surface of a prepared food accumulates steam and only a surface area of the prepared food is heated with microwaves, which initiates the increase in surface temperature. That is, when the internal temperature of a prepared food reaches an optimum level, the surface temperature is already much higher than optimal. The optimum temperature for a food is different, depending on the type; is greater than 80 ° C, for, for example, steam-treated foods; from 60 ° C to 70 ° C for the tempuras, if it is too hot, the food material becomes dehydrated and the moisture is deprived by the coating and the flavor is affected. The optimum temperature for the loaves is the ambient temperature, or a temperature slightly higher than the body temperature; If it is too high the material is damaged, and the taste, elasticity and sensation in the teeth are affected. In any case, the optimum temperature is at least below 90 ° C. Also, optimum moisture is different for each food, depending on the type. For example, the taste deteriorates with the loaves and tempuras if their surface gets wet. As described above, in a microwave heating apparatus of the prior art, emphasis has been placed on how fast a heating object passes through the zone of maximum ice crystal formation, while little attention was paid on how to prepare a prepared food in an environment that is ideal for the prepared food. That is, when the steam is provided, the environment in the heating cavity is always at a temperature of almost 100 ° C and approximately 100% humidity, therefore, a prepared food has never been ca / cooked in an optimal environment.

DESCRIPTION OF THE INVENTION The present invention is directed to the resolution of the drawbacks described above and aims to heat / coke varieties of heating objects to an excellent condition by introducing a means to adequately control, for example, temperature, humidity, the mode of air flow, etc. According to the present invention described, a means is introduced for the control of the environment surrounding a prepared food, or other heating object, for the control of the atmosphere inside a heating cavity, so that it is almost identical to the temperature, humidity, etc., which are ideal for the ca entam ent / cooking of a prepared food. By doing so, the surface temperature and the internal temperature of a prepared food remain almost the same, therefore, a prepared food that is under the heating process, is not deprived of, nor is it supplied too much heat or humidity, which allows the cal ent ent enti / cocci ón is made in a more suitable environment. To implement an even better heating operation, a method according to the present invention varies the output of the microwaves according to the condition of the heating object during heating, to control the profile of the temperature increase of the heating object. By doing this, the condition of a prepared food, or a heating object, is adapted to the environment within the heating cavity, and a prepared food is heated to a suitable temperature, without losing much moisture. Furthermore, according to the present invention, the heating atmosphere, of the heating cavity, is directly monitored to be returned to a control means. This ensures reliable control of the environment within the heating cavity.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 illustrates a method for controlling the environment within the heating cavity of a microwave heating appliance, according to a first embodiment. Figure 2 shows the appearance of a microwave heating apparatus, according to the present invention. Figure 3 shows a front view, in cross section, of a microwave heating apparatus, according to a first embodiment of the present invention. Figure 4 is a block diagram showing the constitution for controlling the environment within the heating cavity of. a microwave heating apparatus, according to a first mode. Figure 5 shows a front view, in cross section, of a microwave heating cavity, according to a second embodiment. Figure 6 shows a method for controlling the environment within the heating cavity of a microwave heating apparatus, according to a third embodiment. Figure 7 shows a method for controlling the environment, within the heating cavity, of a microwave heating apparatus, according to a fourth embodiment. Figure 8 shows a front view, in cross section, of a microwave heating cavity, according to any of the third or fourth embodiment. Figure 9 shows a front view, in cross section, of another microwave heating cavity, according to any of the third or fourth modes. Figure 10 is a block diagram showing the constitution for controlling the environment within the heating cavity of a microwave heating apparatus, according to any of the third or fourth modes. Figure 11 shows a method for controlling the environment within the heating cavity of a microwave heating apparatus, according to a fifth embodiment. Figure 12 shows a method for controlling the environment within the heating cavity, of a microwave heating apparatus, according to a sixth embodiment. Figure 13 shows a method for controlling the environment within the heating cavity of a microwave heating apparatus, according to a seventh embodiment. Figure 14 shows a front view, in cross section, of a microwave heating cavity, according to an eighth embodiment. Figure 15 shows a front view, in cross section, of a microwave heating cavity, according to a ninth embodiment. Figure 16 shows a front view, in cross section, of a microwave heating cavity, according to a tenth embodiment. Figure 17 shows a method for controlling the environment within a heating cavity, of a microwave heating apparatus, according to a tenth embodiment. Figure 18 shows a method for controlling the environment within a heating cavity, of a microwave heating apparatus, according to an eleventh embodiment. Figure 19 shows a method for controlling the environment within a heating cavity, of a microwave heating apparatus, according to a twelfth embodiment. Figure 20 shows a method for controlling the environment within a heating cavity, of a microwave heating apparatus, according to a thirteenth embodiment. Figure 21 shows a method for controlling the environment within a heating cavity, of a microwave heating apparatus, according to a fourteenth embodiment. Figure 22 shows a front view, in cross section, of a microwave heating apparatus, according to a fifth category. Figure 23 shows a front view, in cross section, of a heating cavity, of a freezing oven 1/2 / cooking, of the prior art. Figure 24 shows a method for controlling the environment within a heating cavity of a freezing / cooking oven of the prior art.

BEST MODE FOR CARRYING OUT THE INVENTION (mode 1) A first embodiment of the present invention is described below, with reference to the Figures.

Figure 2 shows the appearance of a heating appliance that implements a method for heating a food product, according to the present invention. In the front part of the body of the oven, 8, there is a door 9 positioned so that it can be opened by means of a joint, to close the heating cavity in which a food product is to be housed. On an operation board, 10, a keyboard for the heating instructions, 11, or an input means for inputting instructions to a control section that will be described later; the instructions are comprised by a one-digit or two-digit code, which corresponds to factors such as the category and quantity of the food product, storage temperature (frozen or cooled), final heating temperature, etc., which are relevant to the method of heating. A water tank, 12, removable, is placed on the right side of the body. Figure 3 shows a front view, in cross section, of a heating cavity; a means of generating magnetrons or microwaves, 24, for irradiating microwaves, and a steam generator, 15, for generating steam, are coupled with the heating cavity 13. The magnetron generator and the steam generator are controlled by a control section, 21, the operation of which is described later. The steam generator 15 comprises a boiler, 16, an atomizer, 17, which comprises an ultrasonic vibrator, and a temperature control of the heater 18, and converts the water fed from the water tank 12 to the boiler 16, into small particles of water, in the atomizer 17, and the temperature control of the heater heats the small particles of water to a specified temperature. Under the controlled operation of the atomizer 17 and the controlled input to the temperature control of the heater 18, the steam generator 15 produces an air with a desired temperature and humidity. A food product 19 is placed in a tray 20, which has several holes or slots. Figure 4 is a block diagram showing a constitution of the control system; the control section 21, or some means for controlling the environment, reads a designated heating condition, of a memory 22, after receiving an instruction that was input to the keypad for the heating instructions, 11. The control data for the steam generator 15, viz., control data of the operation of the atomizer 17 and input control of the temperature control of the heater 18, and the data of the power supply conditions to the magnetron 14, are stored as the conditions of heating. This data can be either a sequential time control value, for each respective block, or a certain mathematical formula. In a case where this is a mathematical formula, the control section 21 performs an operation to obtain the sequential time data and the energy supplies to the atomizer 17; the temperature control of the heater, 18, and the magnetron, 14, are controlled according to the sequential time data; consequently, the temperature / humidity of the steam to be fed to the heating cavity, as well as the temperature of the food product, are controlled in a manner already designated, together with the progress of the heating process. In Figure 1, which illustrates the present invention, (a) shows the temperature within the heating cavity and the temperature of the food product during the heating process; (b) the transition of the moisture within the heating cavity; and (c) the output of the microwaves. What is important with the present invention, is that even when the steam generation means are put into operation and that the heating is carried out with steam, the environment inside the heating cavity is not fixed in a constant state of about 100 ° C of turbulent temperature. a / approximately 100% humidity. In other words, because the control section, 21, controls the output of the microwaves and the steam generator, an apparatus, in accordance with the present invention, cooks the food product always under a more suitable environment for the food product. . A practical heating method is now described. As indicated in (a), the temperature of a food product started from the freezing temperature (-20 ° C), passes through the zone of maximum ice crystal formation (-1 ° C to -5 ° C), taking a certain time lapse (point A). Because the food product absorbs microwaves only slightly and has a good internal heat conduction, the microwave is generated at its maximum power to be irradiated to the food product during the first half of the heating; and then, in the second half, when part of the food product begins to melt, the outlet is decreased to an adequate level, as shown in (c). During the previous period of freezing, the temperature inside the heating cavity is maintained at, or slightly above, the ambient temperature, and the humidity, at normal or slightly higher humidity, as shown. in (b). That is, freezing is mainly conducted with microwaves, which penetrate deeply into a food product, in the frozen state, while the use of steam is suppressed. After passing point A, the food product, in which a molten part and a frozen part coexist, begins to absorb microwaves significantly. As described above, the molten part (water) shows a dielectric loss, from several times to several tens of times greater than that of the frozen part, therefore, the output of the microwaves is reduced to a level of approximately one fifth or one sixth of the total power, as shown in (c). The temperature and humidity, within the heating cavity, are increased after point A, or its neighborhood, as shown in (a) and in (b). When controlling the temperature of the heating cavity, together with the progress of the heating process, to maintain an almost identical temperature almost identical to that of the food product. Because the thermal capacity of the air is low and the food product is heated quickly with microwaves, it is efficient to set the room temperature slightly higher, as shown in the Figure. After receiving a code, entered from the instruction keyboard for heating, the control section searches for the memory and reads the control data corresponding to the category and quantity of the food product, storage temperature (frozen or cold, etc.) , temperature of the final heating, and other points; and executes the control, from time to time, in the steam generator and in the magnetron generator, according to these control data. In order to provide a heating object, after having been defrosted with moisture, an adequate steam is supplied from the steam generator, taking into consideration the humidity of freshly baked bread. Accordingly, according to the present invention, a food product is not heated in an environment, temperature of about 100 ° C / humidity of about 100%, when hot steam is provided, conditions under which the prior art carried out the heating. Through the execution of these controls, the difference between the food product itself and the environment that surrounds it, is reduced to a minimum, a situation under which it is difficult to establish the exchange of temperature and humidity (water). That is, when an average temperature in the center of the food product reaches an adequate level, the temperature of the environment is also almost at the same level; therefore, it is difficult to carry out heat exchange and moisture transfer on the surface of the food product. As a consequence, a bread, an ideal temperature of which is the ambient temperature or a temperature slightly higher than the temperature thereof, does not present any material damage to the food product, due to the very small difference of the internal / external temperature; and a frozen bread can be defrosted, maintaining the same flavor and elasticity that it had when it was just baked and that was preserved until just before being frozen, to an excellent condition, and the sensation to the teeth is comparable to the state it had just when baked. As a result, the process of ca 1 in t ami in t / cocc ón proceeds maintaining the surface temperature and the interior temperature, of a food product, approximately equal, as shown in Figure 1. Because moisture within the heating cavity is optimized by taking into consideration the moisture content of a freshly baked loaf, the crust (outer layer) of bread does not absorb excessive moisture from the steam. In the case of tempura (Japanese dish with cooked vegetables and marine food), because at the time when the temperature inside the object reaches the temperature of 60 ° C to 70 ° C, the coating is also heated At approximately the same temperature, the interior of the object is not deprived of moisture by the coating and maintains its juicy state. In the present embodiment, the surface of both the bread and the tempura is somewhat wetter when the heating is finished, due to the influence of the steam, but it dries to toast in several minutes, before the dishes are brought to the table . In repeated experiments, those by the present modality produced a more roasting state in several minutes after the heating was finished, compared with those heated using only microwaves. The reason seems to be that: when a hot food product is extracted from the heating cavity to a normal environment, where it is dry and at low temperature, it loses heat and humidity, thus providing, in advance, a light moisture that corresponds with an amount that is lost on the surface of the food product, it recovers a freshly cooked state in several minutes. On the other hand, those heated only with microwaves became increasingly wet in their coating, after finishing their heating. The reason seems to be that: because the temperature of the interior of the object is greater than that of the coating, the humidity inside the object moves towards the coating, causing the coating to be wet, and the interior of the object undergoes dehydration. (mode 2) Figure 5 is a front view, in cross section, showing a heating cavity according to a second embodiment. In the first mode, the heating work is carried out, after receiving a heating instruction entered through the input means, according to the heating conditions registered in advance in a memory. However, the environment of a food product that is under a heating process can be better controlled with greater precision by providing a detection means for measuring the environment within the heating cavity and giving feedback to the energy supply of the steam generator. In the heating cavity 13, a temperature sensor 23 and a humidity sensor 24 are placed as environment detection means. The temperature and humidity within the heating cavity, 13, are detected and sent to a control section 21. This allows the control section to accurately monitor the environment inside the heating cavity, and see if it is found. under good control, or if it is deviating. In a case when the environment within the heating cavity deviates from a specification, the energy input to the steam generator 15 is varied to restore the environment to the specification. In the present embodiment, both temperature and humidity are detected to make the control safe. However, because a vague idea of the amount of steam generation can be conceived by the supply of energy to a steam generator, the environment within the heating cavity can be monitored practically only by means of detection Of temperature. (mode 3) Now, in the following, a modality with an accessory for blowing air is described. Figure 8 shows a constitution containing an accessory for blowing air; where a fan 25, or an accessory for blowing air, cools the magnetron 14 and other components, and then carries a certain amount of the air flow into the heating cavity, 13, guided by an air guide, 26. This ventilation of air agitates the non-uniform vapor within the heating cavity and discharges the excess steam out of the housing, through an outlet guide, 27, and an outlet hole, 28, placed in a part of the housing. . As described above, the fan 25 mixes the air produced in the steam generator 15, at a desired temperature and humidity, with outside air, allowing adjustment of the environment within the heating cavity on a faster scale and more wide. In addition, the flow of air within the heating cavity makes it easier to control the dryness on the surface of the food product. The food product 19, a heating object, is placed in a tray 20, which has a substantial number of small holes or slots. Figure 9 is a front view, in cross section, of a heating cavity, according to another form of the embodiment. In the heating cavity 13, a circulation fan 29 is placed in place of a fan provided as the accessory for blowing air in the embodiment just described. Although it is impossible, for the circulation fan 29, to adjust the temperature and humidity of the air that is discharged from the steam generator 15, with a controlled temperature / humidity in a faster and wider mode than the fan described in the previous one. mode of the modality, the circulation fan works effectively to improve the uniformity of temperature and humidity, by stirring the air inside the heating cavity, while maintaining the temperature and humidity, once adjusted, inside the cavity of heating, 13. In addition, the dryness on the surface of the food product can be easily controlled by controlling the speed and volume of the air flow. Figure 10 is a block diagram showing a control system; where a control section, 21, receives a heating instruction code entered on the keypad for heating instruction, 11, and reads the corresponding heating conditions of a memory, 22, which is the storage medium. As heating conditions, the control data of the steam generator, 15, viz., The data to control the operation of the atomizer, 17, and the data to control the input to the temperature control of the heater, 18, the data that show the conditions of the power supply to the magnetron, 14, and the control data of the fan 25, or an accessory for blowing air, are stored in the memory. This data can be found either in the form of sequential control data, for each respective block, or in the form of a mathematical formula. The control section, 21, controls, according to the sequential data of time, collected from the memory, or the sequential data of time, obtained as a result of the operation of a formula, the supply of energy to the atomizer 17, the control of temperature of the heater 18, and the magnetron 14, as well as the operation of the fan 25, to control the temperature and humidity of the steam to be introduced into the heating cavity, at each stage of the heating process, and the flow of air and the temperature of the food product at predetermined conditions. Figure 6 shows a method for controlling the environment with the constitution described above. Where (a) shows the temperature within the heating cavity and the temperature of the food product under the heating process, (b) the transition of the moisture within the heating cavity, (c) the microwave output, and ( d) operation of the air flow fan. In (a), the temperature of a food product started from the freezing temperature (-20 ° C), passes through the zone of maximum ice crystal formation (-1 ° C to -5 ° C), taking a certain period of time (point A). Because the food product absorbs microwaves only slightly and has good internal heat conduction, the microwave is generated at full power to be irradiated to the food product during the first half of the heating process, and then, in the second half, When part of the food product begins to melt, the outlet is decreased to a suitable level, as shown in (c). During the previous freezing period, the temperature inside the heating cavity is maintained at room temperature, or slightly higher than that, and the humidity at a normal or slightly higher humidity, as shown in ( b) That is to say, the freezing is mainly conducted by microwaves, which reach a deep level in a food product in a frozen state, while the use of steam is suppressed. After passing through point A, the food product, in which the melted part and the frozen part coexist, begins to absorb the microwave significantly. As described above, the melted part (water) shows a dielectric loss from several times, up to several tens of times, higher than the frozen part, therefore the output of the microwave is reduced to a level of approximately one fifth or one sixth of the total power, as shown in (c). The temperature and humidity inside the heating cavity are elevated after point A, or its vicinity, as shown in (a) and (b). When the temperature is controlled within the heating cavity, together with the progress of the heating process, to maintain a temperature almost identical to that of the food product. The control section searches the memory, after receiving a code entered from the instruction keyboard, and reads the control data corresponding to the category and quantity of the food product, the storage temperature (frozen or cooled, etc.), the final heating temperature, and other items; and execute control, from time to time, on the steam generator, the magnetron, and the air blower, according to these control data. Through the execution of these controls, the difference between the food product itself and the environment around it is reduced to a minimum, a situation under which it is difficult to exchange temperature and humidity (water). That is, when the average temperature in the center of the food product reaches an adequate level (point B), the ambient temperature is also at an almost equal level, therefore, it is difficult to carry out the heat exchange and the Moisture transfer, on the surface of the food product. As a consequence, a bread, where an ideal temperature for the same is the ambient temperature or a temperature slightly different from the body temperature, does not suffer any material damage to the product, due to the very small difference of the internal / external temperature; and a frozen bread could be defrosted while maintaining the same flavor and elasticity that it had just after being baked, and kept until just before it was frozen, to an excellent condition, and the sensation to the teeth becomes comparable to the state that had just baked. In the case of tempura (Japanese dish with cooked vegetables and marine food), because at the moment when the temperature inside the product reaches a temperature of 60 ° C to 70 ° C, the coating is also heated to approximately same temperature, the interior of the product is not deprived of moisture by the coating, and maintains the juicy state. The surface of both bread and tempura (Japanese dish with cooked vegetables and marine food), at point B, is affected to a certain degree, with respect to its humidity, by the steam. By keeping the blower fan driven even after point B, as shown in (d), excess moisture that is retained on the surface of the food product can be easily removed. Therefore, it is effective for food products, such as coating the tempura (Japanese dish with cooked vegetables and seafood) and the crust of the bread, which need to have a crunchy feel, make the fan work for several minutes after reach point B. It has become clear, after conducting the experiments repeatedly, that the coating that has been heated only with the microwaves, becomes increasingly wet over time, while the heated under a tea atmosphere Controlled humidity / humidity, provides a dry and crisp feeling if the blower fan keeps running for several minutes after reaching point B. This effect, due to the blown air, is called "soft / moderate effect by means of ignition already paid". It seems that, when heated only with microwaves, the internal temperature of the product rises more than that of the coating and, after point B, the humidity inside the product moves towards the coating; in this way the delicious is affected because the coating becomes wetter and the interior of the product is dehydrated.

According to the present invention, a small amount of moisture can be provided in advance, which must be lost during the "smooth / moderate effect by means of turning on and off", after point B, to the surface of a food product; creating, in this way, a state through which a state of the food product more similar to the freshly baked state is reproduced, in several minutes, later. The termination notice is displayed at point C by means of a buzzer, or some other means. The delay time for issuing the notification can be counted from point B, by providing a timer in the control section, or it can be determined by detecting the decrease in temperature within the heating cavity to a certain level, by placing a sensor temperature inside the heating cavity. By delaying the termination notification to point C, a cook can extract the food product from the oven relying entirely on the notification, without thinking of an ideal timing of completion. The delayed notification also contributes to safety, because the temperature and humidity within the cavity fall, if slightly, the same time when the food product is removed from the hob. (mode 4) Now, in the following, another mode of the control method is described, under a constitution comprising an air blowing accessory. Figure 7 illustrates an example of control of the environment within the heating cavity, so that its temperature never exceeds the temperature that the food product has at the time of finishing the calming process. In Figure 7, which illustrates the present invention, (a) shows the temperature within the heating cavity and the temperature of the food product during the heating process, (b) the transition of the moisture within the heating cavity, (c) the output of the microwaves, and (d) the operation of an air blower fan. In (a), the method of control, from the start of heating to point A, is totally the same as that of mode 1. The constitution of the reduction of the output of the microwaves, after point A, to a level of about one fifth or one sixth of the total power, as shown in (c), is also the same as that of mode 1. The air blower fan keeps running intermittently after point B, such as shown in (d), and the food product receives an intermittent puff of air, like the wind of a hand fan; which may make the "soft / moderate effect through on and off" mentioned earlier. That is, when a food product is exposed to a continuous wind blowing, its surface easily creates a non-uniform temperature distribution; but when it is blown with an intermittent wind, the temperature distribution becomes more uniform aided by the thermal conduction inside the food product, making possible a good cooking, with a less irregular temperature distribution. The temperature, as well as the humidity, within the heating cavity rise suddenly after point A, as shown in (a) and (b). The temperature inside the heating cavity is approximately matched to the temperature that the food product should have at the end of the heating process; practically, the temperature of the cavity is set slightly higher. By means of the control method described above, the food product receives, after point A, a more important influence on temperature and humidity, of the surrounding environment, than in the control mode described above, of mode 1, therefore, the heating procedure proceeds more efficiently. However, the environment never goes beyond an adequate temperature level of a food product. Therefore, heating in the low temperature zone, or in the medium temperature zone, for bread, tempura, etc., as well as the heating of delicate items, which must be strictly protected from moisture, may be carried out. in a gentle manner, as in the method of mode 1. In the present embodiment, no detection means, such as a sensor, is employed, and the heating work proceeds according to predetermined heating conditions, stored in the memory and designated by a heating instruction inputted from the input accessories. However, a detection accessory can, of course, be provided to detect environmental conditions within the heating cavity and input the results as feedback to the energy input for the steam generator. A temperature sensor and a humidity sensor can serve as the detection accessory. In addition, during the time after the end of the heating (point C), until the oven door is opened to extract the food product, the heating cavity can be used as a hot chamber, which keeps the cooked foods warm, without affecting the quality, just by continuing an environmental adjustment. Based on a code entered from the instruction keypad, the control section picks up from the memory the control data of the steam generator and the magnetron, corresponding to the category and quantity of the food product, the start temperature (frozen or cooled, etc.), the final heating temperature, and other data entered, and executes the control, from time to time, according to this data. (mode 5) A fifth modality is described below. Figure 11 illustrates a heating method, according to the present invention, wherein the center and surface temperatures of a food product are increased with relative uniformity. Where (a) shows the temperature within the heating cavity and the temperature of the food product during the heating process; (b) shows the transition of the moisture within the heating cavity; and (c) the microwave output. The temperature and the humidity inside the heating cavity, just before the end of the heating are controlled in such a way that they are a temperature and a humidity, respectively, which are suitable for a food product to be cooked in a suitable manner. Referring to (a), the temperature of the food product, starting from the freezing temperature (-20 ° C), slowly rises to the zone of maximum ice crystal formation (-5 ° C to -1 ° C), therefore the absorption of the microwaves is very small. In the area of maximum ice crystal formation, the energy is consumed to melt the ice, therefore, it takes a little time to pass through the area (point A). After passing point A, the food product begins to absorb microwaves significantly, resulting in an acute increase in the temperature of the food product. Because it takes some time before the temperature and humidity, within the heating cavity, reach a final state level of heating, as shown in (a) and (b), the output of the microwaves (c) it is controlled, depending on the food product, so that the slow-down / cooking process does not end before the setting of the environment is ready. In the case of a food product whose increase in temperature in the center is almost identical to that of the surface, it is not necessary to reduce the output of the microwaves after point A. In this way, the environment inside the heating cavity is adjusted well so that it corresponds with the final state of heating; therefore, a food product is heated gently from the surface with the latent heat of the steam, at the same time with the microwaves. As a consequence, the food product is easily heated with well-balanced temperatures in the center and on the surface, when the process of cooking is completed. In addition, because the moisture on the surface of the food product is well preserved, the boiled rice or pasta does not dry or get wet. (mode 6) The following describes a sixth modality. The Figure 12 shows a heating method, according to the present invention, for heating a food product, where its central part is heated before the surface; where (a) shows the temperature within the heating cavity and the temperature of the food product during the heating process; (b) the transition of the moisture within the heating cavity; and (c) the output of the microwaves. The temperature and humidity, within the heating cavity, are controlled just before the end of the heating, so that they are a temperature and a humidity, respectively, that are suitable for a food product that is to be cooked in a suitable manner. Starting from the freezing temperature (-20 ° C), if a food product is irradiated with microwaves from the beginning, the microwaves go towards the center part and the part of the center is heated first. Therefore, as shown in (a) and (b), the temperature and humidity, within the heating cavity, are adjusted so that they are immediately reaching a level at the end of the heating process; and steam is made to condense on the surface of the food product, taking advantage of the temperature difference between the environment and the food product, and a layer of water is formed by the temperature of the environment. At the moment when the surface of the food product begins to melt (point A), microwave heating is started, as shown in (c). Then, a part of the microwaves, which should have gone towards the center part, is absorbed by the surface of the food product, heating the food product both from the inside, as well as from the outside, in a well-balanced form. As a practical example, a s h or o -ma i is heated homogeneously, avoiding the inconvenience that a s h a or -ma i of tempered temperature, is very hot inside when it is chewed. In addition, the surface of s h a o -ma i is not dry, and it is well preserved with moisture and softness to the preservation of its original delicious flavor. It is also confirmed by means of experiments that the weight reduction, after heating, is lower among those heated according to a method of the present invention, compared to those heated only with microwaves. In the case of shrimp tempura, because the shrimp and the coating are heated to almost the same temperature, the inconvenience of the shrimp becoming hard, as a result of the dehydration caused by the movement of moisture, can be avoided. contained in the shrimp, the temperature of which was increased before the coating, to the coating, as a result the coating loses its feel fragile to the touch. According to the result of the experiments, the coating of those temples heated by a heating method according to the present invention is more humid, compared to those heated only with microwaves at a time immediately after the end of the heating process, but When they are served at the table, the coating regains its fragile feeling to the touch, as the excess water gradually evaporated with time. (modality 7) A seventh modality is described below. Figure 13 shows a heating method, according to the present invention, for heating a food product whose surface is heated before the central part; where (a) shows the temperature within the heating cavity and the temperature of the food product during the heating process; (b) the transition of the moisture within the heating cavity; and (c) the output of the microwaves. Starting from the freezing temperature (-20 ° C), the temperature of the food product passes through the area of maximum ice crystal formation (-1 ° C to -5 ° C), taking some time (point A ). Because the microwaves are absorbed by the food product only slightly up to the point A, from the start, and go deep into the food product, the microwaves are irradiated to the frozen food with full power during the first half of the process. heating, as shown in (c). In order for the microwaves to reach the interior of the food product well, it is important to prevent the surface of the food product from melting or absorbing moisture. Therefore, until the food product begins to partially melt (point A), the temperature control, inside the heating cavity, is suspended, as shown in (b). That is to say, the freezing of the foodstuff is mainly carried out with microwaves, which are capable of passing deep into a foodstuff in the frozen state, while the production of steam is suspended. After passing through point A, the food product, in which the melted part and the frozen part coexist, begin to absorb microwaves significantly. As described above, the molten part (water) shows the dielectric loss several times, up to several tens of times, greater than the frozen part; which makes the temperature difference between the melted and the frozen is greater. Therefore, as shown in (c), the microwave output is gradually decreased to about one fifth or one sixth of the total power, and the heating is maintained allowing heat conduction from the upper part to the lower part . After passing point A, the temperature and humidity inside the heating cavity are adjusted, respectively, to match the state at the end of the heating process of the food product, as shown in (a) and (b) ); consequently, the vapor surrounds the surface of the food product and helps the internal temperature to increase. In a case where the internal temperature is still too low when the surface reached the temperature at the end of the heating (point B), the microwave radiation is terminated at point B, as shown in (c), and is expected to that the internal temperature increases while controlling the temperature and humidity, as indicated in (a) and (b). When applied, e.g., to a burger or curry and rice, the present heating method heats these items completely to the interior, at a good temperature, preventing the surface from becoming too hot and drying or boiling. (mode 8) An eighth embodiment comprising an independent heating fitting will now be described immediately in order to completely avoid condensation of the spray in the heating cavity. As the independent heating accessory, a heating device 30, in addition to a steam generator 15, is provided in the path of the steam discharge, as shown in Figure 14. Before steam generation, a control section initiates the supply of energy to the heating accessory to increase the temperature of the heating cavity. With this constitution, the condensation of the spray on the surface of cold walls, of the heating cavity, is avoided with great certainty. By virtue of the independent heating accessory, the temperature and humidity inside the heating cavity are adjusted so that they do not cause condensation of the spray on the surface of the internal wall of the heating cavity, by means of the control in the supply of energy towards the steam generator 15 and the heating device 30. The effectiveness is remarkable when the environment, inside the heating cavity, is adjusted to have a relative humidity of less than 90%. (mode 9) Now, in the following, a ninth embodiment comprising an independent heating accessory will be described in order to completely avoid condensation of the spray in the heating cavity. Figure 15 shows an example of a microwave heating apparatus, comprising an electric heater in the heating cavity. Among the environment adjustment accessories, the heating device 30 can be replaced with the electric heater 31, for an integrated function. It is not intended to limit the steam generator to a type such as that shown in the present embodiment; it can be a tap heater, or the like, submerged in an ordinary boiler, or attached burning around the tank, for example. In this arrangement in order to allow a free control of the steam temperature, a part of the heater should preferably protrude above the water level of the boiler, so that the temperature of the generated steam can be further increased. (embodiment 10) Now, in the following, another embodiment of the present invention will be described, with reference to the figures. Figure 16 shows a cross-sectional view of a microwave heating apparatus according to another embodiment of the present invention. A magnetron, 14, or an accessory for microwave generation, is provided in a heating cavity, 13, for irradiating microwaves into the heating cavity, 13. On one side of the heating cavity 13 is provided a steam generator, 32, comprised of a non-magnetic material. One end of the steam generator 32 is coupled to the heating cavity, 13, by means of a discharge conduit 33; the other end, with a water reservoir, 12, by means of a flow intake tube, 34. Inside the steam generator 32, a heating element, comprised of a magnetic metal, is housed. Ideally, the steam generator 32 should be filled, for the most part, with the heating element 35. The heating element 35 can be comprised of any material, in any way, as long as it generates heat with magnetic fields; In the present embodiment, a substance that has the form of a foam, or fiber, is used, in order to maximize the contact surface with the water. In the case where the steam generator 32 is comprised of a magnetic material, instead of a non-magnetic material, the heating element becomes unnecessary; in this case, however, the volume of the water remaining in the steam generator 32 increases and consumes more time before it begins to generate steam; therefore, it is necessary to have some ingenuity to insert a hollow body, or something similar, into the steam chamber, in order to reduce the effective volume of water in the chamber, heat the water in advance, or some other mechanism . Around the generator 32, an energizing coil, 36, is provided, which is connected to an inverter of the power supply, 37, to provide an alternating current. With the power supplied from the inverter of the power supply, 37, the excitation coil 36 produces an alternating magnetic field. With the alternating magnetic field, eddy currents are created in the heating element 35, which causes the heating element 35 to generate heat. The water in the steam generator, 32, is heated by the heat generated from the heating element 35, and vapor is vaporized, which proceeds into the heating cavity 13, through the discharge conduit 33. The number 38 denotes a high voltage of the power supply, to supply high voltage to the magnetron 14. A controller, 21, conducts ON / OFF operation, of the power supply inverter, 37, and of the high power supply. voltage, 38, or the energy control of the respective energy sources. Inside the heating cavity 13, a tray 20 is placed, having openings that allow steam to pass through it, to place a food product, 19, on it. The excitation coil 36, by itself, does not generate any heat; instead, the parasitic current causes the heating element 35 to generate the heat, which is conducted directly to the water. Therefore, steam is produced efficiently. The steam generator 32 is defined by a cover, generally cylindrical, made of an insulating material, of a type having a heat resistance and an insulating property such as, for example, heat-resistant glass or porcelain, with a wall thickness greater than the insulation distance with respect to the voltage applied to the excitation coil 36, ie, greater than a sufficient value to avoid any dielectric breakdown that could be effected at the voltage applied to the excitation coil 36. The heating element 35 can be of a metallic, porous material, having a sufficient water resistance and a corrosion resistance as, for example, Ni, Ni-Cr alloy or stainless steel alloy. Figure 17 illustrates the amount of steam in the heating cavity. What Figure 17 shows is the change in the amount of steam within the heating cavity as the heating time elapses; When the heating starts, the steam generator also begins to work, and stops working when the heating is finished. According to the experiment, where the heating element 35 is heated with an output of 400, of the power supply inverter, 37, steam generation started in about 10 seconds, and finished in approximately several seconds after it stopped The warm-up. Accordingly, the start and stop of the steam generation was carried out with a much faster response to the operation of the steam generator, compared to conventional constitutions. In addition, the steam was produced by a substantially small energy consumption. This is because the alternating magnetic field of the excitation coil 36, supplied by the energy supply 37, instantaneously heated the heating element, 35, to heat the water in the steam generator 32, and the steam It was produced efficiently. The efficiency is remarkable when the heating element 35 is comprised of a metal in the form of a foam or continuous fiber, which has a large area of contact with the water. Also due to the fact that the proportion of the volume of water, inside the steam generator 32, is decreased by the existence of the heating element 35, the steam is easily generated by heating only a small amount of water, which allows the quick start of steam generation. In general, the shortest start time is preferred; practically, it should be less than 1 minute, preferably, approximately 10 seconds. (embodiment 11) Figure 18 shows the relationship between the temperature of the food product and the amount of steam, inside the heating cavity of a microwave heating appliance, according to an eleventh embodiment. In Figure 18, the operation of the accessory to generate the microwaves and the steam generation accessory are initiated at the same time, when the heating process is initiated. Also, when the heating ends, the operation of the two previous accessories is interrupted at the same time. Due to the quick start of the steam generator, although the operation of the steam generator is started at the same time as the start of the operation of the microwaves, the food product is cooked both with microwaves and with steam, through most of the 1 cooking / cooking time, with the exception of several initial seconds, when the heating is conducted only with microwaves; consequently, the heating is conducted while the evaporation of moisture from the food product is suppressed. Therefore, a very fine cooking / cooking is implemented, to produce an excellent finish, without loss of adequate moisture of the food product. (embodiment 12) Figure 19 shows the relationship between the temperature of the food product and the amount of steam inside the heating cavity of a microwave heating appliance, according to a twelfth embodiment. In Figure 19, a food product is heated only with microwaves while the food product is in the frozen state, or below 0 ° C, since it is easier for the microwaves to penetrate the frozen food product. The freezer is cooled or continues, and as soon as the temperature of the food product reaches a value almost above zero, a steam generator is started to cook the food product with microwaves and steam. Moisture easily evaporates from the food product, when the temperature of the food product exceeds 0 ° C. The present heating method, however, the food product is surrounded by steam; therefore, it is heated while a preventive measure is taken against the evaporation of moisture. Therefore, the food product can be cooked in a good environment, which results in an excellent finish, conserving adequate moisture, without dehydration. In addition, while the steam generator is put into operation, only for the necessary time, the excessive use of energy is avoided, thus making a contribution to energy saving. (embodiment 13) Figure 20 shows the relationship between the temperature of the food product and the amount of steam inside the heating cavity, of a microwave heating appliance, according to a thirteenth embodiment. In Figure 20, the operation of the microwave generation accessory and the steam generation accessory are initiated at the same time, when the heating process is initiated. In the end, the operation of the steam generation accessory is completed earlier in a certain period of time during which the steam, in the heating cavity, decreases, after which the operation of the microwaves is completed. By doing this, the amount of steam, in the heating cavity, decreases when the heating process is completed, as a result it is easy and safe for when a cook extracts the food product, without being exposed to steam. (embodiment 14) Figure 21 shows the relationship between the temperature of the food product and the amount of steam within the heating cavity of a microwave heating appliance, according to a fourteenth embodiment. In Figure 21, the food product is heated with microwaves with a high power output and the steam generator with low power operation, while the food product is in the frozen state, or at a temperature below zero. Then, as the temperature of the foodstuff reaches a temperature almost above zero, the microwave output is lowered to the midpoint, while the output of the steam generator increases to the temperature of the food product. middle point. After the temperature of the food product reached an average zone, the output of the microwaves is decreased to a low level, while the output of the steam generator is increased to a high level. The outputs of the microwaves and steam are varied, 'accordingly, together with the progress of the heating process. For example, while the food product is still in the frozen state, the freezing is done quickly with microwaves, which have the advantage of penetrating into the ice; and then the food product is gradually heated with an average output of the microwaves and steam in order to prevent the food product from heating in an uneven manner. The average steam output is effective to keep the temperature inside the food product homogeneous, and to avoid evaporation of moisture. In the final stage, where the temperature of the food product increases considerably and it is easy for a non-uniform temperature to be present within the food product, the heating is carried out slowly with a lower output of the microwaves, making use of the heat transfer, or a transferred heating, inside a food product. When the temperature of the food product is high, moisture evaporates easily from the food product. However, in the present embodiment, as the cavity is filled with a substantial amount of steam, evaporation is safely avoided, at the same time the steam works to heat the food product. As a consequence, the dissipation of heat from the surface of the food product is avoided, in addition the food product is heated from the surfaces that surround it, therefore, the food product is homogenously stored, preserving humidity, without dehydration, achieving finely prepared foods. (mode 15) Figure 22 shows a cross-sectional view of a microwave heating apparatus, according to a fifth category. A magnetron 14, or accessory for generating microwaves, is provided in a heating cavity 13, for irradiating microwaves into the heating cavity 13. On one side of the heating cavity 13 is a steam generator, 32, comprised of a non-magnetic material. The bottom of the steam generator 32 is coupled to the heating cavity 31 by means of a discharge duct 33, the upper end with a water reservoir, 12, by means of a flow intake tube 34. A valve 39 is positioned between the flow intake tube 34 and the water reservoir 12, to regulate the flow of water. Inside the steam generator 32, a heating element 35, comprised of a magnetic metal, is received. The heating element 35 is comprised of a metallic substance molded in the form of a continuous foam or fiber, in order to maximize the contact surface with the water. Around the steam generator 32, an energizing coil 36, which is connected to an inverter of the power supply 37, is provided to provide an alternating current. With the energy of the inverter of the power supply 37, the excitation coil 36 produces an alternating magnetic field. With the alternating magnetic field, eddy currents are produced in the heating element 35, which causes the heating element to generate heat. From the upper part of the heating element 35, water is provided, from the water tank 12, by the flow intake pipe 34. The water flow is controlled by the valve 39, so that the water drips only in a quantity necessary for evaporation. The water dripping in the steam generator 32 is heated by the heat generated from the heating element 35 and evaporates, steam coming to the heating cavity 13, through the discharge conduit 33. A fan 40 blows the steam produced in the steam generator 32 to the heating cavity 13. The number 38 denotes a contribution of high voltage energy to supply high voltage energy to the magnetron 14. A controller 21 conducts the ON / OFF operation of the inverter of the power supply 37 and the high voltage power supply 38, or the energy control of the respective energy sources. Inside the heating cavity 13, a tray 20 is placed, which has openings that allow steam to pass through it, to place a food product 19 thereon. The excitation coil 36, by itself, does not generate any heat; instead, the parasitic current causes the heating element 35 to generate heat, to be conducted directly to the water. Therefore, steam is produced efficiently.

According to a heating method with the constitution described above, the water is heated only in a certain amount for evaporation, which results in a limited consumption of water and the almost instantaneous generation of the steam with a small energy consumption. Therefore, the heating start and stop can be carried out instantaneously, which makes it possible to carry out an optimal heating control that is suitable for each of the stages of cooking / cooking. In this way, the food products can be heated / cooked in the most appropriate way for the respective category.

INDUSTRIAL APPLICABILITY According to the present invention, the environment within the heating cavity, such as temperature, humidity, etc., can be controlled to conform to a food product; therefore different varieties of food products can be cooked / cooked in an excellent way. That is to say a microwave heating apparatus, in accordance with the present invention, makes it possible to heat / cook maintaining the internal temperature and the surface temperature of a food product almost identical.

In addition to the heating / cooking of the frozen bread and tempura, already described, the present apparatus is ideal for articles where a plurality of food products are in a package and that of freezing or reheating of which is difficult only with microwaves, eg, a lunch box, as well as for freezing 1 ami ent with the refrigerator, where a frozen item passes through the zone of maximum ice crystal formation and stops at the refrigerator temperature . In addition to food products, a wide variety of materials that exhibit various dielectric losses can be the object of heating. Various industrial fields, where delicate heating processing is required, for example, the dissolution of synthetic resins, softening of binders, drying of woods, etc., will fall within the scope of application. In addition to microwaves, a high-frequency alternating field, such as the heat source, can be used.

It is noted that, in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it refers. Having described the invention as above, the content of the following is claimed as property.

Claims (18)

1. A microwave heating appliance, characterized in that it comprises: - a heating cavity for receiving a heating object; a microwave generation accessory, for irradiating microwaves to the object of heating; a steam generation accessory, to provide steam to the heating cavity; and - control means, for controlling the microwave generation accessory and the steam generation accessory, so that the internal temperature and the surface temperature of the heating object become approximately equal.

2. A microwave heating apparatus, characterized in that it comprises: a heating cavity for receiving a heating object; a microwave generation accessory, for irradiating microwaves to the object of heating; a steam generation accessory, to provide steam to the heating cavity; - detection means for detecting environmental conditions within the heating cavity; and - control means for controlling the microwave generation accessory and the steam generation accessory, according to the output of the detection means, so that the internal temperature and the surface temperature of the heating object become approximately equal .

3. The microwave heating apparatus, according to claim 2, characterized in that the detection means detects temperature.

4. The microwave heating apparatus, according to claim 2, characterized in that the detection means detects temperature and humidity.

5. The microwave heating apparatus according to any of claims 1 to 4, characterized in that, when the heating object is heated in the frozen state, the accessory of the control accessory the output of the steam generation accessory, then that the heating object is defrosted, so that it is greater than the output of the steam generating accessory, while the object is still in the frozen state.

6. The microwave heating apparatus according to any of claims 1 to 4, characterized in that, when the heating object is heated in the frozen state, the control accessory controls the output of the microwave generation accessory, after which the heating object is thawed, to be less than the output of the microwave generation accessory while the heating object was still in the frozen state, and the output of the steam generation accessory, after the heating object has been thawed, to be greater than the output of the steam generation fitting while the heating object is still in the frozen state.

7. The microwave heating appliance according to any of claims 1 to 4, characterized in that, when the heating object is heated in the frozen state, the control accessory controls the output of the microwave generation accessory, in the immediate moment after starting the heating, to be less than the output of the steam generation accessory, later.

8. The microwave heating apparatus according to any of claims 1 to 4, characterized in that, when the heating object is heated in the frozen state, the control accessory controls the output of the microwave generation accessory so that it is reduced gradually, and the output of the steam generation accessory, after the heating object is thawed, to be greater than the output of the steam generating accessory while the heating object is still in the frozen state.

9. The microwave heating apparatus according to any of claims 1 to 4, characterized in that the control accessory reduces the output of the steam generating accessory immediately after the end of heating, of the heating object.

10. The microwave heating apparatus according to any of claims 1 to 4, characterized in that the control accessory controls the humidity inside the heating cavity, so that it is less than 90%.

11. A microwave heating apparatus, characterized in that it comprises: a heating cavity for receiving a heating object; a microwave generation accessory, for irradiating microwaves towards the heating object; a steam generation accessory, to supply steam to the heating cavity; - an accessory for blowing air, to supply an air flow to the heating object; and a control accessory, for controlling the microwave generation accessory, the steam generation accessory, and the air blowing accessory, so that the internal temperature and the surface temperature of the heating object are approximately equal.

12. The microwave heating apparatus, according to claim 11, characterized in that the air blowing accessory carries the air from the outside towards the heating cavity.

13. The microwave heating apparatus according to claim 11, characterized in that the air blowing accessory circulates the air within the heating cavity.

14. The microwave heating apparatus, in accordance with claim 11, characterized in that the control accessory causes the air blowing accessory to remain in operation for a specific time after the output of the microwave generation accessory is terminated.

15. The microwave heating apparatus, according to claim 11, characterized in that the control accessory causes the air blowing accessory to keep running intermittently, during a specific time after the output of the microwave generation accessory It is finished.

16. A microwave heating apparatus, characterized in that it comprises: a heating cavity for receiving a heating object; a microwave generation accessory, for irradiating microwaves towards the heating object; a steam generation accessory, to supply steam to the heating cavity; a heating accessory to prevent dew condensation in the heating cavity; a control accessory, for controlling the microwave generation accessory, the steam generation accessory so that the internal temperature and the surface temperature of the heating object are approximately equal.

17. The microwave heating appliance according to claim 16, characterized in that the heating accessory is positioned between the steam generator and the interior of the heating cavity.

18. The microwave heating apparatus, according to claim 16, characterized in that the heating accessory is placed inside the heating cavity.