EP3502573B1

EP3502573B1 - A rear surface structure for an oven

Info

Publication number: EP3502573B1
Application number: EP18210689.8A
Authority: EP
Inventors: Ehsan Amirabedin
Original assignee: Renta Elektrikli Ev Aletleri Sanayi Ve Dis Ticaret Ltd Sirketi
Current assignee: Renta Elektrikli Ev Aletleri Sanayi Ve Dis Ticaret Ltd Sirketi
Priority date: 2017-12-25
Filing date: 2018-12-06
Publication date: 2021-05-12
Anticipated expiration: 2038-12-06
Also published as: TR201721633A2; EP3502573A1; PT3502573T; ES2882373T3

Description

Technical Field of the Invention

The invention relates to a cooking chamber structure with a novel air-circulation system developed for increasing the energy efficiency of electric ovens and designed for rear surface of cooking chamber of oven.

State of the Art:

Many electric oven types having various designs are known in the state of the art. Oven structures in question differentiate from each other in terms of their cooking chamber structures in their inner parts and of components they include.
When the structures of present art electric ovens are examined, it can be seen that there are differences in designs of fan, fan cover and heating elements in cooking chambers constituting inner portions in general and about circulations of heated air inside the cooking chamber. The elements in question can be positioned such that they can be in different sizes and numbers depending on the designs provided for increasing homogenous heat inside the cooking chamber.
When the designs of state of the art electric oven structures are examined, it can be seen that the most commonly used designs are oven structures having a fan structure with a motor positioned at rear surface of cooking chamber and a heating structure such as resistor etc. positioned close to fan structure. The fan structure positioned at rear surface of the cooking chamber in said design sucks air inside the cooking chamber and passes it through the heating structure nearby and thus makes the sucked air to be heated up. The heated air is transferred back to the cooking chamber from a different point or points depending the related designs thus the temperature of the cooking chamber is increased. The fan structure of said widely used design is positioned right at center point of the rear surface of cooking chamber.
The most essential aspects taken into consideration while constructing the designs of present art oven structures are energy efficiency and homogenous heating systems. The main factor prioritized in works and designs conducted with regard to oven structures is to provide oven structures with high energy efficiency and homogenous cooking chambers.
In order to measure the energy efficiency of the oven structures, measurement techniques that are standardized are used.
The measurement technique applied for measuring the present art oven energy efficiency is basically estimated according to time period spent during bringing temperature value of center of cooking chamber to a certain level and according to energy amount values spent at that stage. Taking said values into consideration, the shorter the measured time the higher energy efficiency. Analogously, the lower level the energy amount spent in the meantime the higher the energy efficiency.
For obtaining high energy efficiency in oven structures, center of the cooking chamber should be rapidly and effectively heated. At this point, the importance of the volume of cooking chamber come to the forefront during distribution of heated air.
One of the essential factors taken into account during the calculation of said energy efficiency is clearance volume value inside the cooking chamber. The clearance volume is calculated by measuring the inner structure dimensions of the cooking chamber. However, while calculating the energy efficiencies of the present art oven structures, there occurs a measurement problem regarding the dimension of the clearance volume.
Height, width and depth dimensions of the chamber are measured by a special apparatus while calculating the clearance volume of the cooking chamber. Taking the rear surface of the cooking chamber of the oven structures in the state of the art into consideration, the fan cover and the fan motor-blade components taking a specific space inside the chamber are also located in the measurement area when measuring the depth value. Because of the elements such as the fan structure, heating element, fan motor, fan cover located at the rear surface of the cooking chamber, the depth measurement is done such that only the distance until the fan cover is measured. The measurement apparatus used cannot reach the distance between the rear surface of the cooking chamber and the outer surface of the oven structure. Thus, the space behind the rear surface of the cooking chamber cannot be taken into account at the end of depth measuring. This causes the clearance volume considered in the calculation of energy efficiency to be smaller than the real volume. Thus, while calculating the energy efficiencies of said oven structures, the measurement is done for heating a space value smaller than the existing one and it is determined that the oven structure has an energy efficiency lower than the real energy efficiency of the oven structure. Said calculation causes the oven structures to appear as if they have a worse energy efficiency than they have in fact. The main reason of said wrong efficiency calculation is the design of the rear surface of the cooking chamber.
Another common problem of electric ovens used in the present art is heat loss problem occurred as result of passing the heated air sucked by the fan structure through the edge parts of the cooking chamber for distributing it into the cooking chamber in a homogenous manner. In plurality of oven structure in the state of the art, connection between the volume behind the rear surface of fan structure and the cooking chamber is obtained by one or more space structures positioned on edges of the rear surface of the cooking chamber. Depending on the fact that heated air is passed homogenously into the cooking chamber through the edge parts of the rear surface of the cooking chamber, the desired homogenous heat distribution cannot be ensured inside the cooking chamber. The heated air sent into the cooking chamber in said structures first has to contact to side surfaces of the cooking chamber. This causes that an amount of heat of the heated air contacting to the side surfaces is transferred to the side surfaces by the heat transmission. Hence, the heated air starts to lose heat before reaching to the center of cooking chamber.
Thus, there occurs a temperature difference between the air masses near the side surface and the air masses in the center and a homogenous heat distribution cannot be ensured inside the cooking chamber. Due to movement direction of the hot air, duration required for the center of cooking chamber to reach desired temperature value is increased. Particularly when measuring the energy efficiency, since the temperature change of the air mass in the center of cooking chamber, the energy efficiency is low in those types of oven structures.
In some cooking chamber structures, there are shelf holes on the side walls. Taking the existence of said shelf holes and the cases that the heated air firstly transferred by contacting to the side walls of the cooking chamber into account, more heat losses occur in said structures. In oven structures of that type, an amount of the heated air sent to the side walls of cooking chamber exits from the cooking chamber passing through the shelf holes on the side walls. As a result of exit of an amount of heated air mass from the cooking chamber through the shelf holes, energy loss occurs depending on heated mass loss. This increases the time period needed for bringing the temperature level inside the cooking chamber up to a desired level. Therefore, energy efficiency of these oven structures is low.
One of the factors causing the low energy efficiency is locations of the fan structures in the oven structures in which the fan structures are positioned right at the middle point of the rear surface of cooking chamber in the present art. An undesired situation is encountered because of measuring the heat change of air mass right in the center of cooking chamber when measuring the energy efficiency and due to the fact that fan structure facing to that air mass sucks that air mass for heating it. Depending on the air flow created by sucking process performed by the fan, the air mass in the center of cooking chamber moves. This movement firstly causes temperature in the center of cooking chamber to partly decrease at the instant when the oven is turned on. Thus, it takes more time for the temperature in its center to rise up to a desired level. This creates a substantial disadvantage in term of energy efficiency. Because of all these reasons, measured energy efficiency value is at low level in the oven structures in which the fan structure is located right on the middle point of the rear surface of cooking chamber.
In order to keep measured energy efficiency level high and to ensure both effective and rapid cooking, another method applied in the present art is to use oven systems having double fan structures. In this case, more raw materials are required for manufacturing these oven structures. Particularly, due to using more than one fan, plurality of elements such as fan motor, fan cover and resistor are used. This creates a substantial disadvantage in term of costs.
In the oven structures used in the state of the art, the heating element through which the air sucked by the fan is passed for being heated has an active role in terms of energy efficiency. Said heating elements are resistor structures generally having heating rings in circle shapes. In said resistor structures, inner portions of the heating rings have large circumferential gaps. The air mass to be heated is passed through these gaps. Since the gap through which the air mass is passed is large, surface area of the air mass contacting to the heater is at low level. The air mass passing right through the middle section cannot contact to the heating surfaces. Therefore, the air passed through large gaps cannot be heated efficiently and the energy efficiency value of the oven structure is low.
In the patent application numbered US2010229847A1 of the state of the art, a novel rear surface of cooking chamber developed for ovens is disclosed. Design of said rear surface is different from the commonly used present art oven structures. Fan structure performing suction process of air to be heated is not located on the center of said rear surface. Passage of heated air into the cooking chamber is performed via hole structures located at any point on the rear surface. Although said invention has different design, it cannot overcome the problems of energy efficiency encountered by the present art oven structures. Particularly taking the holes by which, the heated air is passed into account, it can be seen that there is no possibility for the heated air to be homogenously distributed inside the cooking chamber. Said invention is insufficient to ensure more rapidly heating of the center of cooking chamber. Therefore, it leads to an oven structure having a low energy efficiency.
One of the prior art, JP S56 21116 U , discloses a microwave oven which has improved hot air generator. This oven comprises high frequency heating chamber, magnetron which supplies highfrequency electric wave, hot air generator, an enclosure wherein a duct-shaped ejection is formed inside, a hot air circulation path, heater located in the hot air circulation path, fan (17), hot air outlet, operating means.
In the patent application numbered US2009090347A1 of the state of the art, a novel oven structure having a rear surface design of which is changed is disclosed. Fan structure performing suction process of air to be heated is located on the center of rear surface. Depending on said rear surface design, the fan structure sucks the air mass right in the center of cooking chamber, thus creating an air flow in the center of cooking chamber. This leads prolonged time period needed for bringing the center temperature of the cooking chamber up to a desired level. Since temperature change duration of the cooking center is checked when measuring the energy efficiency, the energy efficiency of said oven structure seems low.

Aim of the Invention:

Aim of the invention is to provide a novel oven structure having a cooking chamber that ensures a high energy efficiency.
Another object of the invention is to minimize amount of energy loss encountered in ovens.
A further object of the invention is to provide a novel cooking chamber having heating element with high efficiency for ovens.
A further aim of the invention is to provide a novel oven structure that allows inner dimensions of cooking chamber volume of which is to be calculated for measuring its energy efficiency to be more accurately measured.
Another object of the invention is to provide a novel oven structure in which the temperature of air in the center of cooking chamber is ensured to be brought up to desired level in a faster manner by means of rear surface of cooking chamber it has.
Another object of the invention is to provide a novel oven structure which allows the heated air to be homogenously distributed inside the cooking chamber by means of the rear surface structure of cooking chamber it has.

Description of the Figures:

Fig. 1.: Perspective view - mounted view of rear surface of cooking chamber on oven structure
Fig. 2.: Rear perspective view - rear surface of cooking chamber
Fig. 3.: Front perspective view - rear surface of cooking chamber
Fig. 4.: Rear perspective view - rear surface of cooking chamber inner portion of which is seen
Fig. 5.: Front perspective view - rear surface of cooking chamber inner portion of which is seen
Fig. 6.: Front view - mounted view of rear surface of cooking chamber on oven structure

The parts shown in the figures are enumerated individually and names of the parts corresponding to these numbers are as follows:

1. Rear Surface
2. Air Duct
3. Fan
4. Helical Duct
5. Distribution Hole
6. Resistor
7. Motor

Description of the Invention:

The invention relates to a cooking chamber structure with a novel air-circulation system ensuring the increase of energy efficiency of electric ovens and designed for rear portions of cooking chamber of oven.
The subject matter structure is rear surface (1) structure designed considering the energy efficiency and used inside cooking chamber portions. As shown in Fig. 1 and Fig. 6, said rear surface (1) structure is positioned at rear portions of cooking chambers.
The subject matter rear surface (1) is a structure used by being positioned at front section of outer rear surface of oven structure on the rear side and on the inner side of cooking chamber. When the rear surface (1) is placed at the inner section of the cooking chamber, it is positioned such that it contacts to lower and upper surfaces as well as side surfaces of the cooking chamber. Above-mentioned positioning process can be optionally performed as desired over the edges of the rear surface (1). Assembly by screws is the primary assembly method that can be preferred. This assembly process is performed such that the rear surface (1) is mounted inside the cooking chamber via screws located to screw sockets on the edge sections of the rear surface (1).
As shown in Fig. 5 and 6, there is an air duct (2) in form of round gap right at the middle portion of the rear surface (1). Said air duct (2) faces right middle section of the cooking chamber and has an active role in passing the heated air to the center of the cooking chamber efficiently. The air duct (2) is located right at the center of rear surface (1).
An axial fan (3) structure is located on any point around the air duct (2) such that it is close to the air duct (2). Said fan (3) structure is the structure sucking the air to be heated inside the cooking chamber. There is a fan (3) motor (7) making the fan (3) work right behind the fan (3) structure. Said motor (7) and the fan (3) structures may be any model suitable for use inside an oven depending on the preference of the user.
On the surface at the rear side of the air duct (2), there is a circumferential helical duct (4) structure positioned such that it completely surrounds the edge surface of the air duct (2) . Said helical duct (4) has a structure inner of which is in the form of helix gap. The helix gap structure inside the helical duct (4) has a diameter large enough to allow at least an air passage therethrough. An end of the helical duct (4) is connected to the fan (3) structure and encloses the fan (3) structure. Thereby, the air, to be heated, sucked by the fan (3) from inside the cooking chamber enters into the helical duct (4). The air entering into the helical duct (4) can go along the helix gap in is inner structure.
The air, to be heated, sucked by the fan passes through the resistor (6) structure positioned near the fan (3) structure such that it is inside the helical duct (4), immediately before entering into the inner structure, in the form of helix gap, of the helical duct (4). Said resistor (6) structure is a resistor (6) structure in zigzag form and in other similar resistor forms. Hence, the air sucked by the fan for heating contacts the hot body portion of the resistor while passing through the resistor (6) structure which is in zigzag and similar form and proceeds towards the inside of helical duct (4). Since the space of the resistor (6) structure is small, much of the air mass sent into the helical structure (4) contact to the resistor (6) body. As a result of said contact, the air mass temperature of which is lower takes heat from the resistor (6) structure and its temperature is increased by means of said heat transfer.
The air sucked by the fan (3) exits from the distribution hole (5) located on the inner part of the helical duct (4) by passing through the structure of the helical duct (4) that is in helix gap form. The distribution hole (5) is located on the inner surface at the inner side of the helical duct (4). By virtue of the helix inner structure of the helical duct (4), the air performing a cyclonic motion while passing through the helical duct (4) continues to perform cyclonic motion after being discharged from the distribution hole (5). The heated air discharged from the distribution hole (5) performs a cyclonic flow while moving towards the center on cooking chamber to which the air duct (2) faces. The air discharged from the distribution hole (5) is sent to the center of cooking chamber by performing a low speed cyclonic flow. Since the air duct (2) faces exactly towards the center of cooking chamber, heated air discharged from the distribution hole (5) performs a cyclonic flow right towards the center of cooking chamber. By this means, heated air mass directly reaches to the center of cooking chamber and the temperature of the center of cooking chamber can be increased in a short time.
The heated air sent to the center of cooking chamber by performing low speed cyclonic motion is homogenously distributed into the cooking chamber by the effect of cyclonic motion. Since the center of cyclonic motion performed by the heated air and the center of cooking chamber intersect, the hot air radiated outwardly is radiated at equal speed and homogenously from the center of cooking chamber towards the sides. This ensures a homogenous heating of the cooking chamber. The air radiated to the sides of cooking chamber and the temperature of which is decreased is heated again by the fan (3) which is positioned to any point on the side surface of the air duct (2) and is discharged again through the distribution hole (5) and performs a cyclonic motion towards the center of cooking chamber.
The subject matter rear surface (1) structure provided in order to ensure high energy efficiency in the oven structures ensures that the heated air having low speed and proceeding by performing cyclonic motion is sent to the center portion of the cooking chamber. When said heated air is sent into the cooking chamber, it is directly sent to the center of cooking chamber. Thereby, the heat loss level that may occur until the heated air reaches to the center of cooking chamber is minimized. Hence, the center of the oven structure in which said rear surface (1) is employed can have high temperature in a short time by low energy amount. This ensures both that said oven structure has high energy efficiency and that it gets high scores at the result of energy efficiency measurements to be conducted for the oven structure.
While the rear surface (1) structure has air duct (2) space at its middle section, depth value can be maximally measured when calculating the clearance volume of the cooking chamber. As the apparatus measuring the depth value can reach to rear outer surface at the rear side of the oven structure be being passed through the air duct (2), the depth value that can be measured is the maximum value. This ensures that the maximum value of the cooking chamber volume is taken into account during calculating the energy efficiency of the oven structure and aids for more accurate calculation of the energy efficiency. Since the calculated clearance volume is not lower than the real clearance volume, both more accurate and results with better scores can be achieved when the energy efficiency is measured.
The oven structures having much better energy efficiencies can be provided by means of the subject matter rear surface (1) structure. By means of the air duct (2) structure in the form of space of said rear surface (2), an air flow can be created, wherein the heated air can effectively heat the cooking chamber. By means of the helical duct (4) positioned on the edges of the air duct (2) and its inner structure, it is enabled that the heated air can perform cyclonic motion and can move towards the center of cooking chamber by a cyclonic flow.
Depending on the subject matter rear surface (1) structure, by means of the cyclonic flow that can be performed by heated air, it is ensured that the cooking chamber can be homogenously heated. By means of the fact that the fan (3) structure sucking the air mass to be heated inside the cooking chamber is positioned close to the sides instead of the center of rear surface (1), the suction process performed by the fan (3) does not negatively influence the temperature of the center of cooking chamber. The suction flow created by the fan (3) occurs at a different point from the center of cooking chamber and the air flow created by the fan (3) does not decrease the temperature of the center of cooking chamber. This aids in making the cooking chamber reach the desired temperature in shorter time, thus ensuring the increase of energy efficiency.
By means of the fact that the resistor (6) structure through which the air, to be heated, sucked by the fan (3) structure is being passed has small spaced shape, the sucked air is effectively heated. Effectively heated air by means of the structure of the subject matter rear surface (1) proceeds inside the cooking chamber with a minimum heat loss. Hence, a rear surface (1) that enables very high energy efficiency for oven structures is provided by said present invention.

Claims

A rear surface structure (1) configured to be positioned at a rear portion of an oven such that it contacts lower and upper surfaces as well as side surfaces of the cooking chamber, wherein said rear surface structure (1) comprises an air duct (2) in the form of a round gap positioned right at the middle portion of the rear surface structure (1),
a fan (3) located on a point around the air duct (2) such that it is close to the air duct (2) and configured to suck the air to be heated from inside the cooking chamber,
a circumferential helical duct (4) provided on the surface at a rear side of the air duct (2), positioned such that it completely surrounds edge surface of the air duct (2)and having a helix gap shaped inner structure having a diameter big enough for passage of air, an end of the circumferential helical duct being connected to the fan (3) and enclosing it such that the air to be heated, sucked by the fan (3) from inside the cooking chamber enters into the circumferential helical duct (4), wherein the helix inner structure of the circumferential helical duct (4) is such that the air performs a cyclonic motion while passing through the circumferential helical duct (4), a resistor (6) located inside the circumferential helical duct (4) close to the fan (3) such that air to be heated, sucked by fan (3) passes through the resistor (6) immediately before entering into the inner structure, in the form of helix gap, of the circumferential helical duct (4) and ensuring that air is heated,
a distribution hole (5) located on an inner surface at an inner side of the circumferential helical duct (4), such that air sucked by the fan (3) exits from the distribution hole (5) by passing through the circumferential helical duct (4) and continues to perform a cyclonic motion towards the center of the cooking chamber after being discharged from the distribution hole (5).
A rear surface structure (1) according to Claim 1, characterized in that said resistor (6) structure is in zigzag form.