GB2176378A

GB2176378A - Air flow control in cooking apparatus

Info

Publication number: GB2176378A
Application number: GB08612515A
Authority: GB
Inventors: Julius Husslein; Helmut Hess; Werner Schnabel; Herbert Steiner
Original assignee: Bosch Siemens Hausgerate GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 1985-05-30
Filing date: 1986-05-22
Publication date: 1986-12-17
Also published as: DE3519423A1; GB2176378B; IT1189145B; FR2582783A1; JPH0743233U; DE3519423C2; FR2582783B1; IT8620471A0; IT8621859V0; GB8612515D0; IT8620471A1; JPS61276629A

Abstract

A cooking appliance possesses high-frequency heating equipment (6), a grill heater element (5) and optionally also further heater elements to provide, for example, upper and/or lower heat. A cooking chamber (2) is ventilated, during high-frequency operation, by an air current introduced into the chamber for removal of vapour and prevention of condensation at a cooking chamber door (3). A setting element, for example an air flap (12), which is settable by a selector member (21), is provided for the control of the air current. The flap (12) is also disposed in an open setting at least for the grilling operation setting, so that ventilation of the chamber (2) takes place then as well. <IMAGE>

Description

SPECIFICATION Air Flow Control in Cooking Apparatus The present invention relates to cooking apparatus and has particular reference to airflow control in such apparatus.

Provided externally of a cooking chamber in a known cooking appliance (DE--OSS-31 44 493) is a high-frequency generator which is connected by way of a waveguide with the chamber. Associated with the generator is a blower for cooling thereof, wherein a part of the air utilised for cooling the generator is introduced into the cooking chamber and, through intensive ventilation of the chamber in the case of high-frequency operation, ensures that moisture emanating from food being cooked does not condense in the interior of the chamber, in particular on a front glass pane of the cooking chamber door. In this case, the cooling air system is closable towards the cooking chamber at the chamber inlet point in dependence on the mode of operation.Ventilation of the chamber is also provided in the case of combined operation with high-frequency energy and heat energy.

It would be desirable, in a cooking appliance with different heating systems, such as microwave operation and grilling operation, in all modes of operation to prevent impairment of the appliance through the vapours generated in the cooking chamber.

According to the present invention there is provided cooking apparatus comprising a cooking chamber, first heating means arranged in the chamber for grill heating therein, second heating means associated with the chamber for highfrequency heating therein, air current generating means for generating an air current, guide means for guiding such air current into the chamber and a flow control element to control flow of the air current into the chamber according to the mode of heating therein, the element being settable in a first open setting associated with operation of the first heating means and in a second open setting, different in flow resistance from the first setting, associated with operation of the second heating means.

Hitherto, it has been presumed that it is disadvantageous in the operation of an oven with conventional heat sources, for example with upper or lower heat or grill heater element, if the heat generated in the interior of the oven is conducted out by forced ventilation. It has now proved that ventilation of the cooking space at least during grilling operation does not have a deleterious effect on the grilling result in respect of quality and time, since the heat transfer from the heat source takes place predominantly through heat radiation.Thus, even with conventional operation of the apparatus, for example grilling operation, ventilation of the cooking chamber can take place so as to prevent the moist vapour, which arises particularly during grilling, from precipitating in the cooking chamber, for example at a chamber door or at seals surrounding the door, such vapour being conducted out by the flowing air. Forthis purpose the flow control element, for example, a ventilation flap, is settable into at least two opening settings.

Preferably a vapour exhaust channel is arranged in the apparatus to connect with an outflow channel from the air current generating means, for example a blower, the channel leading directly into the open and intermixing of the cooling air with moist vapours taking place in the channel. In that case, in particular, it is advantageous even in baking or roasting operation, to slightly open the control element so that an air current of excess pressure arises in the flow channel leading from the blower to the cooking chamber, which prevents the vapour due to an excess pressure formed in the cooking chamberfrom passing into the flow channel and from there into a switch space.Such.an excess pressure in the cooking chamber could be produced by the excess pressure at the pressure side of the blower, which propagates by way of the vapour exit channel as far as into the cooking chamber.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawing, the single figure of which is a schematic elevation of part of cooking apparatus embodying the invention.

Referring now to the drawing, there is shown part of a cooking appliance comprising a housing 1 defining a cooking chamber 2, which is closable by a, for example tiltable, door 3. Disposed above the chamber 2 is a space 4 in which control and regulating equipment of the appliance is housed.

The appliance is equipped with, for example, a high-frequency generator 6 for microwave operation, with ventilation equipment and with heater elements. The high-frequency generator 6 is arranged in the space 4, which is connected with the chamber 2 by way of a waveguide (not shown). The appliance also possesses electrical resistance heater elements, for example a grill heater element 5.

For cooling of the magnetron, or transformer thereof, of the generator 6 is a cooling blower 7, connected to which in terms of air flow is an air guide 8, extending from which is an outflow channel 9 communicating directly with the oven by way of a channel 10, as well as a flow channel 11,which opens directly into the chamber 2 and is directed obliquely against the door 3. Disposed in the region of the junction of the channels 9 and 11 is an air flap 12, which is tiltable about a pivot axis 13. The air flap 12 is connected with one limb 14' of a restoring loop spring 14, the other limb 14" of which is located in a stationary position. The spring urges the flap 12 out of a closed setting, drawn in dashed lines, into an open setting, drawn in solid lines, in which the flap can abut against an abutment (not shown).In the open setting shown in the figure, the two channels 9 and 11 are opened in such a manner that the air current emanating from the cooling blower 7 is subdivided and only a proportion flows into the channel 11 and the chamber 2. The flap 12 has a projection 15 concentric with the axis 13 and coupled by way of a spring 16 with a rocker 18, which is pivotably mounted at 17. The other end of the spring 16 is fastened to one end of the rocker, the other end of which has a fork-like bearing point 19 for a pull rod 20. The rocker 18 and rod 20 form a lever gear. This lever gear stands directly in mechanical connection with a control disc 21, which is firmly connected with a selector switch, constructed as a rntaryknob (not shown), of the appliance.By means of this switch, the different modes of operation, for example "microwave operation", "grilling operation" and "baking, and roasting operation", can be set.

Disposed at the rearward side of the ceiling of the chamber 2 is an air exit opening 22 with adjoining oufflow channel 23 which, as illustrated in dashed lines, opens into the channels 9 and 10 for the oufflowing cooling air.

For pure microwave operation, during which exclusively the high-frequency generator is switched on, the flap 12 completelyfrees the flow cross-section of the channel 11 so that a relatively strong air current prevails in the chamber 2. In that case, the vapour emanating from food being cooked is drawn off by the air current and prevented from precipitating on the chamber walls, particularly at the inside of the door 3, the vapour being conducted out through the air exit opening 22, the oufflow channel 23 and the channels 9 and 10. The flap 12 is disposed in an open setting even in the case of combined operation with high-frequency heating and conventional resistance heating.In the case of pure grilling operation, thus when only the grill heater element 5 is switched on, through appropriate rotation of the selector switch, i.e.

through the selection of the mode of operation "grilling", the flap 12 is set byway of the lever gear into an open setting in which the flap closes the flow cross-section by about 30% with respect to the full open setting at high-frequency operation. In this case, the vapour arising during grilling is similarly conducted out by the air current. An intermixing of the hot vapourwith the cool air emanating from the blower takes place in the channel 9, while the air mixture at the exit side has a relatively low temperature. In the operational setting "baking roasting", as well,the flap 12 is disposed in an open setting, preferably in one in which it closes the flow cross-section by more than 90%.In this manner, a weak air current is produced in the channel 11 during this mode of operation and a certain excess pressure is generated by which vapour arising during baking and roasting is prevented from entering into the channel 11 and getting into the space 4. Such an excess pressure is necessary when the exit opening 22 for the vapour is directly connected with the channels 9 and 10, as shown in the figure. Ifthis excess pressure were not present, then the excess pressure built up in the channel 9 by the blower 7 could propagate by way of the outflow channel as far as the chamber 2, whereby the vapour could be impressed into the flow channel 11.

The open settings of the airflap 12, which are associated with different operational settings of the selector switch, can be realised in simple manner by appropriate construction of the control disc 21,for example similar two that described in DE-OS- 33 37 147 with reference to Fig. 2.

Claims

1. Cooking apparatus comprising a cooking chamber, first heating means arranged in the chamber for grill heating therein, second heating means associated with the chamber for highfrequency heating therein, air current generating means for generating an air current, guide means for guiding such aircurrentintothechamberand a flow control element to control flow of the air current into the chamber according to the mode of heating therein, the element being settable in a first open setting associated with operation of the first heating means and in a second open setting, different in flow resistance from the first setting, associated with operation of the second heating means.

2. Cooking apparatus as claimed in claim 1, comprising third heating means arranged in the chamber for baking or roasting heating therein, the element being settable in a third open setting, different in flow resistance from each of the first and second settings, associated with operation of the third heating means.

3. Cooking apparatus as claimed in claim 2, wherein the element in the first setting provides almost complete opening of a flow cross-section of the guide means, in the second setting closes the flow cross-section by substantially 30 percent and in the third setting closes the flow cross-section by at least 90 percent.

4. Cooking apparatus as claimed in claim 3, wherein the element in the third setting closes the flow cross-section by substantially 95 percent.

5. Cooking apparatus as claimed in any one of the preceding claims, wherein the chamber is provided with an air entry opening communicating with the guide means and an air exit opening communicating with an outflow duct extending from the air current generating means to an outlet positioned for discharge of air externally of the apparatus.

6. Cooking apparatus as claimed in any one of the preceding claims, wherein the element comprises a flap arranged at an inlet of the guide means.

7. Cooking apparatus as claimed in any one of the preceding claims, wherein the element is coupled to and actuable by a selector-member for selection of the different settings of the element.

8. Cooking apparatus substantiaily as hereinbefore described with reference to the accompanying drawing.