EP0794390A2

EP0794390A2 - Fan-heater unit

Info

Publication number: EP0794390A2
Application number: EP97102626A
Authority: EP
Inventors: Claudio Del Fabbro
Original assignee: IRCA SpA Industria Resistenze Corazzate e Affini
Current assignee: IRCA SpA Industria Resistenze Corazzate e Affini
Priority date: 1996-03-04
Filing date: 1997-02-19
Publication date: 1997-09-10
Anticipated expiration: 2017-02-19
Also published as: IT241548Y1; EP0794390B1; ITPN960013U1; DE69729135T2; ATE267364T1; DE69729135D1; EP0794390A3

Abstract

The invention refers to a so-called fan-heater unit, adapted to be included in an apparatus such as a fan-assisted or forced-convection food cooking oven for catering or commercial applications. The unit comprises at least a tangential-type fan (32) mounted with its shaft extending vertically and supported at both its ends by rolling-type journal bearings (44, 46). An electric motor (38), a driving belt (35), driving and driven pulleys (39 and 37, resp.) are used to drive the fan.

The main feature of the invention is that the journal bearings (44, 46) are housed in the walls of channels (53, 61), through which a flow of cooling air taken in from the outside ambient is caused to pass. In a preferred manner, the same walls (53, 61) are also the walls of other channels (57, 65) through which cooling air taken in from the outside ambient is caused to flow as well. Even the driving belt (35) and the pulleys (37, 39) are preferably immersed in the flow of cooling air. Advantages: Possibility for moving parts, in particular standard-type rolling journal bearings to be used, without this impairing reliability to any extent.

Description

The present invention refers to a fan-heater unit, adapted to be included in an apparatus such as a fan-assisted or forced-convection food cooking oven for catering or commercial applications, comprising: heating elements, at least a tangential-type fan mounted with vertically orientated axis and supported at both its ends by rolling-type journal bearings, at least an electric motor to indirectly drive said fan.
A number of patent specifications are known to disclose industrial and/or catering-type cooking ovens provided with electric heating elements and tangential fans to generate a forced circulation of hot air in a cooking cavity thereof.
Examples of ovens with a construction of the above cited kind are for instance described in US-A-3 905 760 and DE-GM-74 24 900.
To the best knowledge of the Applicant, however, no practical implementation of any such invention on an industrial scale is known up to now. The Applicant therefore believes that this may most probably be ascribed to the inability that has generally been shown up to now to solve the problems in connection with the mechanical reliability of moving parts, due to the high temperature which those parts are exposed to in the particular field of application considered.
It in fact seems that no standard, ie. off-the-shelf rolling-type bearing elements, such as those which are currently found in manufacturers' catalogues, are actually available which are capable of operating for prolonged periods of time under combined high-temperature and high-speed conditions, considering that the temperature in the cooking cavity of such ovens may reach as high as 300°C and that good cooking performance results are only ensured in the presence of an appropriate velocity of the flow of the circulated hot air, which implies a revolution speed that must certainly be in excess of 1000 rpm.
It therefore is a purpose of the present invention to provide a construction enabling standard-type rolling journal bearing to be used thanks to a special cooling system adapted to ensure optimum mechanical reliability of the moving parts.
According to the present invention, this and other aims are reached in the arrangement of the heating elements and at least a motor-driven fan in a so-called "fan-heater unit" according to the characteristics recited in the appended claim 1.
Further characteristics are the subject of the subsequent claims.
A preferred, although non-exclusive embodiment of the fan-heater unit according to the present invention will be illustrated in the description given below by way of non-limiting example. For reasons of greater clarity, in the given example such a fan-heater unit is illustrated as associated to a catering-type or professional-kitchen cooking oven, with reference to the accompanying drawings in which:

Figure 1 is a schematical, prespective view of the oven, as seen from behind, in which the flow-path of the cooling air is illustrated;
Figure 2 is a view of the oven as sectioned horizontally along the II-II plane of Figure 1;
Figure 3 is a view of the oven as sectioned along the III-III line of Figure 2;
Figures 4 and 5 are views of the oven as sectioned horizontally along the IV-IV line and vertically along the V-V line of Figure 3, respectively.

As illustrated schematically in Figure 1, a fan-assisted, forced-convection cooking oven for catering applications comprises an outer casing, which is generally referred to at 1 and encloses a substantially parallelepiped cooking cavity 2. The food items to be cooked are filled, in a traditional manner which is largely known to those skilled in the art, into said cooking cavity 2, which is surrounded by thermally insulating material and is provided on the front side with a door 4. On the side of said cooking cavity 2, and duly separated therefrom by the provision of a vertical partition wall 5, the oven further comprises a so-called control cavity 6, which is arranged to accomodate all of the control and auxiliary devices (not shown) of the oven and carries on its front side a control panel 7 with the various actuation members 8 of the control devices 9.
On the bottom plate 10 of the outer casing of the oven, in correspondence of said control cavity 6, there is provided the suction opening 11 of an electric fan 12 (Figs. 3 and 4). According to the invention a continuous flow of air is in fact brought about in view of ensuring the cooling of not only the control, drive and auxiliary devices and members of the oven, but also the moving parts of the fan-heater unit. Through the opening 11, the required cooling air is in fact taken in from the surrounding ambient and, after having covered a definite flowpath inside the fan-heater unit, is exhausted from the rear side 13 of the outer casing of the oven through appropriate upper and lower exhaust apertures 14, 15 and 16, 17, respectively, as this will be more clearly explained further on.
As this has already been mentioned above, the forced circulation of the hot air for food cooking purposes is generated by a so-called fan-heater unit which is built in the oven. Such a unit is appropriately arranged behing a vertical wall 20 which, in a manner that is generally well-known to those skilled in the art, defines the hot- air suction section 21, 22 and the hot-air delivery section 23, 24 (Figure 2) inside the cooking cavity 2.
The fan-heater unit therefore comprises a pair of counterrotating tangential fans 31 and 32, as well as electric heating elements 33 and 34. Said tangential fans 31 and 32 are driven, through a driving belt 35 and pulleys 36, 37, by a single electric motor 38, which is in turn provided with a pulley 39 (Figure 4) and interconnected with the oven control means. The electric motor 38 is appropriately arranged in the rear portion of the control cavity 6, which thing has the advantage of doing away with the need for providing special "ad hoc" space for the same motor and, in particular, the need for increasing the overall depth of the oven. Furthermore, both the motor 38 and the tangential fans 31 and 32 are arranged with their axes extending vertically.
In a per sè already known manner, the shafts 41, 42 of the fans 31, 32 are supported by upper and lower rolling- type journal bearings 43, 44 and 45, 46, respectively.
According to the main feature of the present invention, as better illustrated in Figures 3 and 5, said upper rolling bearings 43, 44 have their housing in an upper plate 51, while said lower rolling bearings 45, 46 are housed in a lower plate 52. Both said upper plate 51, on which also the motor casing 30 is mounted in a cantilever-type manner, and said lower plate 52 have a C-shaped cross-sectional profile.
Said upper plate 51 is separated from the cooking cavity 2 by a proximal upper channel 53 for the cooling air, as well as by a layer of thermally insulating material 55. The proximal channel 53 extends substantially all over the width of the cooking cavity 2, from an opening 54 in the vertical partition wall 5, near the motor 38, to the already cited exhaust aperture 15 on the rear side 13 of the outer casing of the oven. The lower side of the rolling bearings 43, 44 lies therefore inside the proximal channel 53. The upper plate 51 is enclosed between walls 56a, 56b, 56c which, with the same plate 51, form a distal upper channel 57 for the cooling air, which runs parallelly to said proximal channel 53. The distal channel 57 begins at a section 58 inside the control cavity 6 and, running around the driving belt 35 and pulleys 36, 37 and 38, extends along the upper side of the rolling bearings 43 and 44, up to the already cited exhaust aperture 14 on the rear side 13 of the outer casing of the oven.
Thanks to such a construction, the upper rolling bearings 43, 44 associated to the tangential fans 31, 32 are intensively cooled by forcedly circulated air flowing along both sides of the support plate 51 thereof. In this manner, it is possible for the bearings to be selected among the standard, ie. off-the-shelf ones with clear benefits from a technical-economical point of view and without any detrimental effect as far as reliability is concerned. In turn, the driving belt 35 is also immersed in a flow of cooling air and this is again effective in ensuring a high extent of reliability.
The lower plate 52, which supports the lower rolling bearings 45, 46 associated to the tangential fans 31, 32, is separated from the cooking cavity 2 by a lower proximal channel 61 for the cooling air, as well as a layer of thermally insulating material 63. The proximal channel 61 extends substantially all over the width of the cooking cavity 2, starting from an opening 62 in the vertical partition wall 5 up to the already cited exhaust aperture 16 on the rear side 13 of the outer casing of the oven. The upper side of the rolling bearings 45 and 46 therefore lies inside the proximal channel 61. The lower plate 52 is enclosed between walls 64a, 46b, 46c which, with the same plate 52, form a distal upper channel 65 for the cooling air, which runs parallelly to said proximal channel 61. The distal channel 65 extends from a section 66 up to the already cited exhaust aperture 17 on the rear side 13 of the outer casing of the oven.
Thanks to such a construction, also the lower rolling bearings 45 and 46 associated to the tangential fans 31 and 32 are intensively cooled by forcedly circulated air flowing along both sides of the support plate 52 thereof, so that what has been said above in connection with the upper rolling bearings 43, 44 similarly applies also to said lower rolling bearings.
A further advantage offered by the present invention should finally be duly emphasized. As anyone skilled in the art is well aware of, after the oven is turned off at the end of the cooking duties, it may quite frequently occur that, owing to thermal inertia effects, heat is transferred from the cooking cavity 2 to the devices housed in the control cavity 5 and the control panel 7, as well as to moving parts, particularly to the rolling bearings 43, 44, 45, 46 and the driving belt 38. Thanks to the presence of the afore cited channels 53, 57, 61, 65 above and below the cooking cavity 2, even if the electric fan unit 12 has been switched off, a natural air flow takes transitorily place between the opening 11 in the bottom plate 10 and the apertures 14, 15, 16, 17 on the rear side 13 of the outer casing of the oven. This cooling effect is sufficient to prevent the temperature of the above cited devices and moving parts from rising, albeit temporarily, to hazardous levels.
Although the above described one has to be intended to represent a preferred embodiment of the present invention, it will be appreciated that it is within the capabilities of those skilled in the art to use such teachings to derive further variants of the same innovative concept. In particular, fan-heater units using non-electric heating elements (eg. gas-fuelled elements) and/or any number of tangential fans other than two may be developed without departing from the scope of the present invention.

Claims

Fan-heater unit, adapted to be included in an apparatus such as a fan-assisted or forced-convection food cooking oven for catering or commercial applications, comprising: heating elements (33, 34), at least a tangential-type fan (32) mounted with its shaft (42) extending vertically and supported at both its ends by rolling-type journal bearings (44, 46), at least an electric motor (38) to indirectly drive said fan (32), characterized in that said rolling journal bearings (44, 46) are housed in first walls (51, 52) of at least a first upper and lower channel (53, 61), respectively, through which a flow of cooling air taken in from the outside ambient is caused to pass.
Fan-heater unit according to claim 1, characterized in that second walls (56a, 56b, 56c; 64a, 64b, 64c) extend at a distance from said first walls (51, 52) so as to form with said first walls a second upper and lower channel (57, 65), respectively, through which a flow of cooling air taken in from the outside ambient is caused to pass.
Fan-heater unit according to claim 1 or 2, characterized in that said first channels (53, 61) extend substantially all over the width of the cooking cavity (2) of the oven, under interposition of thermally insulating material (55, 63).
Fan-heater unit according to claim 2 or 3, characterized in that inside at least one of said second channels (57) there are housed the pulley (37) of the tangential fan (32), the pulley (39) of the driving motor (38) and the therewith associated driving belt (35).
Fan-heater unit according to any of the preceding claims, characterized in that it comprises at least two tangential fans (31, 32) driven by a single motor (38) in opposite directions of rotation through a single driving belt (35), said motor (38) being housed inside a control cavity (6) situated on the side of the cooking cavity (2) of the apparatus housing the fan-heater unit, but separated therefrom by a layer of thermally insulating material (3) and a partition wall (5).
Fan-heater unit according to any of the preceding claims, characterized in that in view to ensure the air flow for cooling the moving parts there are provided at least a suction opening (11) on the bottom plate (10) and exhaust apertures (14, 15, 16, 17) on the rear wall (13) of the outer casing (1) of the apparatus housing the fan-heater unit, as well as at least an electric fan (12).