GB2092740A

GB2092740A - Ventilating means for a household appliance

Info

Publication number: GB2092740A
Application number: GB8202463A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-02-10
Filing date: 1982-01-28
Publication date: 1982-08-18
Also published as: AT374081B; IT1149566B; FR2499686A1; DE3104711A1; CH656186A5; FR2499686B1; IT8219525A0; BE891990A; NL8200346A; LU83934A1; GB2092740B; DE3104711C2; ATA11282A

Abstract

Ventilating means for a household appliance, especially a baking oven, comprises a fan unit (3), preferably a tangential blower, connected at its pressure side (5) to an air discharge channel (6). The fan unit (3) is also provided at the pressure side (5) with a locally fixed take-off edge (17) which, in the rotational direction of a fan wheel (11) of the fan unit, bounds the trailing edge of an air outlet opening (13) and, at a spacing from this opening, is adjoined by a boundary wall (9) of the air discharge channel (6), A shield (20) or (19') extends between the edge (17) and the wall (9). <IMAGE>

Description

SPECIFICATION Ventilating means for a household appliance The present invention relates to ventilating means for a household appliance, especially a baking oven.

In ventilation devices of that kind, particularly for baking ovens, it is desirable to keep the fan as small as possible while providing a high quantity of conveyed air and a stable and steep pressure characteristic. This is influenced by the size of the flow cross-section of the discharge channel on the pressure side of the fan. In known ventilation devices, an air outlet shaft forming an air outlet opening is provided on the pressure side of the fan, wherein the boundary walls of the discharge channel directly adjoin the outlet shaft. This results in a relatively unstable pressure characteristic and an air conveying performance which may be unsatisfactory in practice, particularly at relatively high rotational speeds of the fan wheel.

There is accordingly a need for ventilating means providing a high quantity of conveyed air and a stable and steep pressure characteristic with a small mode of fan construction.

According to the present invention there is provided ventilating means for a household appliance, the ventilating means comprising a fan unit which comprises a fan wheel rotatable in a given direction and which includes an outlet opening for air conveyed by the fan wheel, and wall means defining an air discharge duct communicating with the outlet opening, the outlet opening being bounded at its trailing side with respect to said direction of rotation by means defining a separating edge for separating entrained air from the fan wheel, and the separating edge being associated with a shield which projects away from the fan wheel and at a spacing from the outlet opening approaches a boundary wall of the discharge duct.

Due to the presence of the shield leading away from the air outlet opening in conjunction with the separating edge, it may be possible to dispose the boundary wall bounding the discharge duct on the side of the separating edge away from the boundary of the air outlet opening, so that the flow cross-section of the discharge duct can be enlarged compared with conventional ventilation devices. Preferably, the shield extends substantially radially away from the fan wheel so as to prevent recirculation of the outflowing air through pressure build-up in front of the shield. In this manner, it may be possible to obtain a stable and steep pressure characteristic of the fan unit and thereby a good conveying performance.

Preferably, the separating edge is disposed at a spacing from the fan wheel and is adjoined by a separating element which extends from the separating edge generally in said rotational direction and approaches the fan wheel. This may provide an increase in air conveying performance, in that not only a small separating edge can be used for the take-off of air conveyed by the blades of the fan wheel and for the deflection of this air to the outlet opening, but also a pressure builds up, which substantially improves the take-off effect at the separating edge, in a wedge-shaped gap formed between the separating element and the periphery of the fan wheel.

An embodiment of the present invention will now be more particularly described by way of example and with reference to the accompanying drawing, the single figure of which is a schematic sectional elevation of part of a baking oven incorporating ventilating means according to the said embodiment.

Referring now to the accompanying drawing, there is shown a housing 1 of a baking oven in which is mounted a fan unit 3 with suction side 4 and a pressure side 5. The fan unit 3 is mounted in the housing 1 in, for example, the uppermost region thereof, for example within a switch chamber 2. Aerodynamically connected to the pressure side of the fan unit 3 is a discharge channel 6 consisting of an upper boundary wall 7, a substantially cylindrical channel section 8 leading into the open, an inclined boundary wall 9, and further channel sections or boundary walls, for example 10, arranged behind the pressure side of the fan unit 3. The fan unit 3 includes a fan wheel 11 having inclined fan blades 12 and rotating in the direction of the arrow, the fan wheel functioning as a tangential blower.The pressure side 5 of the fan unit 3 includes an air outlet opening 1 3 formed by a tangential extension 14 to a casing of the fan unit, by lateral walls 1 5 and by a substantially radial air guide wall 1 6. The wall 1 6 commences at a take-off 17 and is adjoined in integral arrangement by a take-off element 18 in the form of a sheet metal part. The take-off edge 1 7 is arranged at a spacing from the outer circumference of the fan wheel 11 and the takeoff element 1 8 in rotational direction of the fan wheel approaches the outer circumference thereof so that a wedge-shaped space is provided between the element and the wheel circumference.A substantially radially extending shield 20, which adjoins the boundary wall 9 as free of gap as possible, is integrally formed as a sheet metal at that end of the element 18 opposite to the edge 17.

As indicated by dashed lines, it is also possible to provide a shield 1 9' starting directly from the edge 17, which together with the wall 1 6 provides a V-shaped profile. In this case, the edge 1 7 is brought substantially closer to the circumference of the fan wheel 11.

In operation of the ventilation device, heated air in the interior of the housing 1 of the baking oven, i.e. in the neighbourhood of the oven shell, is inducted by the fan unit 3 is arrow direction and conveyed by the fan wheel 11 to the pressure side.

A take-off of the conveyed air from the fan wheel 11 takes place at the edge 17, whilst a pressure builds up in the wedge-shaped space 19, which pressure ensures a complete take-off and deflection of the air towards the pressure side of the fan unit 3 in arrow direction. Due to the fact that the flow cross-section of the discharge channel 6, determined by the spacing a of the lower boundary wall 9 from the upper tangential wall extension 14, is substantially greater than the cross-section of the actual outlet opening 13, pressure losses are minimised, i.e. a high conveying performance and a stable and steep pressure characteristic of the fan unit 3 are provided. In this case, recirculation of the expelled air, i.e. a short-circuit between the pressure side 5 and suction side 4 of the fan unit 3, is effectively prevented by the shield 20 or 19', which directly adjoins the lower boundary wall 9.

Claims

1. Ventilating means for a household appliance, the ventilating means comprising a fan unit which comprises a fan wheel rotatable in a given direction and which includes an outlet opening for air conveyed by the fan wheel, and wall means defining an air discharge duct communicating with the outlet opening, the outlet opening being bounded at its trailing side with respect to said direction of rotation by means defining a separating edge for separating entrained air from the fan wheel, and the separating edge being associated with a shield which projects away from the fan wheel and at a spacing from the outlet opening approaches a boundary wall of the discharge duct.

2. Ventilating means as claimed in claim 1, wherein the shield extends substantially radially away from the fan wheel, is stepped from the outlet opening and adjoins said boundary wall.

3. Ventilating means as claimed in either claim 1 or claim 2, wherein the fan wheel is a tangential blower.

4. Ventilating means as claimed in any one of the preceding claims, wherein the separating edge is disposed at a spacing from the fan wheel and is adjoined by a separating element which extends from the separating edge generally in said rotational direction and approaches the fan wheel.

5. Ventilating means as claimed in claim 4, wherein the shield is connected to an end of the separating element remote from the separating edge.

6. Ventilating means as claimed in claim 5, wherein the shield is formed integrally with the separating element.

7. Ventilating means as claimed in any one of the preceding claims, wherein the outlet opening is formed as a passage defined in part by a guide wall which adjoins the separating edge and extends substantially radially away from the fan wheel.

8. Ventilating means as claimed in claim 7, wherein the guide wall and shield are provided by portions of an integrally formed metal sheet.

9. Ventilating means for a household appliance, the ventilating means being substantially as hereinbefore described with reference to the accompanying drawing.