GB2117982A

GB2117982A - Improvements in the cooling of motors driving extraction fans

Info

Publication number: GB2117982A
Application number: GB08307406A
Authority: GB
Inventors: Pierre Avril
Original assignee: Jeumont Schneider SA
Current assignee: Jeumont Schneider SA
Priority date: 1982-03-18
Filing date: 1983-03-17
Publication date: 1983-10-19
Also published as: IT8347930A0; NL8300894A; GB8307406D0; GB2117982B; LU84695A1; IT1166442B; BE896199A; FR2523696A1; FR2523696B1; DE3309643A1

Abstract

The cooling of a driving motor (2) of a turbine (1) which is used as an extraction fan for evacuating heated fumes or smoke from an enclosed area, is provided by a frusto-conically shaped hood (7) which is supported on a plate (3) by means of an annular cage (8) carrying a grid (9). The lower peripheral section of the hood (7) together with an annular downwardly inclined extension (14) of the support plate provide a throttle which together with the flow of heated fumes or smoke through an annular cage (14) from the turbine (1) cause a venturi effect to occur, the resulting drop in pressure at the throttle causing the flow of cooling air through the hood (7). The upper part of the hood (7) has a neck (13) and is covered by a grid (10) to provide an inlet for cooling air to the motor (2). <IMAGE>

Description

SPECIFICATION Improvements in the cooling of motors driving extraction fans The present invention relates to a method of and apparatus for cooling the driving motor of a turbine which is used as an extraction fan for evacuating heated fumes or smoke from an enclosed area.

A number of different devices provided for obtaining the evacuation of heated fumes or smoke at the end of a conduit such as that belonging to a kitchen, a house, a shop or a loft, are already known. These utilize a motor driving a turbine constituting a fan-blower or ventilator, which sucks in aspires and evacuates the hot fumes or smoke either vertically upwardly, or laterally into the atmosphere.

These known types of devices operate satisfactorily when they function under normal conditions. However, in the event of an abnormal elevation of the temperature of the fumes or smoke, for example in the case of fire, where this temperature may reach 4000C and be maintained at this temperature for a period of time, the motor may become overheated with the result that irrepairable damage to the motor or the turbine may occur.

A number of previous attempts have been made to remedy this convenience; such as increasing the dimensions of the motor, strengthening of its protection against the effect of heat, the addition of an auxilliary cooling device.

All the above solutions involve construction complications, supplementary elements, and an increase in the cost of the apparatus. In our French Patent Specification No. 2,497,299 there is disclosed a device which overcomes the above referred to disadvantages.

In the disclosure in French Patent Specification No. 2,497,299, there is provided a temperature sensing device which senses the temperature of the heated fumes or smoke extracted by the turbine. Means are also provided to raise the hood of the motor 2 to permit an increase of cooling air inside the hood so as to cool the motor. In the event of a fire, the temperature sensitive means causes the lifting of the hood surrounding the motor in order to provide improved cooling thereof and thus prevent it being damaged due to excessive heat from the fumes or smoke of the fire.

Such mechanically operated means for lifting the hood are complicated and liable to malfunction. Accordingly, it is an object of the present invention to provide improved cooling of the motor without the need of using mechanical moving parts.

According to one aspect of the present invention, there is provided a method of cooling the driving motor of a turbine which is used as an extraction fan for evacuating heated fumes or smoke from an enclosed area, wherein said method consists in causing said extracted fumes or smoke which are ejected perpendicularly with respect to the axis of the motor and turbine to provide a venturi effect on air in the lower part of a hood surrounding said motor thereby causing due to pressure difference cooling air to flow through said hood from a narrow upper end to a throttle section formed at the lower end of said hood whereby said motor is cooled with air at atmospheric temperature.

According to another aspect of the present invention there is provided apparatus for cooling the driving motor of a turbine which is used as an extraction fan for evacuating heated fumes or smoke from an enclosed area, said apparatus comprising: a hood for the motor having an opening at the upper end thereof to permit the flow of air from the atmosphere; an annular opening at the lower end thereof being formed as a throttle member and opening into the passage of the extracted heated fumes or smoke from the turbine; the flow of extracted fumes or smoke causing a venturi effect at the throttle member to effect a reduction in pressure thereat below atmospheric pressure thereby causing cooling air to flow into the hood from the upper end thereof in order to cool the motor.

By means of the above method and apparatus the previously required results furthermore exhibit the important advantage that they permit a substantial reduction in the number of members of the apparatus and considerable simplification in respect of the design and construction thereof.

The present invention will now be described in greater detaii by way of example with reference to the accompanying drawings wherein: Figure 1 is a diagrammatic cross-sectional view of one preferred form of apparatus for cooling the driving motor of a turbine which is used as an extraction fan for evacuating heated fumes or smoke from an enclosed area; and Figure 2 is a part diagrammatic cross-sectional view of a modified form of the apparatus shown in Figure 1.

Referring to Figure 1, a turbine 1 constituting a fanblower is driven in known manner by a verticalaxis motor 2. The motor 2 is secured to a plate support member 3 carried by an annular cage member 4. The annular cage member 4 is secured to a bracket 5 located at the end of an evacuation conduit (not shown).

A narrow gap 6 is formed between the bracket 5 and the turbine 1 in order to take into account possible deformations of these two members under the influence of heat when the fanblower is required to evacuate the hot fumes or smoke caused for example by a fire.

The motor 2 is protected by means of a substantialty frusto-conical shaped hood 7, which is secured to the annular cage member 4 by means of a second annular cage member 8. These annular cage members 4 and 8 are provided with a grid plate 9. The hood 7 is itself provided with a grid plate 10 at the open upper portion constituting the smaller base 11 of the frustum of the cone. The larger base has an annular opening 12 exteriorly of the annular cage member 8.

Under these conditions, due to the shape and positioning of the hood 7 and of the annular cage members 4 and 8, a permanent air flow penetrating through the grid plate 10 of the hood 7 and flowing out through the grid plate 9 as indicated by an arrow A effects the constant cooling of the motor 2. In this example, it will be noted that a constriction or neck 13 of the hood 7 is provided near the small base 11 of the cone frustum in order to increase the rate of flow of cooling air in the vicinity of the motor 2.

It will be seen from Figure 1, that as the heated fumes or smoke extracted by the turbine 1 follow the path of the arrow B, they cause at the annular opening between the lower end of the hood 7 and a slightly downwardly inclined plate 14 being an extension of the plate support member 3, a reduction in air pressure below atmospheric pressure due to the venturi effect. This reduction in pressure at the throttle point defined between the lower end of the hood 7 and the extension plate 14, causes air to be sucked in through the grid plate 10 thus causing a flow of cooling air passed the motor 2.

Referring now to Figure 2, in the modified form the shape of the upper portion of the hood 7 is different. In this modified form the hood 7 is covered by a curved lid 1 5 constituting a lantern, a side portion 1 6 of which is latticed to ensure the air flow previously referred to with respect to the embodiment shown in Figure 1. It will be appreciated that in this embodiment the initial flow of air into the hood 1 7 is radially inwards before being deflected downwards onto the motor 2.

Claims

1. A method of cooling the driving motor of a turbine which is used as an extraction fan for evacuating heated fumes or smoke from an enclosed area, wherein said method consists in causing said extracted fumes or smoke which are ejected perpendicularly with respect to the axis of the motor and turbine to provide a venturi effect on air in the lower part of a hood surrounding said motor thereby causing due to pressure difference cooling air to flow through said hood from a narrow upper end to a throttle section formed at the lower end of said hood whereby said motor is cooled with air at atmospheric temperature.

2. A method according to Claim 1, wherein the cooling air sucked in at the upper end of the hood initially flows in a direction substantially parallel to the axis of the motor.

3. A method according to Claim 1, wherein the cooling air sucked in at the upper end of the hood initially flow in a direction substantially perpendicular to the axis of the motor.

4. Apparatus for cooling the driving motor of a turbine which is used as an extraction fan for evacuating heated fumes or smoke from an enclosed area, said apparatus comprising: a hood for the motor having an opening at the upper end thereof to permit the flow of air from the atmosphere; an annular opening at the lower end thereof being formed as a throttle member and opening into the passage of the extracted heated fumes or smoke from the turbine; the flow of extracted fumes or smoke causing a venturi effect at the throttle member to effect a reduction in pressure thereat below atmospheric pressure thereby causing cooling air to flow into the hood from the upper end thereof in order to cool the motor.

5. Apparatus according to Claim 4, wherein said hood is substantially frusto-conical in shape and is provided with an annular cage which secures it to a plate which supports the motor, the cage being provided with a grid through which cooling air can flow on its way to the throttle.

6. Apparatus according to Claim 5, wherein the upper part of the frusto-conical hood has a neck portion and its smaller upper base is provided with a grid defining an air intake for the cooling air to the motor.

7. Apparatus according to Claim 5, wherein the frusto-conical hood is covered by a curved lid and has a side position near the upper end thereof which is latticed.

8. Apparatus according to any one of the preceding Claims 5 to 7, wherein the support plate has an annular extension which is downwardly inclined to form together with the lower peripheral wall of said hood, the throttle member which provides the venturi effect on air within the hood.

9. The method of cooling the driving motor of a turbine substantially as herein described with reference to the accompanying drawing.

10. Apparatus for cooling the driving motor of a turbine substantially as herein described with reference to and as illustrated in the accompanying drawing.