GB2036299A

GB2036299A - Space heating units

Info

Publication number: GB2036299A
Application number: GB7926295A
Authority: GB
Original assignee: Aurora Konrad G Schulz GmbH and Co KG
Current assignee: Aurora Konrad G Schulz GmbH and Co KG
Priority date: 1978-10-06
Filing date: 1979-07-27
Publication date: 1980-06-25
Also published as: FR2437949B1; GB2036299B; FR2437949A1; HU180201B; GR67229B

Abstract

Unit for heating and ventilating utility vehicles, wherein a housing is made in the form of a one-piece plastics tub (11) with end walls (30, 31) and side walls (20, 21 Fig. 2) converging from open top (12) to a base (19), the upstream end wall (30) has the air-inlet aperture (33) with a connection (34) for a fan (35) and extends at a relatively large acute apex angle ( alpha ) to the top (12), the opposed side walls (20, 21) have inwardly projecting bracket surfaces (23) for the purpose of laterally supporting the inlet side (26) of a heat-exchanger (24), said bracket surfaces being inclined with respect to the top (12) at an acute angle corresponding to about half the apex angle ( alpha ) of the upstream end wall (30), and on the outlet side (27) of the heat-exchanger (24) the downstream end wall (31) and the top (12) form by way of approximately equal lengths a prismatic space (29) with the air- outlet aperture (17, 37). In one embodiment, an oscillating flap (70) is expediently mounted so as to be pivotable about a horizontal spindle (71) between a fresh-air inlet aperture (69) and the mouth (33) of the coupling of the fan (35), and actuates a sensor (80) which controls the fan (35). <IMAGE>

Description

SPECIFICATION Unit for heating and ventilating utility vehicles The invention relates to a unit for heating and ventilating drivers' cabs, passenger spaces or the like in utility vehicles, consisting of a housing comprising an open top with a fan arranged externally on said housing, a heat-exchanger and air-inlet and -outlet apertures, the mouth of the coupling of the fan being inclined with respect to the inlet side of the heat-exchanger.

In a heating system for large-space vehicles such as omnibuses, a known method is to arrange a housing with an air-inlet and an air-outlet underneath the floor of the passenger space, said housing being ready for building in, and wherein the air-flow produced by the fans inpinges normally on the inlet side of the heat-exchanger. It is not possible to use the heating system at other points on the utility vehicle, the more so since the housing is a substantially rectangular blockshaped metal structure which is suitable above all for building into a luggage space underneath the floor of the passenger space.

As opposed thereto, the object of the present invention is to provide a heating and ventilating unit which is capable of being adapted to the most varied uses inside the utility vehicle, and which, in spite of simple construction is designed by the maker for optimum performance on the part of the fan and heat-exchanger.

In order to achieve this object, the invention proposes that the unit more precisely explained at the beginning shall comprise a housing in the form of a one-piece plastic tub with end walls and side walls converging from the open top to a base, the upstream end wall comprising the air-inlet apertures with connections for the fan and extending at a relatively large acute apex angle to the top, the opposed side walls having inwardly projecting bracket surfaces for the purpose of laterally supporting the inlet side of the heatexchanger, said bracket surfaces being inclined with respect to the top at an acute angle corresponding to about half the apex angle of the upstream end wall, and the downstream end wall and the top forming, by way of about equal lengths on the outlet side of the heat-exchanger, a prismatic space with the air-outlet apertures.

The housing is a one-piece plastics tub, made by deep drawing, injection moulding or any other suitable process. The tub may be made of polyurethane, hard PVC, polyester or the like, with or without glass-fibre reinforcement. The tub may be stacked as a result of the end walls and side walls converging towards the base. The fan or fans, preferably of the radial type, such as transverse-flow fans, are rigidly connected to the plastics tub, so that the air-flow always impinges in the same manner on the heat-exchanger, which is likewise rigidly built in. The air-fiow encounters the inlet side of the heat-exchanger at an acute angle, which is uniformly about 500.This results in uniform impingement on the whole inlet side of the heat-exchanger, the arrangement being such that relatively little deflection is imparted to the air-flow in the region of the inlet side, and the air flow likewise has only to be deflected to a relatively small extent on the outlet side, no matter how the unit is inserted. This results from the formation on the outlet side of the heat-exchanger of a prismatic space which is bounded after the manner of a roof over the outlet side by surfaces of equal length. The stronger core-flow thus results in a fairly uniform velocity profile on the surfaces with the air-outlet apertures, which considerably reduces turbulence losses in the subsequent nozzles, pipe-lines and the like.The unit is thus designed for optimum performance, which applies both as regards the flow, since the deflection of the air-flow is under 900, and as regards the heat-transfer, since the heat exchanger always remains impinged on in the same manner over its whole surface. The fins of the heat-exchanger enable the deflection to be to a large extent free of turbulence, which additionally reduces losses as regards flow and heat-transfer. The unit is thus also suitable for part-load operation, without any excessive drop in performance being capable of being detected.

The plastics tub is of simple and compact construction so that little space is required, the more so since the fan is arranged outside the tub in space-saving fashion. However, this kind of arrangement also enables the fan to be removed and replaced, for example for maintenance operations, without any relatively large expenditure on fitting. The compact construction makes the unit suitable for heating, ventilating and air-conditioning drivers' cabs, drivers' positions, passenger spaces and the like. It may be used for heating and ventilating the windscreen, for heating the foot region of drivers' positions, for heating the central corridor of coaches, for supplying hot air to the lateral ducts of omnibuses and the like.

Furthermore, a unit for heating and/or ventilating drivers' cabs, passenger spaces or the like in utility vehicles, such as for example omnibuses, with a fan which supplies fresh and if desired ambient air, is required to be provided with at least one inlet aperture for fresh air pointing in opposition to the direction of travel of the vehicle and having behind it an oscillating flap mounted so as to be freely displaceably by dammed-up air during travel and having associated with it at least one sensor controlling the fan, if desired with a heat-exchanger and air-outlet apertures pointing into the interior of the vehicle, so that the efficiency of the oscillating flap is increased and the device is made cheaper as regards control and construction and the control of mechanicaldynamic effects during travel is made less dependent.In order to solve this problem, the invention furthermore provides for the oscillating flap to be mounted so as to be pivotable about a horizontal spindle between the fresh-air inlet aperture and the mouth of the coupling of the fan, for the sensor and a spring to be arranged in the region of the mouth of the coupling of the fan, which spring holds the oscillating flap above the mouth of the coupling of the fan in a stable inoperative position, and for the sensor to be arranged between the stable inoperative position and the mouth of the coupling of the fan.

This yields the advantage that the oscillating flap is stabilised in all three operative positions, so that flow conditions which remain the same are set up in the inlet space before the heatexchanger, which conditions are independent of any particular manner of travel, more particularly the measured speed of travel, and ensure a uniform flow velocity, at the air-outlet aperture or apertures.

Examples of embodiment of the invention are reproduced in the drawing, by way of example and are explained with the aid of the following description: Figure 1 shows the unit in side elevation; Figure 2 shows a front elevation of the plastics tub of the unit - seen from the downstream end wall; Figure 3 shows how the unit is used when fitted under the floor; Figures 4, 5 and 6 show how the unit is used when fitted at the front; Figure 7 shows how the unit is used under the roof with an air-conditioning adjunct; Figure 8 shows how the unit is used when fitted at the front with an air-conditioning adjunct; Figure 9 shows how the unit is used under the roof; and Figure 10 shows how the unit is used when fitted at the front, partly in lateral elevation and partly in section.

Referring to Figures 1 and 2, the unit 10 consists essentially of a plastics tub 11 with an open top 12 which is surrounded by a circumambient flange 13. The flange 13 may comprise an outwardly projecting margin 14 which enables a cover 1 5 to be inserted. The flange 13 is provided with bores 16, which may differ in diameter, for the purpose of fastening the cover 15, said bores also being suitable for connecting the unit 10 itself to other housings or parts of the coachwork. The cover 1 5 may be provided with air-outlet apertures 1 7 in the form of slots, connecting unions or the like.

Stiffening ribs 18, which merge into side walls 20, 21 and end walls 30, 31, are expediently moulded on to the flange 13. The two side walls 20, 21 and the two end walls 30, 31 converge from the open top 1 2 in the direction of a base 1 9 which extends substantially parallel to the top 1 2.

The two side walls 20 and 21 converge at an external angle of about 8 . Each of them has an inwardly projecting indentation 22 with a bracket surface 23 which is inclined at an acute angle of about 42 with respect to the top 12. This angle corresponds to about half the apex angle of the upstream end wall 30. A wall portion 32 extends at right-angles to the bracket surface 23 between the base 19 and the end wall 31 which points downstream. On the wall portion 32 and the bracket surfaces 23 there is a rectangular blockshaped heat-exchanger 24 whereof the lateral headers are adapted to the inclination of the side walls 20, 21. This provides enlarged regions for water connections 25 in the vicinity of the top 12.

The water pipes may be brought out from the tub 11 through the end wall 30 or one of the side walls 20, 21. The heat-exchanger 24 may also be operated with oil.

The heat-exchanger 24 has an inlet side 26 and an outlet side 27 for the air-flow. Since the heat-exchanger 24 extends substantially diagonally through the plastics tub 11, it subdivides the latter into an inlet space 28 and an outlet space 29. The two spaces 28 and 29 are compietely separated from one another by the heat-exchanger 24, and in particular a sufficient seal is provided between the lateral headers and the inclined side walls 20,21 and between the wall portion 32 and the bracket surfaces 23 without any additional sealing inserts. A sealing insert may merely be provided between the upper edge of the heat-exchanger 24 and the cover 1 5 or an adjoining wall portion.

The upstream end wall 30 of the plastics tub 11 is inclined at a relatively large acute apex angle of800 to the top 12. The end wall 30 expediently comprises rectangular air-inlet apertures 33 which are provided with connections 34 for fans 35. The connections 34 may take the form of bores, projecting studs, quick closures or the like. Corresponding connecting elements are provided on the coupling 36 of the fan 35. In the case of the example of embodiment illustrated, the fan 35 is a double-stream radial fan, two double-stream radial fans 35 expediently being used. The air-inlet apertures 33 are arranged at such a distance from the top 12 that the normal projection of the coupling 36 on to the inlet side 26 of the heat-exchanger 24 is offset in the direction of the top 12.This means that the mouth aperture of the coupling 36 is not directed perpendicular to the inlet side 26 of the heatexchanger 24, and thus likewise introduces the air-flow accelerated in the region of the base 1 9 uniformly into the heat-exchanger 24. The position of the inlet side 26 and of the heatexchanger 24 is thus adapted to the velocity profile, and the fins on the finned pipes of the heat-exchanger 24 reduce the secondary turbulence and thus flatten the air-flow which is passing through.

On the outlet side 27 of the heat-exchanger 24, the downstream end wall 31 and the corresponding part of the top 12 form the prismatic space 29 with air-outlet apertures 17, 37. The end wall 31 is as long as the remaining part of the top 12, so that the prismatic space 29 is bounded after the manner of a roof by elements of equal length. The air-outlet apertures 1 7 and 37 are substantially impinged on by the same flow velocity and by a substantially rectangular flowvelocity profile. The rectangular downstream end wall 31 and the triangular regions of the side walls 20, 21 are first of all made in closed fashion with the tub 11, but have intended breaking locations which enable the air-outlet apertures 37 to be broken out at any time.They may be provided alternatively or additionally to the air-outlet apertures 1 7 in the cover 1 5. The air-outlet apertures 37 may at the same time have connecting elements 38 in the form of pins, studs, ledges, bushes or the like for nozzles or pipe-lines.

The air-outlet apertures 37 may take the form of round perforations or rectangular holes.

Figure 3 shows the unit 10 as an under-floor heater for long-distance coaches. A grid-cage 39 is connected to the upstream end wall 30 of the tub 11, and protects the fan 35 and keeps dirt particles away. The top 12 may remain open, and the flange 13 is screwed directly under the floor 40 of the passenger space. The floor 40 has a perforation 42, leading to a duct 43 in the region of the side walls 41 of the passenger space. The duct 43 is expediently covered by an air-director element 44. in the region of the central corridor 45 there may be perforations 46 through which ambient air is continuously aspirated from the passenger space into the luggage space, and passes from the latter through the grid-cage 39 to the fan 35. The ambient air is then deflected and heated as it passes through the heat-exchange 24.

It is also possible to provide a duct, indicated at 47, between the unit 10 and the aperture 46.

Figure 4 shows the unit 10 in conjunction with a front-heater for drivers' positions in omnibuses, drivers' cabs of lorries, building machines, agricultural machines or the like. In this case, the unit 10 is integrated into a housing 48 which is arranged below the windscreen 49 behind a front wall 50. Inlet apertures 51 for dammed-up air are provided in the front wall 50. Nozzles 53 are linked via corresponding hoses 54 to the air-outlet apertures 37 in the downstream end wall 31.

Hoses may be taken from the air-outlet apertures 37 in the side walls 20, 21 of the tub 11 to foot nozzles disposed to the right and left.

While in the case of the example of embodiment according to Figure 4 the top 12 is completely closed by the cover 1 5, which may also be done by a closed housing wall, the example of embodiment according to Figure 5 provides air-outlet slots 1 7 in the cover 1 5 or in the housing wall, which slots may point in the direction of the central portion of the omnibus or the driver's cab. The air-outlet slots 1 7 may be closed from inside by a simple oscillating flap 55 which is freely pivotable in the prismatic space 29.

The oscillating flap 55 may also if desired close the air-outlet apertures 37 for the screenventilating nozzles 53. The inlet apertures 51 for dammed-up air may also be capable of being closed by a flap 56 mounted on the front wall 50.

This simultaneously enables the supply of ambient air to be controlled.

As may furthermore be seen from Figure 5, the cover 1 5 may be lengthened as far as the vicinity of the floor 40, thus covering a large inspection aperture 57 in the housing. Such an aperture may also be advantageous if a flap-box 58 is provided in the lower region of the housing 48 as shown in Figure 6, enabling ambient air and fresh air to be supplied in an accurately selectable ratio by means of an externally adjustable oscillating flap.

Figure 7 shows how the unit is used as a roofventilator for drivers' cabs. A vaporiser 60 of an air-conditioning plant is provided between the flap-box 58 and the unit 10. A part-spherical nozzle 61 may be additionally provided in the base 1 9 of the tub 11, enabling the driver to supply himself with cool air in the desired fashion. A water trap 62 may be arranged below the vaporiser 60.

Figure 8 shows the air-conditioning arrangement according to Figure 7 fitted at the front, the vaporiser 60 being arranged below the unit 10, while the water-trap 62 is disposed below the inlet apertures for fresh air and ambient air, which can be closed by oscillating flaps.

According to Figure 9, the unit 10 is let into the roof of a driver's cab, the cover 1 5 comprising at least one part-spherical nozzle 61 instead of the air-outlet apertures 17. Said nozzle may be pivoted as desired for ventilating the windscreen 49 or the driver's position. A downwardly open filter 63 may be provided at the rear of the driver's cab.

According to Figure 10, a flat rectangular oscillating flap 70 is mounted in the prismatic inlet space 28 so as to be pivotable about a spindle 71 which is guided in mutually aligned bearing bores 72 arranged in the mutually opposing side walls 20 and 21. The oscillating flap 70 is made of such a size as to be freely pivotable between the two inwardly projecting indentations 22 and past the heat-exchanger 24, but capable of completely covering the fresh-air inlet aperture 69 and all the mouths 33.

In the case of this example of an embodiment, the fresh-air outlet aperture 1 7 in the cover 1 5 can be closed by a guide-flap 77. The emerging air-flow may be deflected into a definite direction by the guide-flap 77. A plurality of air-outlet slots or the like may also be provided instead of a single air-outlet aperture 17.

The fresh-air inlet aperture 69 and each of the mouths 33 are surrounded by an elastic sealing strip 73 of approximately rectangular crosssection made of plastics foam or the like.

The oscillating flap 70 may be a profiled continuous pressing, for example of aluminium, having the spindle 71 directly moulded on to it.

Said spindle stiffens the oscillating flap 70 and also constitutes the stub-spindles which are guided in the bearing bores 72. The surface of the oscillating flap 70 facing in the direction of the mouths 33 is of planar configuration, and can dispose itself flat against the associated sealing strips 73. On the other side of the oscillating flap 70, there is a raised sealing margin 74 with a circumambient spherical cylindrical surface which is partly embedded in the sealing strip 73 in the stabilised closed position of the oscillating flap 70, as the drawing shows. The sealing margin 74 may be so directed with respect to the oscillating flap 70 by way of a supporting element 75 as to be at a greater distance from the oscillating flap 70 in the region of the bearing 71, 72 than in the region of the margin opposite to the bearing 71,72.The supporting element 75 is a continuous air-tight wall which may also be formed by a tilted margin on the oscillating flap 70. This results in a uniform sealing action over the whole periphery of the fresh-air inlet aperture 69, the oscillating flap 70 being stabilised with respect to the latter by the fact that the bearing 71, 72 is at a distance from the base 19. The centre of gravity of the oscillating flap inclined against the direction of flow is thus disposed between the sealing strip 73 and the spindle 71. The same stabilising effect may also be achieved by entirely or partly inclining the base 19 against the direction of flow, in which case it is also possible to arrange the plastics tub 11 in correspondingly oblique fashion.

A spring 76 fastened to the end wall 30 may be provided between the sealing strips 73 of two adjacent mouths 33. A plurality of springs 76 may also be provided one between each pair of adjacent mouths 33. At least one leaf spring riveted to the face wall 30 may be used instead of the helical spring 76 illustrated. The amount by which the spring 76 is deflected is such that in its relaxed state as illustrated it defines the stable inoperative position of the oscillating flap 70. In this stable inoperative position the fresh-air inlet aperture 69 and the mouths 33 are open, the sum of the cross-sections of the mouths 33 being less than the cross-section of the fresh-air inlet aperture 69.

The free arm 78 of a blade-switch 80 may likewise be arranged between the circumambient sealing strips 73 of two adjacent mouths 33, the free blade-arm 78 of said switch being in engagement in the position shown with a contact blade 79, so that the sensor or switch 80 in the feed circuit of the motors of the fans 35 is closed.

The fans 35 are expediently switched in three stages capable of selection as desired, and in which the fans 35 are operated when the oscillating flap 70 is disposed in the stabilised closed position in front of the fresh-air inlet aperture 69 or in the stable inoperative position supported by the spring 76. However, if the pressure in the inlet space 28 rises under the action of the dammed-up pressure, the oscillating flap 70 compresses the spring 76 comes into engagement with the free arm 78 and thus opens the blade-switch 80, which breaks the power supply to the fans 35. This suddenly cuts off the reverse pressure at the mouths 33, and forces the oscillating flap 70 against the sealing strips 73 and the mouths 33 by way of the planar surface.

The fans 35 are expediently thus switched off as soon as the dammed-up power exceeds the power of the fans by 10%.

A different circuit-breaker may be provided instead of the blade switch 80, and might also be arranged in one of the side walls 20,21 and controlled by a narrow side of the. oscillating flap 70. A circuit-breaker may likewise be associated with one of the free ends of the spindle 71.

Although the flap has been described in conjunction with the plastics tub 11 , which is highly advantageous in use, it is also possible to mount the oscillating flap 70 directly on the front wall 50 behind the inlet apertures 51 for dammedup air. The mouths 33 may then be arranged inside an intermediate wall extending between the front wall 50 and the cover 1 5 or a corresponding part of the coachwork. The heat-exchanger 24 may also be arranged between these two parallel walls.

Claims

1. Unit for heating and ventilating drivers' cabs, passenger spaces or the like in utility vehicles, comprising a housing with an open top, a fan arranged externally on said housing, a heat exchanger and air-inlet and -outlet apertures, the mouth of the coupling of the fan being inclined with respect to the inlet side of the heatexchanger wherein the housing is made in the form of a one-piece plastics tub with end walls and side walls converging from the open top to a base, the upstrea m end wall has the air-inlet aperture with a connection for the fan, and extends at a relatively large acute apex angle to the top, the opposed side walls have inwardly projecting bracket surfaces for the purpose of laterally supporting the inlet side of the heatexchanger, which bracket surfaces are inclined with respect to the top at an acute angle corresponding to about half the apex angle of the upstream end wall, and on the outlet side of the heat-exchanger, the downstream end wall and the top constitute by way of about equal lengths a prismatic space with the air-outlet aperture.

2. Unit according to claim 1, wherein the airinlet aperture in the upstream end wall is arranged at such a distance from the top that the normal projection of the coupling on to the inlet side of the heat-exchanger is offset in the direction of the top.

3. Unit according to claim 1 or 2, wherein the open top is surrounded by a circumambient flange comprising fastening elements for the unit itself, a cover, and guide members.

4. Unit according to claim 1, wherein the apex angle between the upstream end wall and the top is about 800.

5. Unit according to claim 1, wherein the bracket surface is inclined at an angle of 420 to the top.

6. Unit according to one of claims 1 to 5, wherein the headers of the heat-exchanger are adapted to the inclination of the side walls and water connections are arranged near to the top.

7. Unit for heating and/or ventilating drivers' cabs, passenger spaces or the like in utility vehicles, such for example as omnibuses, with a fan supplying fresh air and if desired ambient air, at least one inlet aperture for fresh air pointing in opposition to the direction of travel of the vehicle and having behind it an oscillating flap mounted so as to be freely displaceable by dammed-up air during travel and having associated with it at least one sensor controlling the fan, if desired with a heat-exchanger and air-outlet apertures pointing into the interior of the vehicle, wherein the oscillating flap is mounted so as to be pivotable about a horizontal spindle between the fresh-air inlet aperture and the mouth of the coupling of the fan, the sensor and a spring are arranged in the region of the mouth of the coupling of the fan, which spring holds the oscillating flap above the mouth of the coupling of the fan in a stable inoperative position, and the sensor is arranged between the stable inoperative position and the mouth of the coupling of the fan.

8. Unit for heating and/or ventilating drivers' cabs, passenger spaces or the like in utility vehicles, such as for example omnibuses, with a fan supplying fresh air and if desired ambient air, at least one inlet aperture for fresh air pointing in opposition to the direction of travel of the vehicle and having behind it an oscillating flap which is so mounted as to be freely displaceable by dammedup air during travel and has associated with it at least one sensor controlling the fan, if desired with a heat-exchanger and air-outlet apertures pointing into the interior of the vehicle, wherein a housing is made in the form of a one-piece plastics tub with end walls and side walls converging from an open top to a base, the upstream end wall comprises at least one mouth of a coupling of a fan and extends at a relatively large acute apex angle to the top, the opposed side walls having inwardly projecting bracket surfaces for the purpose of laterally supporting the inlet side of the heat-exchanger, which bracket surfaces are inclined with respect to the top at an acute angle corresponding to about half the apex angle of the upstream end wall, on the outlet side of the heatexchanger the downstream end wall and the top form by way of about equal lengths, a prismatic space with the air-outlet apertures, the base is provided with a fresh-air inlet aperture, the oscillating flap is mounted so as to be pivotable about a spindle between the fresh-air inlet aperture and the mouth of the coupling of the fan, the sensor and a spring which holds the oscillating flap above the mouth in a stable inoperative position are arranged in the region of the mouth, and the sensor is arranged between the stable inoperative position and the mouth.

9. Unit according to claim 7 or 8, wherein the fresh-air inlet aperture has a larger cross-section than the sum of the mouths of the couplings of the fans.

10. Unit according to any one of claims 7 to 9, wherein the oscillating flap is arranged in a stabilised closed position with respect to the fresh-air inlet aperture.

11. Unit according to claim 10, wherein the fresh-air inlet aperture, proceeding from the region of the bearing of the oscillating flap, is inclined in opposition to the direction of flow of air.

12. Unit according to claim 10, wherein the fresh-air inlet aperture is vertically directed, and the bearing of the oscillating flap is arranged at a distance from the wall or base having the fresh-air inlet aperture.

1 3. Unit according to any one of claims 7 to 12, wherein the fresh-air inlet aperture and the mouths of the couplings of the fans are surrounded by elastic sealing strip.

14. Unit according to any one of claims 10 to 1 3, wherein the surface of the oscillating flap facing in the direction of the fresh-air inlet aperture comprises a circumambient raised sealing margin with a spherical cylindrical surface, which margin is partly embedded in the sealing strip in the stabilised closed position of the oscillating flap.

15. Unit according to claim 14, wherein the sealing strip is at a greater distance from the oscillating flap in the region of the bearing of said flap than in the region of the margin opposite to the bearing.

16. Unit according to claim 13, wherein the surface of the oscillating flap facing in the direction of the mouths of the couplings of the fans is of planar configuration.

1 7. Unit according to any one of claims 7 to 16, wherein the oscillating flap is a profiled continuous pressing, preferably of aluminium.

18. Unit according to any one of claims 7 to 17, wherein at least one spring which holds the oscillating flap in the stable inoperative position wherein the fresh-air inlet aperture and the mouths are open is arranged in the region of the mouths of the couplings of the fans.

19. Unit according to any one of claims 7 to 1 8, wherein the sensor is made in the form of a bladeswitch capable of being directly controlled by the oscillating flap.

20. Unit according to any one of claims 7 to 16, wherein the oscillating flap is made of sheet aluminium or surface-protected sheet steel.

21. Unit according to any one of claims 7 to 16, wherein the oscillating flap is made in the form of a plastics injection moulding.

22. A unit substantially as herein described with reference to and as shown in the accompanying drawings.