Ventilators

Abstract: A canopy for use with a ventilator slot extending through a window frame has pressure differential responsive flow control means arranged to progressively close the flow passage through the canopy as the pressure differential increases, thus preventing draughts. The canopy has a body (1) with an inlet and an outlet and a bowed wall (21) therebetween. A normally straight baffle strip (26) is attached to the centre of the wall (21) and there are non-aligned apertures (25,28) in the wall and the baffle respectively. When the pressure differential between the inlet and outlet is low, the baffle is well-spaced from the wall but as the pressure differential increases the baffle (26) is bowed progressively towards the wall against the inherent bias of the strip to progressively close the flow path through the apertures.

Description: This invention relates to ventilators, more particularly but not exclusively for use in rooms with sealed windows and/or double glazing where it is desirable to provide for ventilation without having to open the window. This type of ventilation is now often referred to as "secondary ventilation" and has in recent years been achieved by the insertion into a slot cut or formed in the surrounds of windows and the like of a slot ventilator. The inner end of the slot may be left open but is usually provided with a manually operable closure or a grill while on the outer side there is often a canopy extending outwardly and downwardly from the top of the slot and providing a downwardly facing opening which may incorporate an insect screen, the canopy thus shielding the slot from the ingress of rain and also dust and dirt. It has been found that if the closure, when provided, is left open during windy conditions a draught blows through the ventilator. The present invention relates to improvements in such ventilation means. There is described in DE-B-2 118 030 a canopy for use with a ventilator slot comprising an elongated housing, an elongated inlet to the interior of the housing, a rear wall having a row of apertures therethrough to provide an outlet from the interior of the housing so as to provide a flow passage path for air through the interior from the inlet to the outlet, and pressure differential control means comprising a movable baffle in the form of a strip extending lengthwise of the canopy for obturating the apertures in the rear wall and biasing means tending to move the baffle away from the apertures, the baffle being movable towards the apertures against the bias of the biasing means by a pressure differential across the wall to progressively close the flow passage through the canopy as the pressure differential increases. With the arrangement described in the said DE-B-2 118 030, air flows past the baffle across its longitudinal edges and the baffle moves in directions generally perpendicular to its plane in a converging or wedge-shaped passage to vary the area of the flow cross section through the canopy. This arrangement requires that the overall height of the passage, and hence of the corresponding dimension of the canopy is substantially greater than the width of the baffle. According to the present invention, a canopy for use with a ventilator slot comprises an elongated housing, an elongated inlet to the interior of the housing, a wall having a row of apertures therethrough to provide an outlet from the interior of the housing so as to provide a flow passage path for air through the interior from the inlet to the outlet, and pressure differential control means comprising a movable baffle in the form of a strip extending lengthwise of the canopy for obturating the apertures in the wall and biasing means tending to move the baffle away from the apertures, the baffle being movable towards the apertures against the bias of the biasing means by a pressure differential across the wall to progressively close the flow passage through the canopy as the pressure differential increases and is characterised in that the baffle includes second apertures which are at least partially out of register with the first apertures in the wall when the strip is adjacent the wall. It will be appreciated that, in constructions according to the invention, flow takes place through the apertures in the baffle. The wall containing the first apertures may be a rear wall of the canopy intended to directly overlie the outer end of the slot. The apertures may for example being the shape of rectangles. The baffle may be in the form of a strip extending generally parallel with the wall. The bias may be provided by one or more springs but preferably the strip is resilient. The strip may be secured to the wall and in contact therewith at a point along its length and diverge from the wall away from the point of anchorage. There may be abutment means on the strip or the wall or both to prevent the strip making face to face contact with the wall in order to ensure that a limited degree of ventilation will always be possible and to prevent wringing to ensure that the strip will separate from the wall when the pressure differential decreases. The invention may be carried into practice in various ways and one example of a canopy for a ventilator embodying the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a partial rear elevation of the canopy; Figure 2 is an end elevation of the canopy; Figure 3 is a cross section of the canopy on the line III-III in Figure 1; . Figure 4 is a partial horizontal longitudinal section on the line IV-IV in Figure 1; Figure 5 is a cross section similar to Figure 3 on the line V-V in Figure 4 and Figure 6 is a diagrammatic horizontal longitudinal section similar to Figure 4 but to a smaller scale and showing the whole of the ventilator canopy. As can best be seen from Figures 1 and 3, a canopy comprises essentially an elongate box which is in the form of a tube made from three components 1, 2 and 3, the first constituting the body of the canopy and providing the upper and front walls 4 and 5 of the canopy, the second providing the rear wall of the canopy and the third constituting an insect screen 7 which forms the bottom wall of the canopy. The ends of the tube are closed by moulded end pieces 8 and 9 having openings 11 for screws by which the canopy can be secured to the surface to which it is attached. The canopy has a generally downwardly facing open mouth which is closed by the insect screen 7 the longitudinal edges of the screen being retained in slots 13,14 moulded in the lower edges of the walls 2 and 1 respectively. The rear wall of the canopy is afforded by the second component 2 which is a complex moulding having a longitudinal wall 21 which is generally bow shaped in plan as can be seen in Figure 4 and is supported by upper and lower horizontal walls 22,23 interconnected by vertical walls 24 to provide a coffered effect when viewed from the rear. The bowed longitudinal wall is formed with twenty eight rectangular apertures 25. A baffle 26 in the form of a slightly flexible strip is secured by rivets 27 to the central portion of the longitudinal wall and is formed with twenty eight rectangular apertures 28 which, as can be seen from Figure 4, are generally out of register with the apertures 26 in the wall 21. In the unstressed condition of the strip 26 as shown in Figure 4, the strip is straight or flat but under the effects of differential pressure, as will be described, it is able to deflect to the position 26a shown in Figure 4 by chain dotted lines where it is adjacent to the rear wall 21 but remains spaced by a short distance from the rear wall by a stop 29. The lower wall 23 contains a low pressure slot 31 which ensures a minimum amount of ventilation at all times. It will be appreciated that Figures 1 and 4 show only one end portion of a complete canopy which may be manufactured in any convenient length. Figure 6 shows one such canopy in which a rear wall structure 2 as described is combined with a similar structure 35 which is of only half the length, the two being placed end to end within a main body 1 which is of appropriate length. Clearly, canopies of other lengths can be devised, one such being of twice the length of one rear wall structure 2 instead of only one and a half times as shown in Figure 6. Operation of the canopy is as follows. When there is a small differential pressure between the downwardly facing mouth of the canopy and the slot against which the canopy is positioned, the baffle 26 will be in the condition shown in full lines in Figure 4. Air can flow into the canopy through the insect screen 7, through the apertures 28 in the baffle 26 and then through the apertures 25 in the wall 21 and into the slot. As the pressure differential increases, the end portions or wings of the baffle 26 will tend to move against the resilience of the baffle towards the wall 21 thus increasing the resistance to air flow. When the pressure differential reaches a certain level the baffle 21 will engage the stop 29 at which stage the more central apertures 25 in the wall 21 will be substantially closed while a progressively greater but still small flow will be possible through the outer apertures. Up to this stage the flow rate through the canopy and into the slot will be at least approximately independent of the differential pressure. However, because of the stop 29, the baffle 26 cannot engage flat against the wall 21 so that there will always remain a small flow path for air through the wall 21 to provide a degree of ventilation together with the small flow possible through the slot 31. When the pressure differential again falls, the resilience of the baffle 26 will tend to move the wings of the baffle away from the wall 21 thus progressively increasing the cross section of the flow path through the canopy and into the slot until the baffle 26 returns to its unstressed position.

Claims: A canopy for use with a ventilator slot comprising an elongated housing, an elongated inlet to the interior of the housing, a wall (21) having a row of apertures (25) therethrough to provide an outlet from the interior of the housing so as to provide a flow passage path for air through the interior from the inlet to the outlet, and pressure differential control means comprising a movable baffle (26) in the form of a strip extending lengthwise of the canopy for obturating the apertures (25) in the wall (21) and biasing means tending to move the baffle away from the apertures, the baffle being movable towards the apertures against the bias of the biasing means by a pressure differential across the wall to progressively close the flow passage through the canopy as the pressure differential increases and is characterised in that the baffle (26) includes second apertures (28) which are at least partially out of register with the first apertures (25) in the wall (21) when the strip is adjacent the wall. A canopy according to claim 1 in which the wall (21) containing the first apertures is a rear wall of the canopy intended to directly overlie the outer end of the slot. A canopy according to claim 1 or claim 2 in which the first apertures (25) are in the shape of rectangles. A canopy according to any of claims 1 to 3 in which the biasing means comprises one or more springs. A canopy according to any of claims 1 to 3 in which the biasing means is afforded by the strip (26) being resilient. A canopy according to any of claims 1 to 5 in which the strip (26) is secured to the wall (21) and in contact therewith at a point along its length and diverges from the wall away from the point of anchorage (27). A canopy according to any of claims 1 to 6 which includes abutment means (29) on the strip or the wall or both to prevent the strip making face to face contact with the wall.

Inventors: BURT ARTHUR JOHN, STONEY ARTHUR, WATERS RICHARD A, BURT, ARTHUR JOHN, STONEY, ARTHUR, WATERS, RICHARD A.
Applicants: TITON HARDWARE, TITON HARDWARE LIMITED
Application year: 1991
Main classification: F24F7
IPC codes: F24F13