Prior Art The interest for automatic ventilation of buildings has increased recently, not only for economical reasons, but also for ecological reasons. More precisely this concerns the exhaustion of impure waste air from the interior of the build- ing. A usual way to provide for exhaust-air exhaustion without the help of energy-demanding fans, is simply to draw an upwardly open tube through the roof in order to attain a natu- ral draught in the ventilating system of the building. This natural draught depends on the thermology, i. e. possible dif- ferences between prevailing indoor and outdoor temperatures, as well as the negative pressure that may arise at the exhaust opening of the tube. This negative pressure is in turn depend- ent upon the wind speed squared, the size of the opening area and the turbulence of the wind in the area around the exhaust opening. For building technological reasons and precipitation technological reasons, such conduits sticking up point-wisely have a rather limited cross-section area. This is something which implies that the effect of the natural draught in the system becomes rather mediocre. Neither is the moderate exhaus- tion capacity of earlier known natural draught systems remedied in any crucial way in case the pipe sticking up from the roof is supplemented with so called wind driven exhaust fans or guide blades, inasmuch as the surfaces thereof exposed to the wind are only marginally effected.

In addition to having a limited air-exhausting capac- ity, such conduits, sticking up from roofs point-wisely and leading to a level above these, entail building technological complications and disadvantages, by the fact that the tubes require the making of holes in the large faces of the roofs.

Such making of holes is expensive and entails the risk of water- leakage in the interface between the tubes and the surrounding parts of the roof.

Objects and Features of the Invention The present invention aims at overcoming the above- mentioned shortcomings of earlier known ventilating devices operating with a natural draught and at creating an improved ventilating device. Thus, a primary object of the invention is to provide a ventilating device that, without the help of fans or other energy demanding means, accomplishes an improved ven- tilation in average. This should take place not only by a gene- ral enlargement of the total cross-section area of open air outlets in a roof, but also by utilising the kinetic energy of the wind in a purposeful way. Another object is to provide a ventilating device that does not demand the making of holes in the large-faced sheet or flake-shaped parts of a roof extending between the ridge and the eaves. Another object of the inven- tion is to provide a ventilating device which enables the designing of an aesthetically attractive roof while simultane- ously facilitating the connection of such roofings as roofing tile and profiled sheets, respectively, to the ridge of the roof. In a particular aspect the invention also aims at creat- ing a ventilating device that not only can attain a strong out- flow of exhaust air by means of the wind load, but also an automatic feed of supply air to the interior of the building, likewise only by means of a wind load. It is also an object of the invention to provide a ventilating device which is con- structionally simple and thereby cheap to manufacture and which furthermore may be installed in buildings during erection as well as afterwards.

According to the invention, at least the primary object is attained by the features defined in the characteriz- ing clause of claim 1. Preferred embodiments of the invention are furthermore defined in the dependent claims.

The invention is based on the understanding that the lowest air-pressure prevails where the flow velocity of the air is highest. The flow velocity of passing air on buildings is in average highest in the immediate proximity of the highly loca-

ted parts of the roof, in particular the ridge, in case there is one, in all essentials independent of the prevailing wind direction. By providing one or more long narrow slit openings in a central apex portion on a cover sheet with a thoroughly arched shape, occurring winds will sweep forwards along the smooth or unbroken top side of the arched sheet in relatively laminar flow patterns, which guarantee a maximum flow speed and thereby a high negative air-pressure in the slit openings. This vouches for the fact that the driving negative air-pressure which sucks waste air out of one or more exhaustion pipes from the interior of the building becomes optimum for the outlet area given.

Further Elucidation of Prior Art By US 4 903 445 an elongated cap mounted along a ridge is previously known with openings for exhaustion of waste air from the interior of a building. However, in this case the cover sheet of the cap has no openings for air exhaustion at all, neither is the sheet arched, but cross-section-wise V- shaped. The openings for air exhaustion are instead arranged in two interior, adjacent sidewalls of box-like constructions being under the cover sheet, which project towards opposite directions under the cover sheet. Therefore, no radically increased negative air-pressure in the ventilating openings by means of the wind load is attained in this case. An upwardly open gap exists, per se, between the free side edges of the V- shaped cover sheet and a side wall being further out of the individual box construction, but this gap can only be passed by turbulent, unstable air flows as a consequence of the fact that said long side wall has a marked height and forms an abrupt obstacle for laminar air movements along the roof surface. The long side wall also constitutes a considerable air resistance.

In a preferred embodiment, the ventilating device according to the invention is provided with a bottom part which is narrower than the upper, arched cover sheet, whereby upper portions of e. g., roofing tile or profiled roofing sheet, may in an advantageous way be pushed in under and covered by parts of the cover sheet. A ridge cap with the same function, i. e. with the ability to cover upper portions of roofings, is previ-

ously known earlier by US 4 322 924, but in this case the ridge cap has no ventilating effect at all. _ It should also be mentioned that SE 7909311-8 describes a roof ventilator having upwardly opening outlet openings. In this case, however, the ventilator consists of a voluminous box construction (preferred dimensions = 10 m x 3 m) which demands radical makings of holes in the sheet parts of a roof. Primarily, these roofs consist of roof on bigger indus- trial buildings.

Brief Description of the Appende Drawinqs In the drawings: Fig 1 is a perspective, exploded view showing a ventilating device according to the invention mounted on a ridge, Fig 2 is an enlarged cross-section through the device accor- ding to figure 1, Fig 3 is a schematic, first cross-section showing an alter- native embodiment of the device, and Fig 4 is a second cross-section, axially separated from the first section according to figure 3, that illustrates another section of the same device.

Detailed Description of Preferred Embodiments of the Invention The device shown in figure 1 includes an elongate cap generally designated 1 which extends along the ridge of a roof 2. The main part of this roof is covered with a roofing which is exemplified in the form of roofing tiles 3. Advantageously the cap 1 extends along the entire length of the ridge, although only a limited section of the same is visualised in figure 1.

In addition to a bottom part, in its entirety desig- nated 4, the cap comprises an upper part 5 which is in the form of an arched plate or sheet, i. e. a sheet having curved, e. g. circular arc-shaped cross-section shape. The central, apex-like portion of the sheet that is highest located in the mounted condition is designated 6. In this apex portion, a plurality of long narrow, longitudinal slits 7 are provided, located in a line after each other in the example. These slit openings 7 are separated from each other by means of transversal material por-

tions 8. In practice the cover sheet 5 as well as the bottom part 4 may be made either of sheet metal or of plastic Irre- spective of the material, the slit openings 7 may have a width within the range of 20-50, suitably 25-40 mm, while the length may vary most considerably. In an extreme case, the slit may be continuous, i. e. extend along the entire length of the upper part. In such cases the upper part is composed of two partial sheets separated by the slit, which sheets are united in a suitable way.

In the bottom part 4 of the cap at least one hole 9 is recessed to receive the upper part of a tube 10 through which waste air from the interior of the building may pass out in the open air, more precisely through the slit openings 7 in the upper part 5. With the exception of said hole 9 together with the slit openings 7, the cap composed of the bottom part 4 and the upper part 5, is in all essentials outwardly closed. In other words, the lower and upper parts together with suitable end portions (not shown) form a housing to the interior of which waste air may be led in through the exhaustion pipe 10 and then be led out through the slit openings 7.

As may be best seen in figure 2, the bottom part 4 comprises a cross-section-wise V-shaped bottom 11 which may be connected to and centred on the ridge, and which is connected to two upwardly projecting side walls 12. Furthermore, from the upper edge of each such sidewall a flange 13 extends, oriented at an angle to the sidewall. The angle between the individual sidewall and the appurtenant flange may vary, although advan- tageously attain 90°. In the shown, preferred example, the long-side edges 14 of the cover plate 5 are snap-in fastened along the free long-side edges of the flanges 13 and cover these. As may be clearly seen in figure 2, the distance between the free long-side edges 14 of the cover plate 5 is larger than the distance between the upper edges 15 (or corners) of the side walls 12. This means that the cover sheet 5 together with the flanges 13 corbel out from the two sidewalls 12 of the bot- tom part, while delimiting a space, designated 16, on each side of the cap. In these spaces 16, the upper parts of the roofings 3 may be received, these being covered by the cover sheet in a smooth way.

In the transition section between the edge portions of the cover plate 5 and the edge portions of the flanges-13, flute or valley-like sections 17 are formed that are located at a low level in relation to the flanges and the edge portions of the plate, respectively. In a similar way, flute-like sections 17'are formed in the transition section between the bottom 11 and the sidewalls 12. In order to lead away water, e. g. rain- water, eventually tending to be accumulated in these flute sec- tions located at a low level, diminutive draining holes 18,18' are arranged.

A number of axially separated head arches 19 are arranged within the cap having the purpose of supporting the cover sheet and of serving as a fastener therefor. Thus, it is shown how a number of clip elements 20 may be attached under- neath the cover plate, e. g. by means of blind rivets. These elements may be snap-in fastened on the arch to either keep the cover sheet in position by themselves or enforce the retention which exists by means of the clip connection along the long- side edges of the sheet. The individual arch 19 has two legs 21 that may be anchored on the roof by angled feet, e. g. by means of screws 22, which simultaneously serve to anchor the bottom 11 against the roof.

Although it is feasible per se to specially manufac- ture a cap with the same length as a given ridge along a roof, it is, in practice, preferred to manufacture the cap in the form of partial sections having limited standard length (e. g. within the range of 1-3 m), which are put together in situ while forming a continuous cap in which the individual partial sections communicates with each other.

Reference is now made to figures 3 and 4 which sche- matically illustrates an alternative embodiment of the inven- tion which not only permits exhaustion of waste air, but also feed of supply air to the interior of the building. In this case a partition 23 separates an upper cavity 24, positioned immediately under the cover sheet 5, from a lower cavity 25 in the bottom part of the cap. A waste-air pipe 10, which is shown in a given section along the length extension of the ridge in figure 3, leads to the upper cavity 24. A conduit in the shape of a tube 27 for supply air mounted in another section along

the ridge opens to the lower cavity 25, as is shown in figure 4. There are side openings 28 with flaps 29 in each one of the two sidewalls 12 of the bottom part. These flaps are automati- cally readjustable from a closing position to an opening posi- tion by the effect of pressing wind load. More precisely, the individual flap 29 is articulatedly connected at an upper edge to a part of the side wall surrounding the side opening 28 in order to, on one hand, automatically turn to a pendent and closing position by its own weight as long as the effect of the wind is insignificant or non-existent, and, on the other hand, be turned inwardly to an opening position when it is effected by marked wind load.

Suppose that the wind blows in a main direction from the left to the right according to figures 3 and 4. In such a case the air will pass along the arched top side of the cap in a substantially laminar flow, which is outlined by means of the arrows A. In this flow, the air has a maximum speed in the region of the highest located apex portion of the cover plate, something which means that a maximum negative air-pressure at prevailing wind force is attained in the slit openings 7. In other words, a marked, driving negative air-pressure is attained which effectively sucks up air through the conduit 10, which opens into the cavity 24 and communicates with the slit openings.

Simultaneously, however, also a by-pass of air found, designated B, occurs, which is pressed in under the cover sheet and against the flaps 29. Thus, in case the wind force is suf- ficiently strong, the flaps 29 will open, whereby the arriving out-door air is pressed into the lower cavity 25 and then down into the feed pipe 27 for the supply air. In other words, in the embodiment according to figures 3 and 4, not only an exhaustion of waste air through the pipe 26 is achieved, but also a simultaneous feed of supply air to the interior of the building through the pipe 27. In doing so, the waste-air exhaustion as well as the supply-air feed takes place by means of the wind only, i. e. without energy demanding fans.

A fundamental advantage of the invention is that it automatically utilises the energy contained in the occurring winds in order amplify or optimise the natural draught action

that is always guaranteed by means of the upwardly open exhaus-- tion pipe or pipes that are connected with the ridge cap. By the fact that the requisite outlet openings in the ridge cap extend along a great length, the total cross-section area becomes very large in comparison with the outlet area of a single tube, whereby the total driving power that is obtained by the negative air-pressure in connection with the slit open- ings becomes marked. Furthermore, the construction according to the invention makes every making of holes in the large faces of the roof unnecessary. For the observer the ventilating device is therefore masked in an aesthetically attractive way in the exemplified ridge-covering construction. The invention is par- ticularly advantageous in the embodiment shown in figures 3 and 4, in which not only waste-air exhaustion, but also supply-air feed is attained in an automatic way.

Feasible Modifications of the Invention The invention is not solely restricted to the embodi- ments described above and shown in the drawings. Thus, it is feasible to put together the bottom part of the cap by two or more parts instead of one single integrated part as is shown in the drawings. It is also feasible to permanently connect the upper part or the cover sheet with the bottom part. However, the embodiment shown, in which the detachable mounting of the cover sheet permits access to the interior of the cap, is pre- ferred. Furthermore, the bottom construction of the bottom part may be modified in various ways with the purpose of simplifying the application of the cap on roofs having different roof falls. Though it is preferred to place the cap according to the invention in the ridges in case those exist, it is also feasi- ble to apply the same in connection with other, preferably highly located roof parts. Furthermore, it is feasible to spare the particular bottom part that has been exemplified in the drawings. Thus, it is possible to directly form the sheet metal in seemed roofs having cross-section-wise arch-shaped portions, which together form an arched cap with slits, the exhaust-air pipe being drawn up in a free space directly under the cap. It should also be mentioned that a cap mounted in connection with a ridge may be connected to the roof in another way than the

one exemplified in the drawings. Thus, the cap may also be held- by external fastener devices instead of the internal devices described in connection with the embodiment examples. Concern- ing the flaps that are visualised in figures 3 and 4, these may be brought back to the starting position, not only by means of the gravity but also by means of springs.