The present invention relates to a ventilation system, particularly for stables, of the type disclosed in the Danish Patent Specification No. 150,399, i.e. a system comprising a number of air intake valves that are openable and closable in a differentiated manner. In the said specification there is distinguished between valves which, when regulated towards an open position, open relatively slowly, and other valves which during the same course initiate their opening with a certain delay, but will then be opened that much faster, such that both groups of valves will be fully open at the end of the regulation interval. It is obtained thereby that with the use of a simple control mechanism it is possible to produce an initial opening with a desirably limited opening area for achieving a high air velocity, while for an increasing need of ventilation it is possible to open for a considerably larger intake area.

This "two-step-system", however, exhibits certain drawbacks, primarily that it can be difficult or expen¬ sive to arrange for a sensor equipment that will react suitably rapidly on changed operational conditions for a correct adjustment thereto. If a need for increased ventilation is detected in the regulation range where the extra valves are influenced to initial opening, this will easily result in these valves being opened more than required, as it will take some time before the effect of the change can be detected, and in the mean¬ time the change may cause unsuitable effects.

The present invention aims at achieving such an equalization of the regulation course, by which there will be no marked adjustment jumps giving rise to the said control problems.

Such an equalization, of course, may well be obtai¬ ned with the use of an e.g. electronically controlled opening of the extra valves, but it is another purpose of the invention to provide for a very simple control system, viz. as simple as in the said known system.

On that background, also the present invention makes use of a plurality of single valves adapted so as to open in a differentiated manner, but instead of ope¬ rating with only two different control types there is used at least three different types, viz. such that in an initial phase of an opening cycle only a first group of the valves will be opened, while later on an opening of another group of valves is initiated and still later of the remaining third group of valves. It will be pos¬ sible to operate correspondingly with four or even more groups of valves to be successively actuated, but expe¬ riments have shown that already the said triple system provides for such a marked improvement of the total control of the system that this solution will be suffi¬ cient in many instances.

It should be mentioned that it is a particular aspect of the invention that the control mechanisms may be adapted in such a manner that it is easily possible to adjust the moment at which, during the course of the regulation, each of the valves changes to another drive transmission ratio. Thereby the invention can be impor¬ tant even for systems working in only two steps, as it will no longer be a condition that the relevant change is effected exactly at half the full opening.

It should be mentioned already here that the inven¬ tion also provides for the additional function that the valves in the various groups, once brought to their fully open position approximately at the same time, yet are collectively openable still further, now without any substantial differentiation. The reason for this is the recognition that normally it will be sufficient to adapt the control system to effect a real regulation during the majority of the hours and days of the year, while at the remaining days, viz. extremely hot days, there will be no real need for any regulation, but only for a very strong ventilation. For this reason it is desirable that the otherwise fully opened valves can be opened still

more and as much as possible during short periods, with¬ out this range calling for any sensitive control. This in itself, according to the invention, leads to a propo¬ sal of providing valve units that are larger than the normal units used so far.

For the invention it is significant that it has been found possible to make use of the same extremely simple control system as disclosed in the aforementioned patent specification. In that system there is used a drawbar mounted along a row of the relevant valves, this bar being reciprocable from a driving station, which, via a computer, is controlled by the sensor equipment of the system. Via local wire connections and wire pulleys the drawbar is connected to respective pull eyes on the valve plates of the different valves in such a manner that the valve plates can be swung up and down all ac¬ cording to the displacement of the drawbar. An opening of the valves is initiated by the valve plates being swung down from an upper closed position, and by a di¬ rect wire coupling between the drawbar and the valve plates there is, in principle, established a transmis¬ sion ratio of 1:1. According to the said patent, as far as one partial group of valves is concerned, the trans¬ mission is established with the ratio 1:0.5 through a pulley block system, such that these valves during the entire course of regulation are adjusted by the half of the movement of the drawbar, while the remaining valves are well operated with the transmission ratio 1:1, but initially not until the valves in the first group have reached half their full opening. This result is produced in a simple manner in that the wire connections between the drawbar and the valve plates in the second group of valves have such an overlength that they will not be operatively tightened until the drawbar has moved through a predetermined distance. Thereafter these valve plates will be opened by the ratio 1:1 with the drawbar movement, while the plates in the first valve group will

still be opened by the ratio 1: 2Luntil the valve plates reach the fully open position.

Relative to this, it is important for the present invention that is has been realized that the single valve groups should not necessarily be operated with a transmission ratio of either 1:2. or 1:1 throughout the course of regulation, as it is possible to shift between these ratios anywhere along that course. It is recog¬ nized that the ratio 1: % will involve a free sliding of the wire through the wire eyelet on the valve plate, and that it will be possible in a simple manner to terminate this sliding in any phase of the adjustment movement, viz. by providing a suitably mounted abutment on the wire, such that this abutment or widening cannot pass the eyelet of the valve plate. When this situation ari¬ ses the eyelet and therewith the entire valve plate will thereafter be drawn towards the drawbar with the trans¬ mission ratio 1:1.

Thus, when it can be chosen optionally in which phase there is shifted between the two ratios it is also possible to determine with which delay the opening of the different valves should be initiated, when it is desired that all valves should reach the said prelimi¬ nary "full opening". In the said known system the valves of the ratio 1:1 should be coupled in when the "1:l-val- ves" have reached half their opening, resulting in the said two step operation. The delay is established in using between the drawbar and the valve plates a wire which is slack from the beginning, but is tightened just when the opening is to be initiated, and in connection with the invention this arrangement can be used direct¬ ly. Only the overlength of the wire should be adapted to the relevant individual starting points, which may now be different so as to result in a two, three or plural step operation.

Also the desirable final opening to a full maximum can be achieved by a simple modification of the known

system. It will be characteristic that all the valve plates, the opening of which has been initiated with delay, will be coupled to the drawbar with the transmis¬ sion ratio 1:1 when they are brought to the provisional fully open position, while the first opened valve plates have had the ratio 4:2. all the time. In a way it could be acceptable that the drawbar in its further movement to the full maximum opening would cause a maximum open¬ ing of all the former valves, while only the latter ones would be moved further by the half of that movement. However, in this connection it is possible to use the same measure as already mentioned for changing the transmission ratio, viz. using an abutment member on the draw wire of the first opened valve plates, which will then move the last way in full synchronism with the other valve plates in the relevant situations.

In their simplest shape the said abutment members may be a simple knot on the draw wires or a bushing to be screw clamped at any place thereon, but it will be suitable to prepare the wires at the factory in such a manner that they are adapted to receive simple abutment members at different selected places. A solution may be small knots or expanded portions which may, themselves, pass through the draw eyelets, but be suitable for blocking for a stop disc inserted on the wire, such that this disc will then form an abutment against the draw eyelet.

In the following the invention is described in more detail with reference to the drawing, in which:-

Figs. 1 and 2 are perspective views of a group of valves according to the invention, while

Figs. 3 and 4 are cross sectional views thereof, and

Fig. 5 is a plan view of a draw wire belonging to the single valves.

In Fig. 1 is schematically shown three wall mounted valves of the discussed type, denoted A, B and C. Each

valve comprises a frame 2, in which is mounted an incli¬ ned valve plate 4, which, against spring action, is openable by pivoting about its lower hinge edge 6. The bottom piece of the of the frame 2 is designated 8. the plates 4 can be pulled down by means of wire pieces 10 engaging with a draw eyelet 12 on the plates.

In front of and somewhat beneath the valves there is arranged a drawbar 14 projecting from a non-illustra¬ ted control station and coupled to the wire pieces 10 in such a manner that the pivoting down and up of the valve plates 4 can be controlled by the drawbar 14 being dis¬ placed one way or the other. The wires are laid about pulleys 16 held to the bottom 8 of the valve frame. At a distance therefrom the wires are fixed to the rod 14 by means of clamps 20. So far described the system is fully conventional, a displacement of the rod 14 to the right resulting in a pivoting down of the valve plates 4, while these will be swung up by the said spring action when the rod 14 is moved to the left.

In the same manner as disclosed in DK-C-150,399 the wire 10 of one valve, C, is taken from the the pulley 16 up through the draw eyelet and therefrom down to a fixed fastening point 22 near the pulley, such that the wire can slide freely through the eyelet 12. Thereby a tackle draw is established with the transfer ratio 2:1 between the movements of the rod 14 and the eyelet 12C, and since the wire projects tightly the plate 4C will initi¬ ate its opening as soon as the drawbar 14 is moved to the right, and the plate will open with half the velo¬ city of the drawbar 14.

At another valve, A, the wire 10 is directly fixed to the eyelet 12, and the wire exhibits a certain over¬ length, though in the lower area it is kept tightened by means of a relatively weak contraction spring 24. As shown, the wire extends through a depending loop 26 between the ends of the spring 24. When the drawbar 14 is operated, what happens initially is that the wire 10

is tightened by the expansion of the spring 24, and when the rod 14 is moved further the associated valve plate 4 will then be swung downwardly with the transmission ratio 1:1. In DK-C-150,399 this is arranged in such a manner that the wire 10A is tightened when the valve C is brought into half opening, such that the valve A is brought from closed to fully open condition concurrently with the valve C being brought from half open to fully open condition. What makes this desirable is described in more detail in the specification of that patent.

In the system according to the example of Figs. 1 and 2 the valves A and C are arranged, in principle, quite as the two different valve types of the known system, but a valve B is added, having a slightly modi¬ fied drive system. As for the valve C, the wire 10B is arranged as a tackle draw with a fixed point 22, and moreover, as for valve A, there is used a wire having a certain overlength, though here less than for valve A, such that the associated loop 26B is shorter than the loop 26A. Moreover, between the fixed point 22 and the draw eyelet 12 the wire is provided with a knot or another widening 28 which cannot pass through the eyelet 12. Because the loop 26B is shorter than the loop 26A, the valve plate 4B responds to further regulation by initiating its opening with a smaller delay than the plate 4A, i.e. an intermediate opening stage has been added in the total system, such that it is possible to operate therein with the discussed, advantageous three- step operation.

The knot or widening 28 on the wire 10B is placed at a point of the wire defined by the eyelet 12 on the plate 4B reaching this place by such an angular position of the plate 4B at which the plate 4A with transmission ratio 1:1 has reached substantially the same angular position, while the plate 4C has moved further to an angular position midways between this position and the fully open position. When the widening 28B is hit by the

draw eyelet 12B the tackle operation will cease, because the wire can no longer slide through the eyelet, and as a result the further opening movement will take place with the transmission ratio 1:1, just as for the further movement of the plate 4A. When the plates 4A and 4B have reached the same angular positions and when the plate 4C has been moved further to the half of the remaining distance to full opening, then all the three valve plates, by the further regulation movement, will end up by reaching the fully open position concurrently.

Fig. 2 shows the situation in which the valve plate 4C has been moved to a little more than half its open position, while the plate 4A has just begun to open and the plate 4B assumes an intermediate position, to which it has been swung down with a certain delay, with the wire widening 28 located shortly in front of the draw eyelet 28B. After a certain further movement the widen¬ ing 28 will hit the eyelet 12, concurrently with the faster moving plate 4A having come down to the same angular position, whereafter both of these plates will be moved downwardly, almost as a single plate, which will reach the final position concurrently with the more slowly moved plate 4C.

This final position of the valve plates is shown in Fig. 3. According to the invention, however, it may be desirable that the valve plates can be moved further into the said extremely open condition, which is shown in Fig. 4, whereby it is also desirable that all the valve plates participate in this movement. The plates 4A and 4B are directly further movable with the transmis¬ sion ratio 1:1, while the plates 4C in the system will only be moved half the way, if they still operate with the ratio 2:1. This, as mentioned, may be acceptable, but nevertheless it is a preferred option to use the same measure as for the plate 4B, viz. a change of the transmission ratio from 2:1 to 1:1 at the moment the draw eyelet 12 reaches down to such a widening 28 on the

wire 10 which induces the change. In the valve unit C, therefore, this widening 28 is provided relatively close to the fixed point 22C, such that only during the very last phase of the course of opening the plate 4C will be moved with the ratio 1:1, resulting in the valve plates of all three valve types being moved fully synchronously in the range between fully open position and extremely open position .

In Fig. 5 it is indicated that the wire connections 10 may be produced as standard parts with fixture eye¬ lets 30 and with a number of small widenings 32 which may pass unobstructed through the associated draw eyelet 12, but are usable to form an axial support base for a marked widening in the form of a disc 34 laterally in¬ serted on the wire and provided with a radial slot 36 and a narrow central hole 38 enabling such an insertion and fastening. The stop disc 34, then, may be mounted at choice at either one or the other of the widenings 32, depending of the intended use for a valve B or C.

These wire members 10, which may advantageously be made as die-cast units, may well be prepared with many more widenings 32, such that the users themselves may decide which widenings should be used for determining the regulation characteristics of the single valve groups.

Alternatively, the wire may be made of cord as for shoe laces, and the disc is a plate having a countersunk middle hole; the plate is drawn onto the cord and is fixed by clamping with a pair of tongs.