WO1998030086A1

WO1998030086A1 - Cattle shed ventilation system with air intake valves, and such valves for such systems

Info

Publication number: WO1998030086A1
Application number: PCT/DK1998/000014
Authority: WO
Inventors: Holger Eriksen; John L. Christensen
Original assignee: Skov AS
Current assignee: Skov AS
Priority date: 1997-01-09
Filing date: 1998-01-09
Publication date: 1998-07-16
Anticipated expiration: 1999-07-09
Also published as: DK2397A; AU5312898A

Abstract

In an intake valve with pivotable damper (4), an air baffle-plate (10) lying in front of said damper (4) must be active only in a regulation area near the closed position. To achieve this in a cheap and advantageous manner, use is made of a spring system with a weak spring (16) which holds the baffle-plate in the active position against a stop (14), and with a stronger, pre-stressed spring (24, 26) which is connected to the damper (4, 22) so that, in a centre-most regulation area, this spring acts as a drawbar for the swinging down of the baffle-plate to a lying, passive position, after which in a regulation area towards full opening the damper stretches the pre-stressed spring without hereby influencing the passive position of the baffle-plate. The settings of the baffle-plate will be controlled in a clearly-defined manner, without any floating positions between the two opposing spring influences.

Description

Cattle shed ventilation system with air intake valves, and such valves for such systems.

The present invention concerns a cattle shed ventilation system with air intake valves, and also such valves for such systems. It is widespread practice that use is hereby made of wall-mounted intake valves configured in a box-like manner as rectangular tubes with a pivotable damper which from an outer lower-edge area ex- tends at an angle upwards and inwards for closing against an upper seating-edge area at the inner end of the box or the rectangular tube. The damper is spring-loaded to swing upwards towards this closed position, and thus in a simple manner can be disposed for controlled opening merely by being connected with a draw-string, by means of which it can be drawn down to provide a smaller or larger opening .

With the system under consideration, there will normally be involved a whole series of such intake valves which are controlled from a common regulation station, i.e. by means of a horizontal and longitudinally-movable drawbar extending from said valves, said bar being connected at the individual intake vales to the above- mentioned draw-string, which from an extent lengthwise with the bar thereafter extends upwardly for connection with the damper via a reversing roller at the lower edge of the inside end of the box or the rectangular tube. A displacement of the drawbar in one direction will hereby result in a controllable opening of the dampers, which can also be closed in a controllable manner by displacement of the bar in the opposite direction.

Normally, the air intake is established by creating a certain underpressure in the cattle shed by means of roof-mounted extraction fans which can work with requirement-controlled effect, and whereby it is relevant to regulate the intake valves in order to achieve the desired admission characteristic of the sucked-in air. It is herewith of importance that the system works with angularly-disposed, pivotable dampers, in that with a slight degree of opening these will have an upwardly-controlling influence on the intake air, which is advantageous for a good distribution, of air in the cattle shed when operating with a low air exchange in connection with cold external air.

For an optimised function of the relevant ventilation systems, advanced, computer-based control systems have already been established which can determine the exchange of air depending on the temperature conditions. However, conditions can arise in the individual installations which make it desirable to effect a mechanical regulation of the reaction of the dampers to arising setting influences. Examples of this can be seen in DK-C- 150,399 and EP-0678185, both of which deal with differen- tiated exchange conditions between the horizontal displacement of the above-mentioned drawbar and the string which connects this with the individual dampers. Regard can hereby be paid to conditions other than those which can be accommodated by the computer control, the extent of which does not, after all, replace the very simple mechanical, common control of the individual dampers via the said drawbar. Extra regulation possibilities can be achieved by altering the transfer characteristic between the displacement of the drawbar and the associated verti- cal swinging movement of the individual dampers, or merely just one of said dampers.

While the basic control of the dampers for the establishing of special opening characteristics can thus take place partly via a main control and partly via indi- vidual couplings, circumstances will still continue to arise with which the regulation is not optimal, especially with regard to the admission pattern of the intake air, all depending on whether the intake valve is under influence of a higher or lower outer wind pressure.

In light of this, it has already earlier been found to be desirable to provide the intake valves with a pivotably-disposed baffle plate outside the damper, and in such a control connection with this that with greater degrees of opening of the damper the baffle-plate assumes a substantially horizontal and herewith ineffective position, while at lower degrees of opening it assumes more steeply-sloping positions in which it forms a shield against a completely free induction of air from the out- side, though without limiting the opening degree of the valve, i.e. it forms a kind of "dynamic shield". Also in its completely horizontal state the baffle-plate has a certain height or thickness which is so much less than the height dimension of the intake valve that in no way will it obstruct a free through-flow of air when this is what there is most use for, i.e. with fully open valve, regardless of whether there hereby arises a contribution from an external wind pressure.

In principle, it is a simple technical task to arrange a mechanical control connection between the damper and the baffle plate such that the latter will turn between the vertical and the horizontal position depending on the movement of the damper from the fully closed to fully open position, see e.g. NO-C-6298. How- ever, in practice this task is not quite so simple, in that the problem will involve requirements concerning a special coupling characteristic, e.g. so that the baffle- plate is held ineffective during a first phase of the opening of the damper, while immediately thereafter in the course of regulation it is turned towards its maximum blocking position and then thereafter to its horizontal position, all with the object of establishing a regulation sequence which manifests itself by more or less even frequency of the relationship between the underpressure in the cattle shed and the associated change of air. Experiments with reasonably simple solutions such as pivot joint connections have not hitherto been successful.

With the present invention, however, the possi- bility has been realised of achieving the desired result by using a simple spring system with partially loose coupling to the baffle-plate, i.e. such as that disclosed in claim 1.

Reference will now be made to the drawing, which shows a preferred embodiment of the invention, in that fig. 1 is a schematic perspective view of an intake valve according to the invention, fig. 2 is a more detailed side section thereof, seen with the damper in the closed condition, figs. 3-7 are corresponding side views for the illustration of the function at increasing degrees of opening, and fig. 8 is a graphical representation of a regulation sequence.

The valve shown in fig. 1 has a rectangular, tubular housing 2 intended for building into the wall of a cattle shed with the shown right-hand end facing inwards. Near the outer end, right down at the bottom of the hous- ing, there is pivotably-mounted an inclined damper 4 which closes against the upper edge 6 of the housing. In a manner not shown, the damper 4 is spring-loaded towards its closed position, from which it can thus be swung down by means of a draw-string 8 which, in a manner not shown in more detail, is connected to a drive-station which can activate a larger number of such intake valves.

The damper 4 in fig. 1 is shown in a slightly open position, and it will be seen that in front of the closing area there is a plate 10 mounted upright inside the housing. The immediate object of this plate, which is the said air baffle plate, is to reduce the effect of an external wind pressure with regard to the passage of air through the valve, otherwise at the lower degrees of opening this could cause disturbances in the automatic regulation of the ventilation. At higher degrees of opening, this situation will gradually be of less significance, and eventually the baffle effect on the inflow of air will be directly undesired, i.e. when a high exchange of air is required anyway.

In connection with the invention it has shown that the baffle-plate also more generally offers appreciable advantages, in that with qualified control it is made possible to minimise the irregularities and hunting which often arises in the relevant systems in connection with changes in the ventilation conditions. This is discussed in more detail below.

In light of this it is desirable that the baffle-plate 10 can be turned to the horizontal as a well- controlled function of the opening of the damper 4, although not as a linear function, and the plate 10 is therefore pivotably-disposed around a horizontal axis by means of axle journals 12. In fig. 1 it is also shown that the plate 10 is held in its vertical position by be- ing drawn up against a fixed stop 14 by means of a spring 16 which is secured to an edge flange standing slightly inwards at the outer end of the housing 2. The parts mentioned above are also to be found in fig. 2, where the said edge flange is indicated by reference figure 18.

In fig. 2 the damper is shown completely closed, and here it will be seen that the baffle-plate 10 is not completely vertical but sloping slightly inwards as a consequence of a lower projection 20 on the plate 10 being pressed slightly outwards by contact against the closed damper 4. This is not a main characteristic of the principle, but with the preferred embodiment it has been found desirable to allow the baffle-plate 10 to exrend so far downwards that when the damper is in its closed position, the baffle-plate will lie against this and hereby impede a desirable upflow of air along the damper 4 at the very first slight opening of said damper. Upon such a slight opening, it is desirable that the inducted air is projected inwards and upwards in the cattle shed, and this effect is promoted by making it possible for the influx of air to flow from the lower end of the damper 4. In this position, the spring 16 will be slightly stretched, and therefore at the start of the opening of the damper 4 the stop-face 20 will be moved forwards during the outward- swinging of the upper end of the plate 10 until this abuts against the stop 14 in a vertical posi- tion of the plate 10, see fig. 3. The plate 10 is now held with a certain pre-stressing against the stop 14, and with the immediately subsequent, further opening of the damper 4 the plate 10 will remain passively in this vertical position. As shown in figs. 2 and 3, between the upper end of the plate 10 and a bracket 22 on the outwardly-facing side of the damper 4, a connection is established in the form of two helical springs 24 and 26 which are hinged together in a freely pivotable manner in a hook or eye assembly 28. These springs are completely passive during the further opening of the damper 4, which takes place from the position shown in fig. 3, but during this opening, when the bracket 22 is, of course, moved away from the top of the plate 10, the two springs 24 and 26 will be straightened out to a position in extension of each other, which is shown in fig. 4. These springs are mounted with an appreciable pre-tension, i.e. so that as a collective tractive element they will work as a drawrod opposite the spring 16, and consequently upon further opening of the damper 4 they will forcibly turn the plate 10 under the stretching of the spring 16. During this further opening procedure, the plate 10 is thus made to swing down through an intermediate position as shown in fig. 5 to an end position shown in fig. 6. In this end position of the plate 10, the projection 32 at the lower edge of the plate will abut against a fixed stop 30 in the housing 2, so that the damper 4, under the stretching of the springs 24 and 26, can hereafter be drawn further down towards a fully open position, cf. fig. 6. without the baffle-plate 10 hereby being turned out of its horizontal position, in which it is now quite ineffective with regard to the blocking of the flow of sucked-in air. With full opening of the damper as shown in fig. 7, the spring pair 24,26 will be stretched to the maximum.

Hereafter, with corresponding closing of the damper 4, corresponding movements will occur in the reverse order. The system will constantly be in balance, so that the movements take place in a well-defined manner, also with smaller up and down-regulations in part sections of the overall regulating area. It is important in practice that the extended spring system 24, 26 works precisely as a fixed drawbar opposite the spring 16, so that there does not arise a regulation phase in which the plate 10 is flexibly influenced from both sides, since in such case the plate 10 will not be under clearly-defined control . The movement characteristic for the air baffle- plate 10 can be regulated to a wide extent by the choice of positioning and the height of the plate and the length of the springs used, whereby in a simple manner it is possible to adjust the function to suit individual in- stallations. Experiments have shown that it is an advantage to adjust the system in such a way that, with an example curve as shown in fig. 8, it is possible to achieve an evenly varying relationship between the performance of the ventilation system and the underpressure prevailing in the cattle shed, in that in an intermediate area, where an external wind pressure could have a disturbing effect, the system can hereby work with a relatively high underpressure and consequently a relatively strong air damping. This means that the intake of air is controlled from within in the critical area, which is all -important , and that the controlling of the system can herewith be effected with high precision without unnecessary hunting. This is an appreciable general advantage, regardless of the effect of the external air. It is not necessary for the spring system 24,26 to comprise two springs, merely providing that the system is arranged to start functioning after a certain opening of the damper, and thereafter to overcome the tension from the spring 16 for graduated swinging of the baffle- plate 10 over a certain area of regulation, so that in the individual installation the aim will be to achieve a reasonably even course for the curve cf. fig. 8. The kind of means used to co ntrol the swinging movement of the damper 4 is not decisive for the invention.

Claims

C L A I M S

1. Air intake valve in or for controlled ventilation systems, especially in cattle sheds, and of the kind which have a tubular valve housing with a pivotable damper which from an outer lower-edge area extends at an angle upwards and inwards for closing against an upper seating-edge area at the inner end of the preferably rectangular valve housing tube, in which there is also housed a pivotable air baffle-plate for dynamic damping of in-flowing air in an upper area of the valve tube in front of the closed damper, said baffle-plate being in control connection with the damper such that when the damper begins to swing downwards, the baffle-plate as- sumes a steeply-standing position, while in a centre-most regulation area it is swung to a lying position upon further swinging down of the damper, after which the baffle- plate remains in the lying position during further swinging of the damper in a regulation area up towards full opening, c h a r a c t e r i z e d in that said control connection is configured in such a manner that between the damper and an upper swing-edge on the baffle-plate there is inserted a pre-stressed spring coupled with such a free engagement that in the regulation area close to full closing the damper is freely pivotable without stretching the spring, while the baffle-plate is independently spring-loaded for assuming its steeply-standing position while drawn against a fixed stop, said pre- stressed spring being arranged in such a way that in said centre-most regulation area it forms a stiff drawbar connection between the relevant elements, in that it is sufficiently pre-stressed to be able to overcome the spring power which acts on the baffle-plate, and hereby to swing the baffle-plate to its lying position against a stop- face, while from the position corresponding hereto the damper is further pivotable in the regulation area towards full opening under extension of the pre-stressed spring .

2. Intake valve according to claim 1, c h a r a c t e r i z e d in that a distance piece is inserted between the damper and the lower swing-edge of the baffle- plate, which in the regulation area near to the closed position ensures that a distance is maintained with a slight swinging-out of the baffle-plate from said fixed stop .

3. Intake valve according to claim 1, c h a r a c t e r i z e d in that the pre-stressed spring is configured as two elements which are mutually connected in a freely hinged manner.