NL2021414B1

NL2021414B1 - Air duct for a plant growing system with air deflection members.

Info

Publication number: NL2021414B1
Application number: NL2021414A
Authority: NL
Inventors: Van Nieuwenhuijzen Arjan; Thomas Van Der Helm Bob; Vermeulen Dirk
Original assignee: Certhon Build B V
Priority date: 2018-07-31
Filing date: 2018-07-31
Publication date: 2020-02-11

Abstract

The invention relates to an air duct of a pliable material, provided along its longitudinal direction with a number of a holes. The holes are defined by a generally U-shaped through cut through the wall, the cut having two opposed longitudinal sides (16,17) and a transverse side (18). The wall material extending between the flap edge (19) and the end positions (22,23) of the longitudinal sides (16,17) remains attached to the wall so that a flap (21) is formed. The flap directs the air stream exiting from the duct.

Description

Air duct for a plant growing system with air deflection members.

Field of the invention

The invention relates to an air duct of a pliable material, provided along its longitudinal direction with a number of a holes and air deflection members in its wall.

The invention also relates to a plant growing system comprising such an air duct.

Background of the invention

An air duct of the above-mentioned type is described in EP 2354696. In this document a flexible hose is described for conveying conditioned air from an air conditioning unit to different parts of a building via a tube of pliable material, such as a textile duct. In the wall of this duct, which inflates to a spherical cross-section when pressurized by the air from the air conditioning unit, a number of apertures is formed along its length, by cutting away the duct wall material. In this way through-holes are formed through which the air can exit from the duct in a sideways direction. Next to each through hole are holes to which the flap of wall material remains attached, such that this flap serves as an air deflection member, directing air from the hole at an angle. This causes the air that leaves a hole without an air deflecting flap, to mix with the air that is deflected from the hole next to it, in a mixing zone, and allows better control over the sideways outflow direction of the mixed air exiting from each pair of adjacent holes.

The known flexible air duct has as a disadvantage that the stabilization zone or mixing zone along the outside of the duct, as measured from the wall of the duct in a radially outward direction, is relatively large and extends about twice the distance between two adjacent holes. In the stabilization zone, the air stream is re-directed from the longitudinal into the transverse direction, which requires pairs of differently shaped apertures. Due to the relatively large mixing zone dimension, the known air duct is unsuitable for air treatment in a plant growing system in which compact crop is grown, such as strawberries, raspberries, or flowers such as gerbera.

The distance between adjacent holes in the known air duct is relatively large for obtaining a sufficient homogenous air mixing effect. This large spacing between the holes limits the number of holes per meter that can be applied. For blowing out a predetermined volume of air per meter, the size of the holes must be increased or multiple holes along the air duct circumference should be utilized. The use of large sized holes is disadvantageous as this leads to an increase in air turbulence. This has a negative effect on plants that are situated close to the air duct, such as compact crop, which are sensitive to drafts. The use of multiple holes along the air duct circumference provides an increase in air flow but does not allow accurate setting of the airflow direction.

Furthermore, the known air duct allows direction of air in a sideways direction only. For an upwardly directed airflow, the holes need to be placed on top of air duct. In plant growth systems, such as greenhouses or daylight free growth chambers, this space is often not available, for instance due to the presence of stacked growing trays.

Object of the invention

It is therefore an object of the present invention to provide an air duct of the abovementioned type, with which the airflow direction can be accurately controlled.

It is also an object of the invention to provide an air duct having a relatively small stabilization zone along the outside of the duct.

It is again an object of the invention in which the volume of air that is supplied by the duct can be easily varied without substantially changing the size of the holes or resorting to multiple holes along the circumference of the air duct.

It is furthermore an object of the invention to provide a plant growing system comprising an air duct that allows accurate control of the airflow conditions in a confined space.

Summary of the invention

Hereto an air duct according to the invention is characterized in that the holes are defined by a generally U-shaped through cut through the thickness of the wall, the cut having two opposed longitudinal sides and a transverse side, the longitudinal sides extending from an end position to the transverse side, wherein material of the wall between the transverse side and a flap edge that is situated at positions on the longitudinal sides at a distance from the end points, is removed and the wall material extending from the flap edge to the end positions of the longitudinal side remains attached to the wall so that a flap of is formed.

By partially removing the cutout material from each hole, an air deflection flap that covers a part of the hole, is formed for each hole. In this way, each hole is provided with an individual air deflection member and the air streams exiting from the holes can be carefully controlled, depending of the stiffness of the pliable duct material, the pressure inside the flexible duct, the length of the flaps and the dimensions of the holes that are formed.

It was observed that the distance from the outside of the air duct from which a controlled transverse flow is present, is very much smaller in the constraction according to the present invention, than it is for the air duct in the prior art. This allows the use of the air duct according to the invention in confined spaces, such as in close proximity to compact crop or flowers in a plant growing system.

As the holes in the air duct of the present invention can be placed close together, large air flows can be obtained in a controlled manner. The distance between the centers of adjacent holes according to the inventon may for instance be as small as 2 cm.

Along the length direction, multiple rows of holes at different distances from the center line of the duct may be formed, depending on the air volumes that need to be supplied. In such an embodiment using multiple rows of holes, it is possible to direct the apertures differently for different rows, such as upwardly for a row in the upper half of the duct cross-section, and downwardly for a row in the lower half of the duct cross-section.

The number of rows of holes per m or per m² may vary in order to obtain a desired local value of air flow or to compensate for presser losses along the duct and to obtain an even air flow. Alternatively or in addition, along the length of the duct, the dimensions of the holes may be varied to obtain a desired air flow at a given longitudinal position along the duct.

In addition, the production of the holes according to the invention is relatively simple as a single cutting tool for all holes can be used.

In an embodiment of an air duct according to the invention, the length of the longitudinal sides is between 1 cm and 10 cm, preferably between 2 cm and 4 cm, the length of the transverse sides is between 1 cm and 10 cm, preferably between 1 cm and 3 cm and the flap edge position is situated from the end positions at a distance of between 0.05 and 1 time the length of the longitudinal sides, preferably at a distance of between 0.3 and 0.7 times, most preferably about 0.5 times the length of the longitudinal sides.

By dimensioning the flaps that partly cover the holes in the air duct of the present invention, the air deflecting properties of each hole can be set, depending on the stiffness of the material of the hose, the prevailing pressures air flows, and an optimal air flow can be obtained.

The air duct according to the invention may be formed of a low density polyethylene (LDPE) film material, having a thickness of between 150 pm and 180 pm, or may be formed of a sheath of textile material.

For the air duct according to the invention, the distance between two adjacent holes may lie between 2 cm and 100 cm, preferably between 5 cm and 50 cm.

For obtaining an air stream that is directed upwardly or downwardly, an air duct according to the invention is provided with holes of which the longitudinal sides are oriented transversely to the longitudinal direction. It was found that the direction of the air stream in an upward or downward direction can be easily and accurately set by the orientation of the holes and flaps according to the present invention.

In another embodiment, the angle of the air flow that exits the apertures, relative to a horizontal plane is determined by making opposed longitudinal sides of mutually different lengths. This will cause the flaps to allow more air to escape along the side of the longest cut, and direct the airflow in this way.

In order to firmly secure the flaps to the wall of the air duct and to prevent the cuts forming the air deflection flaps from extending further after formation, at the end positions of the longitudinal sides a hole is provided in the wall. These holes that terminate the cut on each end, effectively prevent the cut from extending itself further in the wall material when stress is exerted on it.

The hose according to the invention is particularly suitable for use in a plant growing system comprising a conditioned environment, a growing space for plants, an air treatment unit and an air duct according to the invention, connected to the air treatment unit and extending along the growing space for directing air towards plants in the growing space. The plant growing system may be a greenhouse, a growth cell using only artificial lighting or other growing systems in which crops, flowers, mushrooms, or other plants are grown.

Brief description of the drawings

Some embodiments of an air duct according to the invention will by way of nonlimiting example be described in detail with reference to the accompanying drawings. In the drawings:

Fig. 1 shows the air duct according to the prior art,

Fig. 2 shows an air duct according to the invention,

Fig. 3 shows a plan view of the hole according to the present invention,

Fig. 4 shows a plan view of an embodiment of the aperture according to the invention having termination holes at the end of the cut,

Fig. 5 shows a cross-sectional view of an air duct according to the invention having an upward airflow direction, and

Fig. 6 shows a schematic view of a plant growing system comprising air ducts according to the present invention.

Detailed description of the drawings

Fig. 1 shows a known air duct 1 of flexible or pliable material. The duct 1 has a circular cross-section and is along its length L provided with two types of apertures 3,4; 3’,4’. Apertures 3,3’ are formed by unobstructed through holes, and apertures 4,4’ are provided with an air deflection member 5,5’ that is formed by a flap of material having the same shape as the hole. The air deflection members 5,5’ are formed by the flap of material that has been cut from the wall to form the holes and that remains attached to the wall.

Air entering into the duct 1 in the longitudinal direction Al exits in the transverse direction T via the apertures 3,3’ and 4,4’. The airflow direction of air coming from the holes 3,3’ is indicated by arrows 6 and has a component in the forward flow direction, while the direction of the air flow indicated by arrow 7, coming from holes 4,4’ is deflected towards the rear. In a mixing zone Zl, extending from the wall 2 of the air duct 1 in the transverse direction T, the air streams 6,7 mix and result in zone Z2 in an air stream along the transverse direction T. The dimensions of the mixing zone Zl are of the order of about 2 times the distance z3 between two adjacent holes 3,4; 3’,4’.

Fig. 2 shows an air duct 10 according to the invention with a number of apertures 11,12; 11’,12’, each provided with an air deflection member, or flexible flap, 13,14 of wall material that remains attached to the wall but that is of smaller surface area than the area of the apertures.

The hose may comprise a plastics film such as LDPE or may be made of a fibrous material. The diameter D of the hose may be between 10 cm and 125 cm. The distance between adjacent apertures 11,12; 11 ’, 12’ may be between 2 cm and 100 cm.

The stabilization zone Z1 in which the airflow is stabilized and redirected in the transverse direction T, is relatively small and is a few tenth of the distance z3 between adjacent holes 11,12; 1112’.

Fig. 3 shows an aperture 15 according to the invention formed by a cut in the wall material. The cut has opposed longitudinal sides 16,17 that extend from end positions 22,23 to a transverse side 18 of the cut, at a rounded corner. The material in the area 20 bounded by the transverse side 18, a flap edge 19 and the longitudinal sides 16,17 has been removed. The flap 21 bounded by the transverse sides 16,17 and the flap edge 19 remains attached to the wall of the air duct and forms a flexible air deflection member. The flap edge may be situated at positions 24,25 along the longitudinal sides 16,17 and has rounded corners. The length of the longitudinal sides 16,17 may be 3 cm, the length of the transverse side 18 may be 2 cm an the length of the flap 21, defined by the distance between end points 22,23 and the flap edge positions 24,25 may be 1.5 cm.

The dimensions of the flap 21 are designed in such a way that the air stream exiting from each aperture 10,11; 10’, 11’ is directed as accurately as possible in the transverse direction T by changing of the flap edge positions 24,25.

In the embodiment of an air duct according to fig. 4, two cut termination holes 26, 27 have been provided that prevent the cut from propagating along the longitudinal sides 16,17. The diameter of the holes 26,27 may for instance be 1mm.

Fig. 5 shows an air duct 10 in which the apertures 11,12 and the air deflection flaps 13,14 are laid out to generate an airflow in the upward direction T.

Fig. 6 schematically shows a growth chamber 30 with a conditioned environment in which growth trays 31,32,33 are placed below overhead lights 35. An air conditioning unit 36 supplies conditioned air to the air ducts 37,38 from which the air is blown in a controlled sideways direction onto the crop 39,40. Multiple layers of growth trays 3133 may be stacked one on top of the other, lighting being provided over each tray. The air ducts 37,38 may be laid out to blow air to both upper and lower levels of growth trays by orientation of the apertures in the manner shown in fig. 5.

The air ducts according to the invention may be used for blowing air onto compact crop but may also be used in combination with plants that allow for larger stabilization zones, such as for instance tomatoes.

Claims

Conclusions

An air duct (10) of a flexible material, along its longitudinal direction (L) provided with a number of holes (11, 11 ', 12, 12') and air deflecting members in its wall, characterized in that the holes (11, 11 ' 12, 12 ') are defined by a substantially U-shaped cut through the wall, the cut having two opposite longitudinal sides (16, 17) and a transverse side (18), the longitudinal sides extending from an end position (22, 23) to the transverse side (18), with material of the wall between the transverse side (18) and a flap edge (19) located at a position (24, 25) on the longitudinal sides (16, 17) at a distance from the end positions (22.23) has been removed and the wall material extending between the flap edge (19) and the end positions (22.23) of the longitudinal sides remains connected to the wall thereby forming a flap (21).

Air duct (10) according to claim 1, wherein the length of the longitudinal sides (16, 17) is between 1 cm and 10 cm, preferably between 2 cm and 4 cm, the length of the transverse side (18) between 1 cm and Is 10 cm, preferably between 1 cm and 3 cm and the position of the flap edge (19) is positioned at a distance from the end positions (22,23) of between 0.05 and 1 times the length of the longitudinal sides (16, 17), preferably at a distance of between 0.3 and 0.7 times, most preferably about 0.5 times the length of the longitudinal sides.

Air duct (10) according to claim 1 or 2, wherein the distance between two adjacent holes (11, 12; 11 ", 12") is between 2 cm and 100 cm, preferably between 5 cm and 50 cm.

Air duct (10) according to one of the preceding claims, wherein the longitudinal sides (16, 17) of the holes are oriented transversely to the longitudinal direction (L).

Air duct (10) according to one of the preceding claims, wherein the length of the opposite longitudinal sides (16, 17) is different from each other.

Air duct (10) according to one of the preceding claims, wherein a hole (26,27) is provided in the wall at the end positions (22.23) of the longitudinal sides (16, 17).

A plant growth system (30) comprising a conditioned environment, a growth room for plants, an air treatment unit (36) and an air duct (37, 38) according to the invention, connected to the air treatment unit (36) and extending along the growth space for guiding air to plants (39.40) in the growing room.