GREENHOUSE AS WELL AS ROOF ELEMENT FOR SUCH A GREENHOUSE HAVING INCREASED LIGHT TRANSMISSION

Abstract: The invention relates to a greenhouse (1) provided with a roof element (2) having a multiplicity of transverse ribs (12, 13, 14, 15) or pyramids uniformly distributed over the roof element. The roof element can be constructed double-walled as a hollow-core sheet from transparent plastic and can comprise a base sheet with the rib-shaped or pyramid-shaped roof surfaces fixed thereon. The light yield in a horticultural greenhouse can be increased by means of the roof elements according to the present invention.

Description: Greenhouse as well as roof element for such a greenhouse having increased light transmission The invention relates to a greenhouse having a transparent roof construction with a longitudinal direction and a transverse direction located peφendicularly thereto, having vaπous pairs of first roof surfaces in succession in the transverse direction, the first roof surfaces of a predetermined pair running at an angle with respect to a hoπzontal from a base edge oπented in the longitudinal direction of the greenhouse to a common apex The invention also relates to a roof element for use in such a greenhouse It is known from the publication entitled "Second International Symposium on Models for Plant Growth", Environmental Control and Farm Management in Protected Cultivation, number 456, March 1998, to provide horticultural greenhouses with roof surfaces in succession in the transverse direction which run in the shape of a point towards an apex For angles to the hoπzontal of greater than 45° the light transmission for radiation which is incident peφendicularly on the greenhouse is found to increase substantially This is particularly important in horticultural greenhouses since one per cent more light yield results in approximately one per cent more yield of crops An aim of the present invention is to provide a roof construction of the above- mentioned type, provided with a quantity of pairs of roof surfaces which are laid in contact with one another and come together in an apex, the light transmission being increased To this end the roof construction according to the present invention is characteπsed in that the greenhouse is also provided with pairs of successive second roof surfaces in the longitudinal direction, which second roof surfaces run at an angle with respect to the hoπzontal from a base edge oπented in the transverse direction of the greenhouse to a common apex It has been found that a zigzag or πbbed pattern of the roof surfaces extending in two peφendicular directions is able to increase the light yield by 10%-20% compared with roof constructions which are of zigzag construction only in the transverse direction In a first embodiment the pairs of roof surfaces form pyramids which are joined to one another along their sides to give a continuous roof construction In another embodiment of a greenhouse according to the invention the pairs of first roof surfaces are in contact with one another along edges at the apex, w herein base edges and the edges at the apex of the pairs of first roof surfaces extend parallel to one another in the longitudinal direction, wherein the pairs of second roof surfaces are in contact with one another along edges at the apex and wherein the base edges and the edges at the apex of the second pairs of roof surfaces extend parallel to one another from a base edge of a first roof surface to the edge at the apex of the first roof surface concerned. By this means successive transverse ribs are formed in the longitudinal direction of the greenhouse. It is preferable to construct roof elements with a zigzag pattern double-walled as a hollow-core sheet so that, on the one hand, adequate strength and insulating effect of the roof construction is obtained whilst, on the other hand, the light transmission is increased. The double-walled roof elements comprise a base surface made of, for example, polycarbonate with a thickness of 0.8 mm on which a zigzag-shaped sheet with ribs approximately 20 mm high is fixed. Preferably, the double-walled roof element is made in one piece. The roof elements can be of modular construction and are provided with coupling means for joining to similar roof elements. A greenhouse according to the present invention and a roof element will be explained in more detail below with reference to the appended drawing. In the drawing: Figure 1 shows a diagrammatic, perspective view of a roof with a roof construction that is in zigzag form in the transverse direction and the longitudinal direction, Figure 2 shows a diagrammatic, perspective view of a roof construction formed from a series of pyramids, Figure 3 shows a cross-section of a double-walled roof element in the form of a hollow- core sheet according to the present invention, Figure 4 shows an alternative embodiment of a double-walled roof element in the form of a hollow-core sheet according to the invention, Figure 5 shows a double-walled roof element formed by a series of pyramids, and Figure 6 shows two roof elements joined to one another by means of coupling means. Figure 1 shows a greenhouse 1, such as, for example, a greenhouse of the Venlo type having a transparent roof construction 2. The roof construction 2 is supported on uprights 3 and horizontal lattice girders 4, which are shown here diagrammatically only. The height a of a greenhouse as shown in Figure 1 is, for example, 4 m, whilst the width, d, in the transverse direction D, is 8 m for a length in the longitudinal direction L of, for example, 100 m. The roof construction 2 comprises pairs of first roof surfaces 5, 6; 7, 8, which run from a base edge 1 1 , 1 1 ', 1 1 " at an angle θ of approximately 20° with respect to the horizontal and which are fixed to one another along a respective apex 9, 10. The height h. of the apex 9, 10 above the lattice girder 4 is, for example, 1.45 m. In the longitudinal direction L the pairs of roof surfaces 5, 6; 7, 8 are provided with transverse ribs, formed by pairs of second roof surfaces 12, 13; 14, 15. The roof surfaces 12, 13; 14, 15 run at an angle γ from base edges 18. 19; 20, 21 and are joined to one another along edges at the apex 16, 17. The distance d : between the base edges 18, 19; 20, 21 of the pairs of second roof surfaces 12, 13; 14, 15 is, for example, 2 cm, whilst the height h 2 of the edge at the apex 16, 17 above the plane of the base edges 18, 19; 20, 21 is 1.7 cm. As a result of fitting the pairs of zigzag-shaped second roof surfaces 12, 13; 14, 15 the light yield is increased by approximately 10% for a single layer roof construction and by approximately 20% for a double layer roof construction as is shown in Figure 3 and Figure 4, compared with known greenhouses where only pairs of first roof surfaces 5, 6; 7, 8 are present. Figure 2 shows an embodiment of a greenhouse 28 having a roof construction 29 in which the base edges 30, 31, 32, 33 of pairs of first roof surfaces 34, 35 and pairs of second roof surfaces 36, 37 delimit rectangles in contact with one another, above which the roof surfaces 34, 35; 36, 37 come together in an apex 38, so that a multiplicity of pyramids 39, 40 is formed to increase the light yield. Here the length of the base edges 31, 32 is approximately 1 m, whilst the height of the pyramids is 1.7 m. Figure 3 shows an embodiment of a double-walled roof element 50 in the form of a hollow-core sheet having a base sheet 51 and pairs of roof surfaces 52, 53, 54, 55 which are joined to one another along edges at the apex 56, 57 extending peφendicularly to the plane of the drawing. The base edges 60, 61, 62, 63 are joined via partitions 58, 59 to the base sheet 1. The thickness b, of the base sheet is, for example, 0.8 mm, the thickness b 2 of the surfaces 52, 53, 54, 55 is, for example, 1 mm, the height h 3 is, for example, 28 mm, whilst the distance d 3 between the base edges 60, 61 , 62, 65 is, for example, 16 mm. The height h 5 is 13.9 mm. The angle θ of the roof surfaces 52, 53, 54. 55 to the horizontal is 60°. The material of the double-walled roof element 50 is, for example, polycarbonate, but this element can also be made from any other suitable transparent plastic. Figure 4 shows an alternative embodiment of a double-walled roof element 70 having roof surfaces 71, 72, which are positioned at an angle, and base surfaces 73, 74, which are likewise positioned at an angle and which are joined to one another by partitions 75, 76, 77. The thickness b 3 of the roof surfaces 71 , 72 is, for example, 1 mm, the distance h between the roof surfaces 71 , 72 and the base surfaces 73, 74 is, for example, 20 mm and the thickness b 4 of the partition 77 is, for example, 0.8 mm. The distance d 4 between the base edges 78, 79 is, for example, 30 mm. Figure 5 shows an embodiment of a roof element 80 made from one piece of transparent plastic and having a base sheet 81. Four surfaces 82, 83, 84, 85 extend along four base edges 86, 87, 88, 89 of the base sheet 81 to a common apex 90. In this way a multiplicity of pyramids uniformly distributed over the base sheet 81 are formed. Here the length of the base edges 86, 87, 88, 89 is, for example, 1.5 m and the distance from the apex 90 to the base sheet 81 is 2.6 m. Finally, Figure 6 shows two roof elements 90, 91 which are joined to one another via complementary fixing means 92, 93 which engage in a simple manner and in modular fashion form a roof construction according to the present invention.

Claims: Claims 1. Greenhouse (1 ,28) comprising a transparent roof construction (2,29) with a longitudinal direction (L) and a transverse direction (D) located peφendicularly thereto, having various pairs of first roof surfaces (5,6,7,8,36,37) in succession in the transverse direction (D), the first roof surfaces of a predetermined pair running at an angle (θ) with respect to a horizontal from a base edge (1 1,1 1', 1 1", 30, 33) oriented in the longitudinal direction (L) of the greenhouse to a common apex (9,10,38), characterised in that the greenhouse is provided with pairs of successive second roof surfaces (12,13,14, 15;34,35) in the longitudinal direction (L) , which second roof surfaces extend at an angle (γ) with respect to the horizontal from a base edge (18,19,20,21 ;31 ,32) oriented in the transverse direction (D) of the greenhouse to a common apex (16,17,38). 2. Greenhouse (28) according to Claim 1, characterised in that four mutually adjoining peφendicular base edges (30,31,32,33) each time delimit a rectangle, wherein the rectangles extend successively in the longitudinal direction (L) and the transverse direction (D) of the roof construction and wherein, for each rectangle, first and second pairs of roof surfaces (34,35,36,37) extend from the base edges (30,31,32,33) to a common apex (38) located above the rectangle concerned. 3. Greenhouse (1) according to Claim 1, characterised in that the pairs of first roof surfaces (5,6,7,8) are in contact with one another along edges at the apex (9,10), wherein the base edges (11, 11', 1 1 ") and the edges at the apex (9,10) of the pairs of first roof surfaces (5,6,7,8) extend parallel to one another in the longitudinal direction (L), wherein the pairs of second roof surfaces (12,13,14,15) are in contact with one another along edges at the apex (16,17) and wherein the base edges (18,19,20,21) and the edges at the apex (16,17) of the second pairs of roof surfaces (12,13,14,15) extend parallel to one another from a base edge (1 1, 11', 1 1") of a first roof surface (5,6,7,8) to the edge at the apex (9,10) of the first roof surface concerned. 4. Greenhouse (1,28) according to one of the preceding claims, characterised in that the roof surfaces (52,53,54,55) are of double-walled construction, having a base sheet (51,73,74) and transverse links (58,59,75,76,77) between the points of the apexes and/or the base edges (60,61,62,63,78,79) of the roof surfaces and the base sheet. 5. Greenhouse (1,28) according to Claim 3 or 4, characteπsed in that a distance (d 2 ,d 3 ,d 4 ) between the base edges (18,19,20,21,78,79) of the pairs of second roof surfaces (12,13,14,15,71,72) is between 0.5 and 0.001 times the distance (d,) between the base edges (1 1,1 l',l 1") of the pairs of first roof surfaces (5,6,7,8). 6. Greenhouse (1,28) according to Claim 3, 4 or 5, characteπsed in that a peφendicular distance (h,,h 5 ) between the edge at the apex (16,17,27,28) and the base edges (18,19,20,21,60,61,62,63) of the pairs of second roof surfaces is between 0.5 and 0.001 times the peφendicular distance between the edge at the apex (9,10) and the base edges (11,1 r,l 1") of the pairs of first roof surfaces (5,6,7,8). 7. Roof element (50,80) for use in a greenhouse, provided with various pairs of roof surfaces (52,53,54,55,82,83) in succession in a transverse direction (D) and a base sheet (51,81), wherein the roof surfaces of a predetermined pair run at an angle (θ) with respect to the base sheet from a base edge (60,61,62,63,86,88) oπented in a longitudinal direction (L) to a common apex (56,57,90), which roof surfaces (52,53,54, 55,82,83) are joined to the base sheet along the base edges and/or at the location of the apex. 8. Roof element (80) according to Claim 7, characteπsed in that the roof element is furthermore provided with pairs of second roof surfaces (84,85) in succession in a longitudinal direction (L) which run at an angle with respect to the base sheet (81) from a base edge (87,89) oπented in a transverse direction (D) to a common apex (90), wherein four base edges (86,87,88,89) peφendicular to one another always delimit a rectangle, wherein the rectangles extend successively in the longitudinal direction (L) and the transverse direction (D) of the base sheet (81) and wherein, for each rectangle, first and second pairs of roof surfaces (82,83,84,85) extend from the base edges (86,87,88,89) to a common apex (90) located above the rectangle concerned. 9. Roof element (50,80) according to Claim 7 or 8, characteπsed in that a distance between the base sheet (51 ,81) and the apex (56,57,90) is between 1 cm and 10 cm, preferably between 1 5 cm and 3 cm 10. Roof element (50,80) according to Claim 7, 8 or 9, characterised in that the distance (d 3 ,d 4 ) between the base edges is between 1 cm and 10 cm, preferably between 1.5 cm and 3 cm. 1 1. Roof element (50,80) according to Claim 7, 8 or 9, characterised in that the angle (θ) of the roof surfaces is between 30° and 75°, preferably between 45° and 75°. 12. Roof element (50,80) according to one of Claims 7 to 1 1, characterised in that the roof element consists of one piece and is made from transparent plastic having a wall thickness of between 0.5 mm and 5 mm, preferably between 0.5 mm and 2 mm. 13. Roof element (76,77) according to one of Claims 7 to 12, characterised in that the roof element is provided with coupling means (78,79) for joining to a similar roof element.

Inventors: SONNEVELD PIETER JAN, STOFFERS JOHANNES ANDREAS, SONNEVELD, PIETER, JAN, STOFFERS, JOHANNES, ANDREAS
Applicants: INST VOOR MILIEU EN AGRITECHNI, SONNEVELD PIETER JAN, STOFFERS JOHANNES ANDREAS, INSTITUUT VOOR MILIEU-EN AGRITECHNIEK (IMAG-DLO), SONNEVELD, PIETER, JAN, STOFFERS, JOHANNES, ANDREAS
Application year: 2000
Main classification: A01G9
IPC codes: A01G9