Ventilation sheet for agricultural greenhouses

Abstract

To provide ventilation sheets that can maintain the effect of suppressing the occurrence of blocking for a long time.SOLUTION: A ventilation sheet 10 is used in an agricultural greenhouse with a plurality of frame members, is arranged so as to allow wind-up and wind-down motions along a portion of the plurality of framework members and has a pair of surfaces. On one of the pair of surfaces, a large number of projections 14 having a hemispherical shape are formed.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a ventilation sheet for use in an agricultural greenhouse. [Background technology]

[0002] Conventionally, agricultural greenhouses for controlling temperature according to crops have been known. The agricultural greenhouses include a framework including a plurality of framework members and a covering material including a plurality of agricultural sheets arranged to cover the framework and supported by the framework. Some conventional agricultural greenhouses are also known to be capable of ventilating the greenhouse by rolling up some of the agricultural sheets (for example, Patent Document 1).

[0003] However, when the ventilation sheet is rolled up and down, blocking, a phenomenon in which overlapping portions of the ventilation sheet stick together, is likely to occur. When such blocking occurs, there is a problem that the ventilation sheet cannot be rolled up and down smoothly. One possible measure to prevent such blocking from occurring is to apply an anti-blocking agent, such as a powder mainly composed of starch, to the surface of the ventilation sheet.

[0004] However, anti-blocking agents increase the haze of the ventilation sheet, which reduces the light transmittance of the ventilation sheet, and also cause a deterioration in the working environment, such as by staining the hands of workers who apply the anti-blocking agent. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-317088 Summary of the Invention [Problem to be solved by the invention]

[0006] One possible measure to suppress blocking without using a blocking inhibitor is to form a large number of protrusions on the surface of the ventilation sheet. However, even in this case, the protrusions must be durable against the load (friction load) caused by friction that occurs when the ventilation sheet is rolled up and down. Specifically, when the ventilation sheet is rolled up and down, friction loads such as friction between the ventilation sheet and the framework material and friction between overlapping portions of the ventilation sheet act on the protrusions of the ventilation sheet. Therefore, in order to maintain the effect of suppressing blocking over the long term, the protrusions must be durable against such friction loads. [Means for solving the problem]

[0007] The present invention has been made in light of the above-mentioned problems, and aims to provide a ventilation sheet that can maintain the effect of suppressing the occurrence of blocking for a long period of time.

[0008] The ventilation sheet of the present invention is used in an agricultural greenhouse having a plurality of frame members, is arranged along a portion of the frame members so as to be capable of being rolled up and down, and has a pair of surfaces, one of which has a number of hemispherical protrusions formed thereon.

[0009] In this ventilation sheet, a large number of protrusions are formed on the one surface, which can suppress the occurrence of blocking when the ventilation sheet is rolled up and down, and the large number of protrusions have a hemispherical shape, which makes them durable against the friction load that occurs when the ventilation sheet is rolled up and down, thereby making it possible to maintain the effect of suppressing the occurrence of blocking for a long period of time.

[0010] The multiple frame members include multiple roof support members arranged in a portion corresponding to the roof of the agricultural greenhouse. The agricultural greenhouse has a top sheet arranged on the multiple roof support members and supported by the multiple roof support members, and side sheets forming the sides of the agricultural greenhouse. The ventilation sheet is arranged on the multiple roof support members between the top sheet and the side sheets and supported by the multiple roof support members, and is configured to be able to be rolled up and down along the multiple roof support members. Preferably, the one surface on which the multiple protrusions are formed is the underside facing the multiple roof support members. In this configuration, because the ventilation sheet is arranged on and supported by the multiple roof support members, the weight of the ventilation sheet acts on the multiple roof support members. This makes it easy for the rubbing load on the underside of the ventilation sheet to increase during roll-up and roll-down operations. Even in such cases, the multiple hemispherical protrusions formed on the underside are durable against the rubbing load, thereby maintaining the effect of suppressing blocking over a long period of time.

[0011] It is more preferable that the other of the pair of surfaces, the upper surface, has an uneven shape to diffuse light entering the agricultural greenhouse. In this configuration, the uneven shape of the upper surface of the ventilation sheet can diffuse light such as sunlight, allowing light entering the agricultural greenhouse to reach a wider area within the greenhouse and reducing the likelihood of shadows. Furthermore, since the upper surface of the ventilation sheet is located opposite the lower surface that contacts the roof support members, this upper surface is not subjected to friction loads from the roof support members, and the uneven shape does not wear out due to contact with the roof support members. In other words, in this configuration, by forming multiple protrusions on the underside of the ventilation sheet that are durable against the friction load, the effect of suppressing blocking can be maintained for a long period of time, while by forming the uneven shape on the upper surface of the ventilation sheet, the effect of directing light entering the agricultural greenhouse to a wider area within the agricultural greenhouse can be maintained for a long period of time.

[0012] The ventilation sheet may be positioned to form at least a portion of the side of the agricultural greenhouse, the one surface on which the numerous protrusions are formed being the inner surface of the ventilation sheet, the multiple frame members including at least one frame member positioned adjacent to the inner surface of the ventilation sheet and extending along the inner surface, and the ventilation sheet may be configured to be able to be rolled up and down along the at least one frame member. When the ventilation sheet is positioned to form at least a portion of the side of the agricultural greenhouse and rolled up and down along the at least one frame member, the friction load acts on the inner surface of the ventilation sheet during the roll-up and roll-down operations. Even in such a case, the numerous hemispherical protrusions formed on the inner surface are durable against the friction load, so that the effect of suppressing blocking is maintained for a long period of time.

[0013] It is more preferable that the other of the pair of surfaces, the outer surface, has an uneven shape to diffuse light entering the agricultural greenhouse. In this configuration, the uneven shape of the outer surface of the ventilation sheet can diffuse light such as sunlight, making it easier for light entering the agricultural greenhouse to reach a wider area within the agricultural greenhouse and reducing the likelihood of shadows. Furthermore, since the outer surface of the ventilation sheet is located opposite the inner surface that contacts the frame material, this outer surface is not subjected to rubbing loads from the frame material, and the uneven shape does not wear due to contact with the frame material. In other words, in this configuration, by forming multiple protrusions that are durable against the rubbing load on the inner surface of the ventilation sheet, the effect of suppressing blocking can be maintained for a long time, while by forming the uneven shape on the outer surface of the ventilation sheet, the effect of directing light entering the agricultural greenhouse to a wider area within the agricultural greenhouse can be maintained for a long time.

[0014] The outer diameter of each of the numerous protrusions is preferably within a range of 70 μm to 900 μm. With this configuration, it is possible to more effectively suppress the occurrence of blocking and more effectively increase the durability of the protrusions against the rubbing load.

[0015] 4mm in the ventilation sheet 2 The number of the protrusions per contact point is preferably a value within a range of 5 to 170. In this configuration, the occurrence of blocking can be more effectively suppressed, and the durability of the protrusions against the rubbing load can be more effectively increased.

[0016] In the ventilation sheet, the other of the pair of surfaces may have a large number of hemispherical projections formed thereon. [Effects of the Invention]

[0017] According to the present invention, a ventilation sheet is provided that can maintain for a long period of time the effect of suppressing the occurrence of blocking when the ventilation sheet for an agricultural greenhouse is rolled up and down. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a perspective view showing an agricultural greenhouse in which a ventilation sheet according to an embodiment of the present invention is used. [Figure 2] FIG. 2 is a perspective view showing a roof portion of the agricultural greenhouse. [Figure 3] 10A and 10B are diagrams illustrating the operation of rolling up the ventilation sheet. [Figure 4] 3 is a photograph showing an enlarged view of a portion of the surface of the ventilation sheet according to the embodiment. [Figure 5] FIG. 2 is a plan view schematically illustrating a portion of the surface of the ventilation sheet according to the embodiment. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. [Figure 7] 10A and 10B are diagrams illustrating another example of the operation of rolling up the ventilation sheet. [Figure 8]FIG. 10 is a side view of a portion of the ventilation sheet according to the first modified example of the embodiment. [Figure 9] FIG. 10 is a cross-sectional view showing a part of a ventilation sheet according to a second modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] A preferred embodiment of the present invention will now be described with reference to the drawings.

[0020] Fig. 1 is a perspective view showing a row of agricultural greenhouses 100, 100, and Fig. 2 is a perspective view showing the roof portions of the agricultural greenhouses 100, 100. In this embodiment, two agricultural greenhouses 100, 100 each extending in a front-to-rear direction D1 are arranged adjacent to each other in a left-to-right direction D2. Each of these agricultural greenhouses 100, 100 is a so-called vinyl greenhouse, and includes, for example, a framework including a plurality of framework members, and a covering material including a plurality of agricultural sheets arranged to cover the framework and supported by the framework.

[0021] The multiple frame members include multiple pillar members 101, multiple beam members 102, and multiple roof support members 103. Each of the multiple pillar members 101 is arranged in a vertically extending position. The multiple pillar members 101 include at least four pillar members 101 arranged at the four corners of the agricultural greenhouse 100. The multiple pillar members 101 may further include at least one pillar member 101 arranged between two of the four pillar members 101. Each of the multiple beam members 102 is arranged in a horizontally extending position so as to span the upper ends of adjacent pillar members 101. The multiple roof support members 103 are arranged in a portion corresponding to the roof of the agricultural greenhouse 100 and are arranged at intervals from each other in the front-to-rear direction D1. Each of the multiple roof support members 103 is arranged so as to span two beam members 102, 102 arranged at an interval from each other in the left-to-right direction D2. Each of the plurality of roof support members 103 has, for example, an upwardly curved bow shape.

[0022] The multiple agricultural sheets include a front side sheet 107 that forms the front side of the agricultural house 100, an unillustrated rear side sheet that is arranged at a distance from the front side sheet 107 in the front-to-rear direction D1 and forms the rear side of the agricultural house 100, a left side sheet 108L and a right side sheet 108R that form the left and right sides of the agricultural house 100, respectively, a top sheet 106 that forms the top surface of the agricultural house 100, and multiple ventilation sheets 10.

[0023] The top sheet 106 is placed on top of and supported by the multiple roof support members 103. The top sheet 106 is attached to the multiple roof support members 103 with a gap between the right edge of the top sheet 106 and the upper edge of the right side sheet 108R, and with a gap between the left edge of the top sheet 106 and the upper edge of the left side sheet 108L. As a result, a right ventilation opening 109R is formed between the top sheet 106 and the right side sheet 108R, and a left ventilation opening 109L is formed between the top sheet 106 and the left side sheet 108L.

[0024] As shown in Fig. 2, a valley 110, which is an elongated portion extending in the front-to-rear direction D1 and recessed downward, is formed between two agricultural greenhouses 100, 100 adjacent to each other on the left and right. A gutter 111 extending in the front-to-rear direction D1 is arranged in this valley 110. The gutter 111 is arranged between the left ventilation opening 109L of the right agricultural greenhouse 100 and the right ventilation opening 109R of the left agricultural greenhouse 100.

[0025] 1 and 2, in each agricultural greenhouse 100, the multiple ventilation sheets 10 include a left ventilation sheet 10 arranged at a position corresponding to the left ventilation opening 109L, and a right ventilation sheet 10 arranged at a position corresponding to the right ventilation opening 109R. The left ventilation sheet 10 has a band shape extending in the front-to-rear direction D1 and is large enough to cover the left ventilation opening 109L. The right ventilation sheet 10 has a band shape extending in the front-to-rear direction D1 and is large enough to cover the right ventilation opening 109R.

[0026] The left ventilation sheet 10 has an upper edge that extends along the left edge of the top sheet 106, and a lower edge on the opposite side. The upper edge of the left ventilation sheet 10 or a portion nearby is fixed to the left edge of the top sheet 106 and / or to the multiple roof support members 103. A winding pipe 104, which is a rod-shaped member used to roll up and roll down the ventilation sheet 10, is fixed to the lower edge of the left ventilation sheet 10 or a portion nearby. The winding pipe 104 has a shape that extends linearly in the front-to-rear direction D1 along the lower edge of the left ventilation sheet 10. A winding motor 105, which is a motor that can rotate the winding pipe 104 around its axis, is attached to one end of the winding pipe 104.

[0027] Similarly, the right ventilation sheet 10 has an upper edge that extends along the right edge of the top sheet 106 and a lower edge on the opposite side. The upper edge of the right ventilation sheet 10 or a portion nearby is fixed to the right edge of the top sheet 106 and / or to the multiple roof support members 103. A winding pipe 104, which is a rod-shaped member used to roll up and roll down the ventilation sheet 10, is fixed to the lower edge of the right ventilation sheet 10 or a portion nearby. The winding pipe 104 has a shape that extends linearly in the front-to-rear direction D1 along the lower edge of the right ventilation sheet 10. A winding motor 105, which is a motor capable of rotating the winding pipe 104 around its axis, is attached to one end of the winding pipe 104.

[0028] FIG. 3 is a diagram illustrating the operation of rolling up the ventilation sheet 10. When the winding motor 105 rotates in one direction, the winding pipe 104 rotates around its axis in the same direction as the winding motor 105 as shown in FIG. 3, and moves upward along the multiple roof support members 103 while winding the ventilation sheet 10 around the winding pipe 104 in order from the bottom side. As a result, the ventilation sheet 10 is rolled up upward by the winding pipe 104. As the winding amount, which is the amount of ventilation sheet 10 wound up by the winding pipe 104, increases, the open area of ​​the ventilation opening (109L or 109R) becomes larger as shown in FIG. 2. This open area is the part of the ventilation opening that is not blocked by the ventilation sheet 10, and is an area where ventilation of the agricultural greenhouse 100 can be performed.

[0029] When the winding motor 105 rotates in the opposite direction to the one direction, the winding pipe 104 rotates around its axis in the same direction as the winding motor 105, and moves downward along the multiple roof support members 103 while unwinding the ventilation sheet 10 from the winding pipe 104. As a result, the ventilation sheet 10 is wound down by the winding pipe 104. As the amount of winding decreases, the open area becomes smaller. When the ventilation sheet 10 is wound down to the lowest limit, it can completely block the ventilation opening (109L or 109R).

[0030] As shown in Fig. 2, the ventilation sheet 10 on the right side of the agricultural greenhouse 100 on the left side and the ventilation sheet 10 on the left side of the agricultural greenhouse 100 on the right side are arranged in the valley portions 110 of the row-type agricultural greenhouses 100, 100. These ventilation sheets 10, 10 are sheets for so-called valley ventilation (valley ventilation sheets) that ventilate the agricultural greenhouses 100, 100 in the valley portions 110.

[0031] As shown in FIG. 2, each of the left and right agricultural greenhouses 100, 100 further includes a plurality of holding bands 112, which are holding members for holding down the left ventilation sheet 10 from above, and a plurality of holding bands 112, which are holding members for holding down the right ventilation sheet 10 from above. Each of the plurality of holding bands 112 is a member arranged to stabilize the rolling up and rolling down of the corresponding ventilation sheet 10 of the left and right ventilation sheets 10, 10. Each of the plurality of holding bands 112 has an upper end fixed near the upper edge of the ventilation sheet 10 and a lower end fixed near the lower edge of the ventilation opening (109L or 109R), and is a member arranged on the ventilation sheet 10 and extending from the upper end to the lower end along the upper surface of the ventilation sheet 10. Therefore, each ventilation sheet 10 is arranged so as to be sandwiched between the plurality of roof support members 103 and the plurality of holding bands 112.

[0032] Each of the left and right ventilation sheets 10, 10 is a transparent sheet made of synthetic resin. Examples of the synthetic resin include, but are not limited to, ethylene vinyl acetate (EVA) and polyethylene (PE). Of the multiple agricultural sheets, sheets other than the left and right ventilation sheets 10, 10, such as the top sheet 106, the front side sheet 107, the rear side sheet, the left side sheet 108L, and the right side sheet 108R, may be made of the same synthetic resin as the ventilation sheet 10, or may be made of a different synthetic resin from the ventilation sheet 10.

[0033] As described above, each ventilation sheet 10 is sandwiched between the plurality of roof support members 103 and the plurality of press bands 112, and is rolled up by the rolling pipe 104 and rolled down by the rolling pipe 104. Therefore, the rolling up and rolling down of the ventilation sheet 10 is performed while the ventilation sheet 10 rubs against the plurality of roof support members 103 and the plurality of press bands 112. Furthermore, the rolling up and rolling down of the ventilation sheet 10 is performed while overlapping portions of the ventilation sheet 10 rub against each other as the ventilation sheet 10 is rolled up around the rolling pipe 104.

[0034] If the surface of the ventilation sheet made of the above-mentioned synthetic resin is smooth, blocking is likely to occur when the ventilation sheet is rolled up and down, in which overlapping parts stick together as the sheet is wound around the winding pipe 104. When such blocking occurs, there is a problem that the ventilation sheet cannot be rolled up and down smoothly.

[0035] One possible measure to prevent the occurrence of blocking as described above is to apply an anti-blocking agent, such as a powder mainly composed of starch, to the surface of the ventilation sheet. However, the anti-blocking agent increases the haze of the ventilation sheet, which reduces the light transmittance of the ventilation sheet. It also causes the hands of workers who apply the anti-blocking agent to become dirty, which deteriorates the working environment.

[0036] One possible solution to suppress blocking without using a blocking inhibitor is to form multiple protrusions on the surface of the ventilation sheet. However, even in this case, the protrusions must be durable against friction that occurs when the ventilation sheet is rolled up and down. Specifically, friction loads, which are loads on the surface of the ventilation sheet, such as friction between the ventilation sheet and multiple roof support members 103, friction between the ventilation sheet and multiple retaining bands 112, and friction between overlapping portions of the ventilation sheet 10, occur each time the ventilation sheet is rolled up and down. If such friction loads repeatedly act on the protrusions on the surface of the ventilation sheet, the protrusions formed on the ventilation sheet will gradually become smooth, and the effect of suppressing blocking will not be fully achieved. Therefore, to maintain the effect of suppressing blocking over the long term, the protrusions must be durable against such friction loads.

[0037] Each of the ventilation sheets 10, 10 according to this embodiment has the following configuration in order to suppress blocking and to achieve durability of the convex portions against the rubbing load.

[0038] Fig. 4 is a photograph of an enlarged portion of the surface 11 of the ventilation sheet 10 according to this embodiment. Fig. 5 is a diagram schematically illustrating a portion of the surface 11 of the ventilation sheet 10, and Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 5. Since the left and right ventilation sheets 10, 10 have the same structure, the following description will mainly focus on one of the left and right ventilation sheets 10, 10.

[0039] As shown in Figs. 4 to 6, the ventilation sheet 10 according to this embodiment includes a base portion 13 and a large number of protrusions 14. The base portion 13 is a film-like portion that extends across the entire area of ​​the ventilation sheet 10 in a plan view. Each of the large number of protrusions 14 is a protruding portion that protrudes from the base portion 13 in the thickness direction of the ventilation sheet 10. In other words, the ventilation sheet 10 has a pair of surfaces including one surface 11 and an opposite surface 12 (rear surface 12), and has a large number of protrusions 14 formed on one surface 11.

[0040] Each of the numerous protrusions 14 has a hemispherical shape. Forming numerous hemispherical protrusions 14 on the surface 11 in this manner makes it possible to control the contact area between the surface 11 and an object that comes into contact with the surface 11. This makes it possible to suppress the occurrence of blocking without using a blocking inhibitor, thereby avoiding the reduction in light transmittance of the ventilation sheet 10 and the deterioration of the working environment that would be caused by a blocking inhibitor.

[0041] Furthermore, forming a large number of hemispherical protrusions 14 on the surface 11 makes it easier to evenly distribute the contact portions of the large number of protrusions 14 across one surface 11 of the ventilation sheet 10 while minimizing the area of ​​the contact portion where each protrusion 14 comes into contact with the contact object, compared to when the protrusions have a shape other than hemispherical, such as when strip-like protrusions are arranged on the surface or when a large number of rectangular protrusions are formed on the surface. This makes it easier to increase the slipperiness between the surface 11 and the contact object across the entire ventilation sheet 10, compared to when the protrusions have a shape other than hemispherical, thereby increasing the durability of the protrusions 14 against the rubbing load. As a result, the effect of suppressing the occurrence of blocking can be maintained for a long period of time.

[0042] In this embodiment, each of the ventilation sheets 10 is placed on a plurality of roof support members 103, is supported by the plurality of roof support members 103, and is configured so as to be able to perform a rolling up and rolling down operation along the plurality of roof support members 103. Therefore, one surface 11 on which the plurality of protrusions 14 are formed is the underside 11 facing the plurality of roof support members 103, as shown in Figure 3. That is, in this embodiment, the ventilation sheet 10 is placed so that one surface 11 on which the plurality of protrusions 14 are formed faces downward.

[0043] Here, the term "hemispherical shape" does not only refer to the shape of a hemisphere obtained by dividing a sphere into two equal parts, but also includes shapes similar to a hemisphere. Specifically, the term "hemispherical shape" refers not only to cases where the shape of the protrusions 14 is circular when the ventilation sheet 10 is viewed in plan, but also to cases where the shape of the protrusions is oval, such as egg-shaped, oval, or elliptical, and to cases where the shape of the protrusions is intermediate between a circle and an oval. Furthermore, the term "hemispherical shape" refers not only to cases where the protrusion height of the protrusions 14 from the base portion 13 is the same as the radius of the protrusions 14 when viewed in plan, but also to cases where the protrusion height of the protrusions 14 is greater than or less than the radius of the protrusions 14 when viewed in plan.

[0044] The ventilation sheet 10 according to this embodiment can be produced by, for example, the manufacturing method described below. In this case, the "semispherical shape" also includes shapes with variations that may occur when forming a large number of protrusions 14 by that manufacturing method. Specifically, when the ventilation sheet 10 is produced by, for example, the manufacturing method described below, most of the multiple protrusions 14 have a shape like the smaller of two parts obtained by cutting a sphere on a plane, protruding from the base portion 13. Therefore, when the ventilation sheet 10 is produced by, for example, the manufacturing method described below, the "semispherical shape" can be said to be a shape that includes the shape of a hemisphere obtained by bisecting a sphere and the shape like the smaller of two parts obtained by cutting a sphere on a plane, protruding from the base portion 13.

[0045] The ventilation sheet 10 according to this embodiment can be manufactured using, for example, the following manufacturing method. That is, by passing a synthetic resin material, which is the material that constitutes the ventilation sheet 10, between a pair of rolls (not shown), it is possible to manufacture a ventilation sheet 10 having a large number of protrusions 14 formed on one surface 11. Of the pair of rolls, a large number of recesses are formed in advance on the surface of the roll that corresponds to the surface 11 on which the large number of protrusions 14 are formed. The pair of rolls may be adjusted to a predetermined temperature, and the synthetic resin material may be a sheet-like material or a molten material.

[0046] The numerous recesses on the surface of the roll are formed, for example, by blasting the surface of the roll. The blasting material used in the blasting is selected according to the target size of the numerous protrusions 14 to be formed on the surface 11 of the ventilation sheet 10. The blasting time is determined according to the target density (e.g., the target number per unit area) of the numerous protrusions 14 to be formed on the surface 11 of the ventilation sheet 10. As the blasting material, for example, spherical beads are used. Examples of spherical beads include steel beads and stainless steel beads. For example, when numerous protrusions are to be formed on both one surface 11 and the other surface 12 of the ventilation sheet 10 as shown in Figure 9 described below, numerous recesses are formed in advance on the surface of each of the pair of rolls in the same manner as above. However, the manufacturing method for producing the ventilation sheet 10 is not limited to the above method and other methods may be used.

[0047] In addition, in this embodiment, in order to more effectively suppress the occurrence of blocking and more effectively increase the durability of the convex portions 14 against the rubbing load, the ventilation sheet 10 has a large number of convex portions 14 each having an outer diameter within a specific outer diameter range, and the large number of convex portions 14 are arranged at a density within a specific density range.

[0048] When the shape of the convex portions 14 when the ventilation sheet 10 is viewed in a plane as in Figures 4 and 5, for example, is a circle, the outer diameter of the convex portions 14 is the diameter of the convex portions 14 in the plane view. When the shape of the convex portions 14 when the ventilation sheet 10 is viewed in a plane is an oval shape, for example an ellipse, the outer diameter of the convex portions 14 is the average value of the length of the major axis (major diameter) of the convex portions 14 and the length of the minor axis (minor diameter) of the convex portions 14 in the plane view. Furthermore, when the shape of the convex portions 14 when the ventilation sheet 10 is viewed in a plane is, for example, an intermediate shape between a circle and an oval, the outer diameter of the convex portions 14 is the average value of the longest length of the convex portions 14 when viewed in a plane and the length in the direction perpendicular to that.

[0049] If the outer diameter of the protrusions 14 in the ventilation sheet 10 becomes too small, the height of the protrusions 14 also becomes small accordingly, and so the time it takes for the protrusions 14 to be worn down and become smooth when the rubbing load is repeatedly applied tends to be short. Also, if the outer diameter of the protrusions 14 in the ventilation sheet 10 becomes too small, the height of the protrusions 14 also becomes small accordingly, and so it may not be possible to sufficiently reduce the area (contact area) where the overlapping parts stick together when wound around the winding pipe 104, and as a result, the effect of suppressing the occurrence of blocking may not necessarily be fully achieved.

[0050] If the outer diameter of the convex portion 14 in the ventilation sheet 10 becomes too large, the contact area between the convex portion 14 and the contact object (other parts of the ventilation sheet 10) that comes into contact with it when the sheet is wound around the winding pipe 104 will become large, and the effect of suppressing the occurrence of blocking may not necessarily be fully achieved.

[0051] If the density of the numerous protrusions 14 in the ventilation sheet 10 becomes too small, the spacing between the protrusions 14 becomes large, and the proportion of the area of ​​the peripheral portion of the surface 11 of the ventilation sheet 10 other than the protrusions 14 increases. This increases the contact area between the surface 11 of the ventilation sheet 10 and the contact object that rubs against this surface 11 (for example, the presser band 112, the roof support member 103, etc.) when the ventilation sheet 10 is rolled up and down. If the contact area becomes large, the slipperiness between the surface 11 of the ventilation sheet 10 and the contact object decreases when the ventilation sheet 10 is rolled up and down, increasing the friction between them. As a result, it may not be possible to sufficiently increase the durability of the protrusions against the rubbing load. Furthermore, if the density of the numerous protrusions 14 in the ventilation sheet 10 becomes too low, the proportion of the area of ​​the peripheral part of the surface 11 of the ventilation sheet 10 other than the protrusions 14 increases, so when the ventilation sheet 10 is wound around the winding pipe 104 and parts of the ventilation sheet 10 overlap, not only the protrusions 14 but also the peripheral part are likely to stick to other parts of the ventilation sheet 10. For this reason, the effect of suppressing the occurrence of blocking may not necessarily be fully achieved.

[0052] If the density of the numerous protrusions 14 in the ventilation sheet 10 becomes too high, the number of protrusions 14 that come into contact with contact objects such as the holding bands 112 and roof support members 103 will also increase, which may reduce the slipperiness between the surface 11 of the ventilation sheet 10 and the contact objects when rolling up and down. This increases friction between them, and as a result, it may not be possible to sufficiently increase the durability of the protrusions against the rubbing load.

[0053] The specific outer diameter range and the specific density range are set in advance based on the above-mentioned viewpoints. For example, a plurality of ventilation sheets 10 are produced with different outer diameter ranges and different density ranges, and the blocking suppression effect and the durability of the protrusions 14 against the rubbing load are evaluated for each of them. In this way, the specific outer diameter range and the specific density range can be set.

[0054] The preferred specific outer diameter range and specific density range set based on the above viewpoints are as follows. Note that, hereinafter, the range of the number of protrusions 14 per unit area of ​​the ventilation sheet 10 is used as the specific density range. The outer diameter of each of the numerous protrusions 14 in the ventilation sheet 10 is preferably a value within the range of 70 μm to 900 μm, and the number of protrusions 14 per unit area of ​​the ventilation sheet 10 is preferably 4 mm. 2 The number of contact protrusions 14 is preferably within a range of 5 to 170. This more effectively suppresses the occurrence of blocking and more effectively increases the durability of protrusions 14 against the rubbing load.

[0055] Note that when a large number of protrusions 14 on the surface 11 of the ventilation sheet 10 are formed by, for example, the manufacturing method described above, it may be difficult to control the outer diameters of all of the protrusions 14 completely within the above-mentioned specific outer diameter range. Therefore, in the ventilation sheet 10 according to this embodiment, it is preferable that 80% or more of all of the protrusions 14 on the surface 11 have a value within the range of 70 μm to 900 μm, and it is even more preferable that 90% or more of all of the protrusions 14 on the surface 11 have a value within the range of 70 μm to 900 μm.

[0056] More specifically, when the synthetic resin constituting the ventilation sheet 10 is polyethylene (PE), the specific outer diameter range and specific density range are preferably as follows: The outer diameter of each of the numerous protrusions 14 in the ventilation sheet 10 is preferably a value within the range of 75 μm to 650 μm, and more preferably a value within the range of 80 μm to 340 μm.

[0057] When the synthetic resin constituting the ventilation sheet 10 is ethylene vinyl acetate (EVA), the specific outer diameter range and specific density range are preferably as follows: The outer diameter of each of the numerous protrusions 14 in the ventilation sheet 10 is preferably a value within the range of 70 μm to 900 μm, and more preferably a value within the range of 160 μm to 330 μm.

[0058] Table 1 summarizes the specific outer diameter ranges and specific density ranges of multiple ventilation sheets 10 fabricated with different outer diameter ranges and density ranges to evaluate the blocking prevention effect and the durability of the protrusions 14 against the rubbing load. Of the six ventilation sheets 10 in Table 1, EVA(1), EVA(2), and EVA(3) are made of EVA as the synthetic resin, while PE(1), PE(2), and PE(3) are made of polyethylene as the synthetic resin. All six ventilation sheets 10 achieved blocking prevention and durability of the protrusions 14 against the rubbing load. Of these six ventilation sheets 10, EVA(2) and PE(2) were well-balanced in terms of blocking prevention effect and durability of the protrusions 14 against the rubbing load. The outer diameter (particle size) of each of the numerous protrusions 14 in the ventilation sheet 10 made of EVA(2) was within the range of 160μm to 330μm. The outer diameter (particle size) of each of the numerous protrusions 14 in the ventilation sheet 10 made of PE(2) was within the range of 80μm to 340μm. Of the six ventilation sheets 10, the outer diameter (particle size) of each of the numerous protrusions 14 in the ventilation sheets 10 made of EVA(1) and EVA(3) was within the range of 70μm to 900μm, and the outer diameter (particle size) of each of the numerous protrusions 14 in the ventilation sheets 10 made of PE(1) and PE(3) was within the range of 75μm to 650μm.

[0059] [Table 1]

[0060] Next, the results of the following slipperiness test and abrasion resistance test conducted on the six ventilation sheets 10 in Table 1 will be described.

[0061] The surface 11 (one surface on which numerous protrusions 14 were formed) of each of EVA (1), EVA (2), and EVA (3) was brought into surface contact with the surface (smooth surface) of another EVA sheet, and the slipperiness (ease of slipping) of the surface 11 of each of EVA (1), EVA (2), and EVA (3) relative to the smooth surface was evaluated. Note that the smooth surface is a surface on which no irregularities were formed. As a result, the slipperiness of EVA (1) and EVA (2) was better than that of EVA (3).

[0062] In addition, the abrasion resistance of the surfaces 11 of EVA (1) and EVA (2) was evaluated by bringing the surfaces 11 of EVA (1) and EVA (2) into surface contact with the smooth surface of another EVA sheet and moving one sheet back and forth relative to the other sheet multiple times. As a result, the abrasion resistance of EVA (1) and the abrasion resistance of EVA (2) were found to be equivalent. As for EVA (3), the slipperiness of EVA (3) was lower than that of EVA (1) and EVA (2), so it was not included in the evaluation of abrasion resistance.

[0063] The surface 11 (one surface on which numerous protrusions 14 were formed) of each of PE(1), PE(2), and PE(3) was brought into surface contact with the surface (smooth surface) of another PE sheet, and the slipperiness (ease of sliding) of the surface 11 of each of PE(1), PE(2), and PE(3) relative to the smooth surface was evaluated. As a result, the slipperiness of PE(1) and PE(2) was better than that of PE(3).

[0064] In addition, the surface 11 of each of PE (1) and PE (2) was brought into surface contact with the smooth surface of the other PE sheet, and one sheet was moved back and forth relative to the other sheet multiple times to evaluate the abrasion resistance of the surface 11 of each of PE (1) and PE (2). As a result, the abrasion resistance of PE (2) was better than that of PE (1). As for PE (3), the slipperiness of PE (3) was lower than that of PE (1) and PE (2), so it was not included in the evaluation of abrasion resistance.

[0065] Furthermore, the slipperiness of PE(1) and PE(2) was better than that of EVA(1) and EVA(2). The abrasion resistance of PE(1) and PE(2) was better than that of EVA(1) and EVA(2). Of the six ventilation sheets 10 in Table 1, PE(2) was the best in terms of the slipperiness test and abrasion resistance test.

[0066] Next, the abrasion resistance of the ventilation sheet 10 made of PE(2) was compared with the abrasion resistance of Comparative Examples 1 and 2 described below. In this abrasion resistance test, the same ventilation sheet 10 made of PE(2) as shown in PE(2) in Table 1 was used. Furthermore, the sheet used in Comparative Example 1 was made of polyethylene synthetic resin, had smooth surfaces on both sides, and had powder (anti-blocking agent) applied to both sides. The sheet used in Comparative Example 2 was made of polyethylene synthetic resin, had smooth surfaces on both sides, and had powder (anti-blocking agent) applied to both sides.

[0067] The test method for this abrasion resistance test is as follows. The abrasion resistance of the surface 11 of the ventilation sheet 10 of PE (2) (one surface on which numerous convex portions 14 are formed) was evaluated by bringing the surface 11 (one surface on which a large number of convex portions 14 is formed) of the ventilation sheet 10 of PE (2) into surface contact with the surface of a PE sheet on which a matte surface shape (uneven shape) was formed, and then moving one sheet back and forth multiple times against the other sheet. Similarly, the abrasion resistance of the surface of the sheet of Comparative Example 1 was evaluated by bringing the surface (smooth surface) of the sheet of Comparative Example 1 into surface contact with the surface of a sheet on which a matte surface shape (uneven shape) was formed, and then moving one sheet back and forth multiple times against the other sheet. Furthermore, the abrasion resistance of the surface of the sheet of Comparative Example 2 was evaluated by bringing the surface (smooth surface) of the sheet of Comparative Example 2 into surface contact with the surface of a sheet on which a matte surface shape (uneven shape) was formed, and then moving one sheet back and forth multiple times against the other sheet.

[0068] The abrasion resistance of the surface 11 of the ventilation sheet 10 of PE(2) was evaluated by contacting the surface 11 of the ventilation sheet 10 with the surface of a pipe and moving the pipe back and forth multiple times against the surface 11. Similarly, the abrasion resistance of the smooth surface of the sheet of Comparative Example 1 was evaluated by contacting the surface (smooth surface) of the sheet of Comparative Example 1 with the surface of a pipe and moving the pipe back and forth multiple times against the smooth surface. The abrasion resistance of the smooth surface of the sheet of Comparative Example 2 was also evaluated by contacting the surface (smooth surface) of the sheet of Comparative Example 2 with the surface of a pipe and moving the pipe back and forth multiple times against the smooth surface. These test results are shown in Table 2.

[0069] As shown in Table 2, the ventilation sheet 10 of PE(2) had a higher number of reciprocating movements (number of times) until the sheet broke than Comparative Example 1 and Comparative Example 2, regardless of whether the contact object was the mat-like surface of the sheet or the surface of a pipe, and was therefore more abrasion-resistant.

[0070] [Table 2]

[0071] As described above, PE(2) was the best in terms of the sliding property test and the abrasion resistance test, and the outer diameter (particle size) of each of the numerous convex portions 14 in the ventilation sheet 10 of PE(2) was within the range of 80 μm to 340 μm. In this ventilation sheet 10 of PE(2), by forming numerous convex portions 14 in the above-mentioned outer diameter range on one surface 11 and forming a mat-like surface shape (uneven shape) on the other surface 12, the following effects are thought to be obtained. That is, when the ventilation sheet 10 of PE(2) is actually used as a ventilation sheet for an agricultural greenhouse, wear of the sheet when the sheet is rolled up and down is effectively suppressed, extending the usable life of the sheet. Furthermore, workability is improved when installing the ventilation sheet 10 of PE(2) on the framework of the agricultural greenhouse (workability is improved when unrolling the sheet). Furthermore, the load on the motor that rolls up and down the ventilation sheet 10 of PE(2) can be reduced.

[0072] FIG. 7 is a diagram illustrating another example of the operation of rolling up the ventilation sheet 10. As shown in FIG. 7, the ventilation sheet 10 may be positioned so as to form at least a portion of the left side of the agricultural greenhouse 100, so as to form at least a portion of the right side of the agricultural greenhouse 100, so as to form at least a portion of the front side of the agricultural greenhouse 100, or so as to form at least a portion of the rear side of the agricultural greenhouse 100. In this case, one surface 11 on which the numerous protrusions 14 are formed is the inner surface 11 of the ventilation sheet 10. This inner surface 11 is a side that defines the interior space of the agricultural greenhouse 100, and the other surface 12 located opposite the inner surface 11, i.e., the outer surface 12, is a side that is located outside the agricultural greenhouse 100. As shown in FIG. 7, at least one pillar member 101 of the multiple frame members is positioned adjacent to the inner surface 11 of the ventilation sheet 10 and extends along the inner surface 11. The ventilation sheet 10 is configured so that it can be rolled up and down along at least one pillar member 101. In the specific example shown in FIG. 7, a large number of protrusions 14 are formed on the inner surface 11 of the ventilation sheet 10.

[0073] FIG. 8 is a side view of a portion of the ventilation sheet 10 according to Modification 1 of the embodiment. In the ventilation sheet 10 according to Modification 1 shown in FIG. 8, the other surface 12 located opposite the one surface 11 has an uneven shape for diffusing light entering the agricultural greenhouse 100. Such an uneven shape may be any shape that can diffuse light entering the agricultural greenhouse 100, and is not particularly limited. For example, the uneven shape on the other surface 12 may be a so-called matte surface shape. A matte surface shape can be obtained, for example, by processing the other surface 12 so that its smoothness is reduced (to make it rough), thereby diffusing light entering the agricultural greenhouse 100. That is, a matte surface shape can be obtained, for example, by forming a large number of fine irregularities 16 on the other surface 12. The large number of fine irregularities 16 may be formed in a two-dimensionally regular pattern on the other surface 12, or may be formed randomly on the other surface 12. The numerous irregularities 16 on the mat-like surface shape may have a regular shape (for example, a pyramidal shape) or an irregular shape.

[0074] 8, when forming a large number of convex portions 14 on one surface 11 of the ventilation sheet 10 and forming an uneven shape for diffusing light on the other surface 12, a large number of concave portions are formed in advance on the surface of the roll corresponding to one surface 11 as described above, and fine concaves and convexes for forming the uneven shape are formed in advance on the surface of the roll corresponding to the other surface 12. Furthermore, the uneven shape on the other surface 12 may be formed by a method other than the method of transferring the shape of the roll as described above.

[0075] When the ventilation sheet 10 shown in Fig. 8 is used in the area shown in Fig. 3, for example, the other surface 12 having the uneven shape is the upper surface 12 of the ventilation sheet 10. Furthermore, when the ventilation sheet 10 shown in Fig. 8 is used in the area shown in Fig. 7, for example, the other surface 12 having the uneven shape is the outer surface 12 of the ventilation sheet 10.

[0076] 9 is a cross-sectional view showing a part of the ventilation sheet 10 according to Modification 2 of this embodiment. The ventilation sheet 10 according to Modification 2 has the above-mentioned many convex portions 14 formed on the front surface 11, and also has many convex portions 15 formed on the front surface 12 (back surface 12) opposite the front surface 11. This makes it possible to more effectively prevent blocking from occurring when the ventilation sheet 10 is rolled up and down.

[0077] The numerous protrusions 15 formed on the back surface 12 of the ventilation sheet 10 have the same characteristics as the numerous protrusions 14 formed on the front surface 11. Therefore, the numerous protrusions 15 have durability against the rubbing load.

[0078] As described above, the ventilation sheet 10 has a large number of hemispherical protrusions 14 formed on the surface 11, which can prevent blocking from occurring when the ventilation sheet 10 is rolled up and down, and the protrusions are durable against the friction load that occurs when the ventilation sheet 10 is rolled up and down.

[0079] Furthermore, because the ventilation sheet 10 is placed on and supported by multiple roof support members 103, the weight of the ventilation sheet 10 acts on the multiple roof support members 103. This means that the friction load tends to increase when the sheet is rolled up and down. Even in such cases, the numerous hemispherical protrusions 14 on the surface 11 are durable against the friction load, so the effect of suppressing blocking is maintained for a long period of time.

[0080] Furthermore, since the ventilation sheet 10 is arranged so as to be sandwiched between the multiple roof support members 103 and the multiple press bands 112, the operation of rolling up and rolling down the ventilation sheet is stable. On the other hand, since the ventilation sheet 10 comes into contact with the multiple roof support members 103 and the multiple press bands 112 during the rolling up and rolling down operations, the friction load is likely to increase further. Even in such cases, the ventilation sheet 10, which has a large number of hemispherical protrusions 14 formed on the surface 11, has the durability of the protrusions 14 against the friction load, and therefore can maintain the effect of suppressing the occurrence of blocking for a long period of time.

[0081] In the ventilation sheet 10 according to this embodiment, the outer diameter of each of the numerous protrusions 14 is within a range of 70 μm to 900 μm. 2 Since the number of the protrusions per contact is a value within the range of 5 to 170, the occurrence of blocking can be more effectively suppressed, and the durability of the protrusions against the rubbing load can be more effectively increased.

[0082] [Variations] The agricultural sheet according to the embodiment of the present invention has been described above, but the agricultural sheet according to the present invention is not limited to these embodiments and includes, for example, the following modified examples.

[0083] (A) Regarding the operation of rolling up and down the ventilation sheet In the above embodiment, the winding up and winding down of the ventilation sheet is performed by the winding motor 105, but instead of the winding motor 105, a rotating lever may be provided so that the worker can operate it manually.

[0084] (B) Regarding the back of the ventilation sheet The back surface (other surface 12) of the ventilation sheet may have a shape other than a mat-like uneven shape. The surface 12 of the ventilation sheet does not have to have an uneven shape.

[0085] (C) Agricultural greenhouses The ventilation sheet 10 according to the embodiment is used in row-type agricultural greenhouses 100, 100, but it may also be used in a single agricultural greenhouse that is not row-type but is arranged independently.

[0086] (D) Area where ventilation sheets are placed The ventilation sheet 10 according to the embodiment is disposed on a plurality of roof support members 103 between the top sheet 106 and the left side sheet 108L or the right side sheet 108R, is supported by these roof support members 103, and is configured so as to be capable of being rolled up and down along these roof support members 103, but may be disposed in other locations. For example, the ventilation sheet may be disposed in an area that entirely covers the plurality of roof support members 103.

[0087] (E) Direction of placement of ventilation sheets In the embodiment shown in Fig. 3, one surface 11 on which the numerous protrusions 14 are formed is arranged to face downward, but it may be arranged to face upward. Also, in the modified example shown in Fig. 7, one surface 11 on which the numerous protrusions 14 are formed is arranged to face the inside of the agricultural greenhouse 100, but it may be arranged to be located outside the agricultural greenhouse 100. [Explanation of symbols]

[0088] 10 Ventilation sheet 11 Surface of ventilation sheet 12 Back of ventilation sheet 13 Base 14 Convex part 15 Convex part 100 Agricultural greenhouses 103 Roof support member 106 Top sheet 108L left side seat 108R right side seat 110 Valley 112 Retaining band (an example of a retaining member)

Claims

1. A ventilation sheet for use in an agricultural greenhouse having a plurality of frame members, the ventilation sheet being arranged so as to be capable of being rolled up and down along a portion of the plurality of frame members, the ventilation sheet having a pair of surfaces, A ventilation sheet having a large number of protrusions formed on one of the pair of surfaces, each of the large number of protrusions having a hemispherical shape.

2. The ventilation sheet according to claim 1, the plurality of frame members include a plurality of roof support members arranged in areas corresponding to the roof of the agricultural greenhouse, The agricultural greenhouse has a top sheet that is placed on the plurality of roof support members and supported by the plurality of roof support members, and side sheets that form side surfaces of the agricultural greenhouse, the ventilation sheet is disposed on the plurality of roof support members between the top sheet and the side sheets, is supported by the plurality of roof support members, and is configured to be able to be rolled up and down along the plurality of roof support members; The one surface on which the numerous protrusions are formed is the underside facing the plurality of roof support members.

3. The ventilation sheet according to claim 2, The ventilation sheet has an upper surface, which is the other of the pair of surfaces, having an uneven shape for diffusing light entering the agricultural greenhouse.

4. The ventilation sheet according to claim 1, the ventilation sheet is arranged at a position that forms at least a part of a side surface of the agricultural greenhouse, and the one surface on which the numerous protrusions are formed is an inner surface of the ventilation sheet, the plurality of framework members include at least one framework member disposed adjacent to the inner surface of the ventilation sheet and extending along the inner surface; The ventilation sheet is configured to be capable of being rolled up and down along the at least one framework member.

5. The ventilation sheet according to claim 4, The ventilation sheet has an outer surface, which is the other of the pair of surfaces, that has an uneven shape for diffusing light entering the agricultural greenhouse.

6. The ventilation sheet according to any one of claims 1 to 5, The ventilation sheet, wherein the outer diameter of each of the numerous protrusions is within a range of 70 μm to 900 μm.

7. The ventilation sheet according to any one of claims 1 to 5, 4 mm in the ventilation sheet ２ The ventilation sheet has a number of the protrusions per unit area that is within a range of 5 to 170.

8. The ventilation sheet according to claim 6, 4 mm in the ventilation sheet ２ The ventilation sheet has a number of the protrusions per unit area that is within a range of 5 to 170.

9. The ventilation sheet according to claim 1, 2 or 4, A ventilation sheet having a large number of protrusions formed on the other surface of the pair of surfaces, each of the large number of protrusions having a hemispherical shape.

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