Abstract:
A container ( 12 ) for aeration of a substrate ( 60 ) supporting a plant ( 62 ) with the substrate ( 60 ) being received in a cavity ( 27 ) of the container ( 12 ) so as to bury a device ( 14 ) positioned in the cavity ( 27 ) such that gas can be supplied from the device ( 14 ) to the substrate ( 60 ). The device ( 14 ) comprises a body ( 40, 42 ) having a peripheral wall ( 44 ) defining an inner cavity ( 50 ). The peripheral wall ( 44 ) has a portion ( 52 ) permeable to gas such that a gas can flow therethrough from the inner cavity ( 50 ) of the body ( 40, 42 ) to an exterior of the device ( 14 ). A gas permeability of the body ( 40, 42 ) decreases as a function of a vertical orientation of the body ( 40, 42 ). The body ( 40, 42 ) has an inlet ( 49, 71 ) adapted to receive a gas to fill the inner cavity ( 50 ). The device ( 14 ) is buried in a predetermined position with respect to the vertical orientation, such that greater amounts of gas can be supplied to the substrate ( 60 ) relatively to a depth of the device ( 14 ).

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to plant-growing equipment. More precisely, the invention describes an apparatus to enhance aeration of a substrate supporting a plant.  
           [0003]    2. Description of the Prior Art  
           [0004]    Plants require fundamental elements in order to grow. (These elements are water, various nutrients, and air (more specifically, oxygen). Usually, water and nutrients are well supplied to the plant.  
           [0005]    The roots anchor a plant to a substrate, and extract the nutrients therefrom. Artificial substrates are now widely used. They replace common soil. Unfortunately, soil oxygenation is often inadequate in many substrates. A lack of suitable oxygenation can prevent the proper development of a plant. The lack of oxygenation is exacerbated if the particles of the substrate are relatively small. A common approach to the problem is to use substrates that have large particles, but such substrates are costly. The bottom of a typical plant-growing container is often subject to a lack of oxygenation. As roots reside in the bottom of plant-growing containers, the proper oxygenation of bottom portions of containers can help in optimizing the development of plants.  
           [0006]    In order to overcome the under-oxygenation of the roots, various solutions have been tested. One solution consists in creating aeration holes on the walls of plant-growing containers. These aeration holes then allow the natural airflow and thus the oxygenation of bordering areas of a substrate. For instance, U.S. Pat. No. 4,528,774, issued to Skaife on Jul. 16, 1985, and U.S. Pat. No. 954,440, issued to Klemm on Apr. 12, 1910, each describe plant-growing containers having perforations on their lateral surfaces supporting the substrate.  
           [0007]    British Patent No. 403,460, issued to Roberts et al. on Dec. 28, 1933, U.S. Pat. No. 4,173,098, issued to Smith on Nov. 6, 1979, and U.S. Pat. No. 4,236,351, issued to Smith on Dec. 2, 1980, each disclose plant-growing containers defining a cavity below a substrate section. The cavity and the substrate section are separated by a perforated disk allowing an air supply to the bottom of the substrate section. Cylindrical tubes extend through the substrate section to reach the cavity and supply water thereto. Ambient air can also circulate through the cylindrical tubes to reach the cavity. Furthermore, in British Patent No. 403,460, the cylindrical tubes are perforated in their portion embedded in the substrate section, such that the substrate can be oxygenated through these perforations.  
           [0008]    German Patent No. 806,918, issued on Jun. 21, 1951 to Kiel, and U.S. Pat. No. 1,952,597, issued to Lizzola on Mar. 27, 1934, both describe devices that are securable to an inner wall of plant-growing containers. These devices are perforated and allow the oxygenation of the substrate. These devices can take various shapes, including an upwardly flaring cone.  
           [0009]    U.S. Pat. No. 3,958,366, issued to Meyers on May 25, 1976, discloses a plant-growing container that permits the irrigation of the substrate as well as the aeration thereof. The aeration is effected by cylindrical tubes that project from the exterior surface of the plant-growing container towards the substrate. These cylindrical tubes are perforated, such that air can be supplied to the substrate.  
           [0010]    U.S. Pat. No. 4,175,356, issued to Allen on Nov. 27, 1979, describes a cylindrical tube having pointy ends to be inserted into the substrate of a plant-growing container. The cylindrical tube defines an inner cavity on a full length thereof, and the peripheral surface of the cylindrical tube is perforated, such that the substrate into which the cylindrical tube is inserted can be oxygenated by the air contained in the inner cavity. The pointy ends of the cylindrical tube are also perforated, such that ambient air can fill the inner cavity. The cylindrical tube is simply inserted into the substrate and the pointy ends facilitate the insertion.  
           [0011]    U.S. Pat. No. 5,692,338, issued on Dec. 2, 1997 to Rose, describes a device similar to that of U.S. Pat. No. 4,175,356 in that the device can be inserted into the substrate by a pointy end. However, the device disclosed in U.S. Pat. No. 5,692,338 is shaped as a square-based pyramid, inverted when inserted into the substrate.  
           [0012]    In the above-cited references, the diffusion rate within the aeration structure cannot be modified, as the devices are passive (only provide diffusion of air). However, considering that the aeration demand may vary in time because of an increased soil biological activity, of the evolution of the physical properties of the soil, or of a more active root growth, devices that will improve the aeration process rapidly and efficiently must be introduced.  
         SUMMARY OF THE INVENTION  
         [0013]    Therefore, it is an aim of the present invention to provide a new plant-growing container.  
           [0014]    It is a further aim of the present invention to provide a method for assembling the new plant-growing container of the present invention.  
           [0015]    Therefore, in accordance with the present invention, there is provided a device for aeration of a substrate supporting a plant, comprising a body having a peripheral wall with an inner surface and an outer surface, the inner surface of the peripheral wall defining an inner cavity of the body, the peripheral wall having a portion permeable to gas such that a gas can flow therethrough from the inner cavity of the body to an exterior of the body, a gas permeability of the peripheral wall of the body increasing along a given orientation of the body, the body having an inlet adapted to allow a gas to fill the inner cavity, the body being adapted to be at least partly buried in a substrate with the substrate being in contact with the outer surface of the body such that the gas can flow from the inner cavity through said portion of the peripheral wall to the substrate, wherein the device is at least partly buried in the substrate with the body in a predetermined position with respect to said given orientation, such that amounts of gas supplied to the substrate along the body increases with a depth of the device in the substrate.  
           [0016]    Also, in accordance with the present invention, there is provided a device for aeration of a substrate supporting a plant, comprising a body having a peripheral wall with an inner surface and an outer surface, the inner surface of the peripheral wall defining an inner cavity of the body, the peripheral wall having a portion permeable to gas such that a gas can flow therethrough from the inner cavity of the body to an exterior of the body, the body being adapted to be at least partly buried in a substrate with the substrate being in contact with the outer surface of the body such that the gas can flow from the inner cavity through said portion of the peripheral wall to the substrate, the body having at least one port in fluid communication with the inner cavity, and a pressure source connected to the at least one port of the body for creating a pressure differential between the inner cavity and surroundings of a surface of the substrate to enhance a gas supply to the substrate through said portion of the peripheral wall.  
           [0017]    Further in accordance with the present invention, there is provided a system for aeration of a substrate supporting a plant, comprising a container having a wall defining a cavity adapted to receive a substrate therein, and an aeration device as described above, the aeration device being positioned in the cavity of the container, wherein a substrate is received in the cavity of the container so as to bury at least partially the aeration device positioned in the cavity such that gas can be supplied from the aeration device to the substrate.  
           [0018]    Still further in accordance with the present invention, there is provided a method for providing aeration to a plant-supporting substrate, comprising the steps of i) providing a container having a first cavity and a funnel having perforations extending through a wall thereof, ii) placing the funnel in an inverted position in the first cavity of the container so as to form a second cavity therebetween, and iii) filling the first cavity of the container outwardly of the funnel with a plant-supporting substrate with a maximal level of substrate being below an open end of the funnel, such that air can be supplied from surroundings of the container to the second cavity and through the perforations to the substrate.  
           [0019]    Still further in accordance with the present invention, there is provided a method for providing enhancing aeration to a plant-supporting substrate, comprising the steps of i) providing a body having a gas permeable peripheral wall defining an inner cavity, ii) burying the body at least partially in a substrate, and iii) creating a pressure differential between the inner cavity and the substrate to enhance a supply of air from the inner cavity to the substrate. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof and in which:  
         [0021]    [0021]FIG. 1 is a vertical cross-sectional view of a plant-growing container in accordance with the present invention;  
         [0022]    [0022]FIG. 2 is a vertical cross-sectional view of the plant-growing container provided with additional components and features; and  
         [0023]    [0023]FIG. 3 is a vertical cross-sectional view of an aeration apparatus in accordance with another embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    Referring to the drawings, and more particularly to FIG. 1, a plant-growing container in accordance with the present invention is generally shown at  10 . The plant-growing system  10  has a container  12  and an aeration device  14 . The container  12  is a typical container defining an inner cavity accessible from an open top end thereof, such that a substrate can fill the inner cavity so as to support a plant. More precisely, the container  12  is shown having a base  20  and a peripheral wall  22 . The peripheral wall  22  has an inner surface  24  and an outer surface  26 , and defines an inner cavity  27  of the container  12  with the base  20 . A top end  28  of the container  12  is open, such that the inner cavity  27  can be accessed. Although the container  12  is illustrated as being of inverted frusto-conical shape, it is obvious that other shapes of container can be used in the present invention. For instance, the container  12  may have a cylindrical shape, a rectangular prism shape, etc.  
         [0025]    The aeration device  14  is shown having a lower flared portion  40  and an upper cylindrical portion  42 . The flared portion  40  and the cylindrical portion  42  are integral, such that the aeration device  14  is shaped as an inverted funnel. The aeration device  14  has a peripheral wall  44  with an inner surface  46  and an outer surface  48 . The inner surface  46  defines an inner cavity  50 , and the aeration device  14  is open at top and bottom ends thereof, such that the inner cavity  50  can be accessed thereby. The peripheral wall  44  defines a plurality of perforations  52  that extend from the inner surface  46  to the outer surface  48 . The aeration device  14  is shown centered in the container  12 , but may obviously be off-center.  
         [0026]    The aeration device  14  is positioned in the container  12  to form the plant-growing system  10 , with the flared portion  40  sitting on the base  20  of the container  12 . A top end  49  of the cylindrical portion  42  preferably extends above the top end  28  of the container  12 . Once the aeration device  14  is positioned in the container  12 , a substrate  60  fills the volume of the inner cavity  27  of the container  12  that is not occupied by the aeration device  14 . Therefore, the inner cavity  50 , also known as chamber, of the aeration device  14  remains filled with air while the container  12  has the substrate  60  therein. Plants  62  are supported by the substrate  60 . As the open end  49  of the cylindrical portion  42  is preferably above the top end  28  of the container  12 , the open end  49  will not be buried or clogged by the substrate  60 . Therefore, air in the inner cavity  50  of the aeration device  14  can circulate outwardly through the perforations  52  so as to supply air to the substrate  60  and the plants  62 . Ambient air is free to circulate through the cylindrical portion  42  by the open end  49 , such that fresh air can be supplied to the substrate  60  and the plant  62  through the inner cavity  50 . The device  14  may also be completely buried in the substrate  60 , and air contained in the device  14  will be diffused to the substrate  60 , provided that the substrate  60  is not saturated with water. If desired, a tubing (not shown) can be connected to the top end  49  to enhance the air exchange through the aeration device  14 .  
         [0027]    The configuration of the aeration device  14  enables air to be provided to air-depleted areas (anaerobiosis) of the plant-growing container  10 . Air-depleted areas are typically created in bottom parts of containers, because the substrate is more compact in the bottom of containers as it bears the weight of upper layers of substrate and of the plants. Therefore, the growth of the roots located in the bottom of typical containers will not be optimized. The flared portion  40  of the aeration device  14  provides a gradually increasing amount of air-exchange areas, i.e., the perforations  52 , as a function of the depth of the aeration device  14  in the container  12 . Furthermore, the flared portion  40  will occupy a greater volume of the container  12  with respect to the volume of the substrate  60  as a function of the depth. In other words, the deeper the substrate  60  is positioned in the container  12 , the more the aeration device  14  will supply air thereto. Therefore, the perforations  52  help balance the presence of air in the substrate  60 .  
         [0028]    Although providing perforations in a funnel and inserting the funnel in an inverted position into a container is the preferred way of fabricating the plant-growing system  10 , other fabrication methods are contemplated. For instance, providing a funnel in a porous material allowing air circulation therethrough is another alternative in accordance with the present invention.  
         [0029]    The aeration device  14  advantages the bottom part of the plant-growing system  10  and thus optimizes the root development through the substrate volume of the container  12 . An appropriate ratio between the varying diameter of the flared portion  40  and the diameter of the container  12  must be selected in order to effectively provide a homogeneous concentration of air in the substrate  60 . Also, the slope of the flared portion  40  must be wisely chosen. For a fixed density of perforations  52  in the peripheral wall  44 , a small slope will allow less oxygenation than an important slope. An important slope will lead to a larger portion of the container  12  being occupied by the aeration device  14 , whereby less substrate  60  can be retained in the container  12 . It is therefore important to adapt the aeration device  14  in order to efficiently provide air to the substrate  60 . The density of the perforations  52  in the peripheral wall  44  of the aeration device  14  will also be chosen to meet specific plant needs. It is pointed out that, although the flaring configuration of the aeration device  14  is preferred for the above-described reasons, the important feature is to provide an increasing amount of air-exchange surface with the increasing depth.  
         [0030]    Referring to FIG. 2, the plant-growing system  10  is shown provided with optional elements that enhance the aeration of the substrate  60 . Channels  70  are positioned on the base  20  of the container  12  and are in fluid communication with the aeration device  14  through inlets  71 . Although two channels  70  are illustrated in FIG. 2, it is obvious that a varying number of channels  70  can be provided. The channels  70  extend between the aeration device  14  and the peripheral wall  22  of the container  12 . Therefore, as shown in FIG. 2, ends  72  of the channels  70  can be connected to an air source, such as supply hose  74 . For instance, the ends  72  can be tapped for operating engagement with a hose adapter (not shown). The channels  70  are shown having perforations  76  such that air flowing through the channels  70  can be directed to the substrate  60 . The supply hose  74  creates a flow of air in the inner cavity  50  of the aeration device  14 .  
         [0031]    The open end  49  of the cylindrical portion  42  allows air to exit from the inner cavity  50 . A flow control device  80 , such as a venturi or a control valve, is shown mounted to the open end  49  of the cylindrical portion  42  so as to control the exit of air flowing through the inner cavity  50  of the aeration device  14 . In the case where the flow control device  80  is an outlet control valve, a positive pressure can be accumulated in the inner cavity  50  via the supply hose  74  to accelerate the transfer of air to the substrate  60  and the roots of the plant  62 . Alternatively, a negative pressure can be created by having a suction device (not shown) connected to the supply hose  74  to cause a flow of air to the inner cavity  50 , and force air exchange with the substrate  60 . The circulation of air enables an air supply to the substrate  60  by convection of air, as opposed to diffusion of air for containers without forced-air circulation. A venturi can also be used to create a negative pressure in the inner cavity  50  without the need for a pressure source to be connected to the device  14 . This inner suction will cause an upward motion of the air in the device  14 , thereby enhancing the air exchange between the inner cavity  50  and the substrate  60 .  
         [0032]    Referring to FIG. 3, an aeration apparatus in accordance with another embodiment of the present invention is generally shown at  100 . The aeration apparatus  100  has the aeration device  14  as described for FIGS. 1 and 2, with a bottom plate  102  positioned on a bottom surface thereof, so as to define a bottom portion of the inner cavity  50 . Like numerals between FIGS.  1 - 2  and FIG. 3 will designate like elements.  
         [0033]    The aeration apparatus  100  is positioned directly in a substrate  60 . Therefore, the aeration apparatus  100  can be used in fields rather than in containers, to supply air to substrates. A plurality of the aeration apparatuses  100  can be connected to a same pressure source (not shown) in a network of aeration apparatuses  100  in a field.  
         [0034]    The aeration device  14  can be fabricated and sold separately from the container  12 . The aeration device  14  is generally made of plastic or any other substantially rigid material that is preferably moldable. Alternatively, it can be made of a semi-rigid geotextile.  
         [0035]    If the aeration device  14  is to be sold separately from the container  12  and has the options illustrated in FIG. 2, the channels  70  can either be molded directly in the container  12 , or can include tubing (not shown) connected to the aeration device  14  and adapted to be secured to through bores (not shown) in the peripheral wall  22  of the container  12 . The plant-growing system  10  can be used for domestic uses, industrial uses and in nurseries.