STEEL HEXAGONAL FRAME REEF Field of the Invention [00011 The present invention relates generally to a hexagonal frame artificial reef. 100021 In particularly, the invention relates to an artificial hexagonal frame reef which comprises a lower frame constituted of three concentric hexagonal frames (an inner frame, a middle frame and an outer or perimetric frame), vertical post frames (inner posts, middle posts and outer or perimetric posts) installed at respective corners of the three concentric hexagonal frames, two-step slanted or inclined frames extending substantially upwardly and inwardly from the perimetric or outer posts beyond upper ends of the middle posts and inner posts, a middle layer frame and an upper layer frame installed on the slanted frames in a hexagonal shape so as to form a pyramid-type artificial steel reef. A lower wall frame is installed between the lower frame and a middle layer frame and has a shape of window frame(s), and an upper wall frame is installed between the middle layer frame and the upper layer frame and has a shape of window frame(s). [00031 Such a construction effectively prevents the artificial reef from being sunk, improves fish gathering effects by providing a visual attracting effect, and improves the structural stability of the artificial steel reef. The construction also provides the benefit of gentle tidal current in the space created in the center portion of the artificial reef, which is essential for the growth and development of various aquatic plants and various marine fishes, and hence provides various aquatic plants and various marine fishes with optimum environmental conditions. Background Art 100041 Generally, an artificial reef is an artificial marine structure, which may be installed on the bottom of an ocean in the coastal areas of the sea so as to protect and develop marine resources. There are a variety of known artificial reefs such as a quadrangular-shaped artificial reef and a hemispherical-shaped artificial reef, which consist of concrete structure, an artificial steel reef, which consists of a series of steel frames, and an artificial reef made up of waste car body or waste ship's body, etc. [00051 In the coastal areas of Australia, the depth of water is shallow and the tidal current is slow. Also, the bottom of the sea consists mainly of sand-beds. The hemispherical-shaped artificial reef is best adapted to its environment. There are also known artificial steel reefs having a multi-layer framed structure. By way of an example, a 1 large number of pyramid-type artificial reefs which may reach 10m in height have been developed. [00061 Since the pyramid-type artificial reef may reach a height of 10m, various fishes, including not only snapper, trevallies and rear fishes which are demersal fishes but also yellowtail scads and pilchards which are bait fishes having a tendency to respond an artificial bait such as a lure, and juventile fishes, may be equally distributed along the height direction of the artificial reef. 100071 Since the conventional pyramid-type artificial steel reef comprises a simple framed structure of which a plurality of hexahedron frames are radially disposed in sequence on a concentric circle from the lower layer to the upper layer thereof, it cannot obtain a three-dimensional effect expressed by the reef and a sufficient 'shade' to be given in inner space of the reef. Because of this, it is hard to make various fishes cluster around the reef for a short time with various population. 100081 Since the flow of tidal current passing through the reef is not properly controlled by the steel frame, a strong flow of tidal current may be freely transferred to the inner space of the reef in coastal water where a comparatively powerful tidal current may occur. Because of this, it is hard to provide an active growing space, which is a spawning place, a hiding place, and a feeding ground for various marine organisms, in the center portion of the reef. 100091 Since the multi-layer framed structure is made by repeatedly connecting the steel frames in accordance with the hexahedron shape, enormous labor time and labor costs need to be expended for the manufacture of the artificial reef. Also, since the steel frames are simply disposed in accordance with a hexahedron shaped design, the structural strength of the reef may become weak. 100101 On the other hand, since the bottom of the sea in the coastal areas of Australia consists mainly of sand-beds, the pyramid-type artificial reef having a heavy weight framed structure may be easily and gradually sunk through the sea floor. Because the lower layer of the artificial reef takes up much room, the total function of the reef will deteriorate due to the settlement thereof. [00111 It is an aim of the present invention to provide an artificial reef which overcomes or ameliorates one or more of the above disadvantages. 2 Summary of the Invention 100121 In one broad form, the invention provides an artificial reef formed as a metal framework comprising: a generally pyramidal-shaped frame portion having a hexagonal outer shape in plan; and inclined wall frames located around the periphery of the frame portion and extending upwardly and inwardly. [00131 In a preferred embodiment, the artificial reef is a hexagonal frame reef formed as a multi-layer frame structure by using a plurality of steel frames, and comprises: a lower frame comprising an outer frame, a middle frame and an inner frame which are spaced concentrically and have a hexagonal shape, respective corner portions of the outer, middle and inner frames being connected with each other by a plurality of connecting frames members extending therebetween; a plurality of perimetric posts, a plurality of middle posts and a plurality of inner posts being vertically disposed at the corner portions of the outer frame, the middle frame and the inner frame, respectively, wherein the height of the middle posts is greater than that of the perimetric posts, and the height of the inner posts is greater than that of the middle posts, and lower portions of the posts extend a predetermined distance downwardly from the lower frame; first slanted frame members and second slanted frame members extending sequentially from upper ends of respective perimetric posts, wherein middle layer frame members extend between lower ends of the second slanted frame members, and upper layer frame members extend between upper ends of the second slanted frame members; an outer lower wall frame defined by the lower frame, the middle layer frame members and the first slanted frame members, the lower wall frame having a shape of window frame(s); and an outer upper wall frame defined by the middle layer frame members, the upper layer frame members and the second slanted frame members, the upper wall frame having a shape of window frame(s).. {00141 One or more marine algae sticking plates can be mounted onto the lower wall frame and/or the upper wall frame. 100151 Preferably, settlement preventing supporters are installed at lower ends of the respective perimetric posts and the inner posts. The lower portion of the middle posts extends downwards beyond the settlement preventing supporters at a predetermined 3 distance. 100161 Preferably, a tower frame having a shape of hexagonal post extends upwardly from the upper layer frame members. A plurality of tower supporting members extend slantly or at an inclination between the tower frame and the second slanted frame. [00171 As described above, the artificial hexagonal frame reef may be formed by connecting a plurality of steel frames together. Since the slanted frame members for connecting the posts and the wall-shaped frames are provided at the outer side of the reef, it provides a three-dimensional effect expressed by the reef and sufficient protected area or 'shade' in inner space of the reef. Consequently, it is possible to make various fishes cluster around the reef for a short time with various population. 100181 Furthermore, it can lead to improvement on the structural stability of the artificial steel reef and it is possible to accomplish a considerable reduction in labor time and labor costs to be spent for the manufacture of the artificial reef, by effectively disposing the steel frames. 100191 Furthermore, it is possible to provide an active growing space, which is a spawning place, a hiding place, and/or a feeding ground for various marine organisms, in the center portion of the reef, by creating hexagonal post-shaped space in the reef and by properly controlling the flow of tidal current passing through the reef due to the existence of the wall frames. 100201 In addition, it is possible to prevent the artificial reef from inking in the soft grounds such as the sand-bed layer and to prevent the functionality of the artificial reef from deteriorating, by extending the post frames required for the installation of the reef beyond the lower frame.at a predetermined distance and by installing the settlement prevent supporters at the lower ends of the posts. 100211 Finally, it can lead to improvement of the fish gathering effects by providing a visual attracting effect due to the installation of the hexagonal post-shaped tower frame at the upper end of the reef. Accordingly, various fishes including not only demersal fish and bait fish but also pelagic fish such as mahimahi, wahoo, mackerel and longtail tunas, school and spotted mackerel, yellowtail kingfish and Samson fish, etc. may gather in crowds in the artificial reefs and are likely to swim around the tower frame. 100221 The above object and other characteristics and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings. 4 Brief Description of the Drawings 100231 In the drawings: FIG. 1 is a perspective view of a hexagonal frame reef according to a preferred embodiment of the present invention; FIG. 2 is a partial enlarged perspective view of the reef as illustrated in FIG. 1; FIG. 3 is a front view of the hexagonal frame reef as illustrated in FIG. 1; FIG. 4 is a plan view of the hexagonal frame reef as illustrated in FIG. 1; FIG. 5 is a sectional view taken along the line A-A as shown in FIG. 3.; FIG. 6 is a perspective view of a tower frame according to one embodiment of the present invention; and FIG. 7 is a plan view of a hexagonal frame reef according to another embodiment of the present invention. Detailed Description of the Invention [0024] Hereinafter, the constitution of artificial hexagonal frame reef according to preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings FIGS. I to 7. 100251 Prior to proceeding to the more detailed description of the preferred embodiment according to the present invention, it should be noted that, for the sake of clarity and understanding of the invention, identical components which have identical functions have been identified with identical reference numerals throughout the different views which are illustrated in each of the attached drawing Figures. The terms 'frames' and 'frame members' may be used to refer to the same components. 100261 Referring to FIGS. 1 to 4, the hexagonal frame reef 10 according to the preferred embodiment of the present invention comprises a lower frame 1, a middle layer frame 2 and an upper layer frame 3 which stand in a pyramid formation. The lower frame I is a basic frame for constructing the hexagonal frame reef 10. 100271 If an artificial steel reef according to the prevent invention is formed as a hexagonal frame structure, it is possible to realize a three-dimensional shape with same visual effect from every angle, compared with a conventional pyramid-type reef having a rectangular shape. Consequently, this leads to improvement of the fish gathering effects in comparison with a conventional pyramid-type reef having a rectangular shape. Furthermore, this leads to improvement on the structural stability of the artificial steel reef. 100281 Under the circumstances described above, it would be appreciated by one of 5 ordinary skill that any type of suitable design technique may be used for installing a frame structure. For example, it may be appreciated that an octagonal frame structure can be employed as an artificial reef instead of the hexagonal frame structure. However, if the octagonal frame structure is used for the manufacture of the artificial reef 10, the number of steel frames and connecting elements disposed between the steel frames are greatly increased, thereby resulting in a considerable increase in costs to be spent for the manufacture of the artificial reef 10. Accordingly, in the present invention, a hexagonal frame structure is used for the manufacture of artificial steel reef 10 with especially considering the functionality of the manufacturing cost of the artificial reef. 100291 As best seen in FIG. 5, the lower frame I is a basic frame of the reef 10. The lower frame 1 includes a perimetric or outer frame 11, a middle frame 12 and an inner frame 13, in which the frame members of these frames 11, 12 and 13 are radially disposed in sequence on respective concentric circles, thereby resulting in the formation of a hexagonal shape. Corner portions of the frames 11, 12 and 13 are integrally connected with each other by means of a plurality of connecting frames 14 extending there between. 100301 A plurality of peripherally-located or perimetric posts or post frames 5, a plurality of middle posts or post frames 6 and a plurality of inner posts or post frames 7 are vertically disposed at six corner portions of the outer or perimetric frame 11, the middle frame 12 and the inner frame 13, respectively. 100311 Accordingly, the connecting frames 14 meet with the post frames 5,6,7 in a criss-cross pattern at the six corner portions of the perimetric frame 11, the middle frame 12 and the inner frame 13, respectively. Due to this structure, the lower frame 1 can supply the artificial reef 10 with a strong substructure. 100321 Preferably, the height of the middle post frame 6 is greater than that of the perimetric post frame 5 and the height of the inner post frame 7 is greater than that of the middle post frame 6, and thereby resulting in the formation of a pyramid-type reef structure. At this time, lower portions of the post frames 5,6,7 extend downward from the lower frame 1 at a predetermined distance so as to install and support the artificial reef 10. 100331 A first slanted frame 8 and a second slanted frame 9 extend substantially upward from an upper end of the perimetric post frame 5 in sequence so that the post frames 5,6,7 are strongly supported by the lower frame I and the slanted frames 8,9. 100341 As shown in FIG. 3, the first slanted frame 8 is slanted at an angle of about 70 degrees and the second slanted frame 9 is slanted at an angle of about 35 degrees. However, it should be appreciated by one of ordinary skill that the height of the post 6 frames 5, 6, 7 and the angle of inclination of the slanted frames 8, 9 may vary based on application. 100351 Since the first slanted frame 8 and the second slanted frame 9 extend substantially upward from an upper end of the perimetric post frame 5 in sequence, the frame members 5,8,9 are arranged in pairs become a form of umbrella ribs at an angle of 60 degrees on the total hexagonal frame structure, thereby resulting in the formation of a strong outer periphery frame. 100361 The middle layer frame 2 extends between lower ends of the second slanted frame 9 and the upper layer frame 3 extends between upper ends of the second slanted frame 9. As best seen in FIG. 2, a plurality of reinforcement bars for reinforcing the strength characteristics of the reef 10 may usually extend between the inner post frames 7 or between the inner post frame 7 and the adjacent middle post frame 6. 100371 Due to the structure as described above, as shown in FIG. 5, a hexagonal post shaped space is created at a center portion of the artificial reef 10 according to the present invention. This space is defined by the inner frame 13, six inner post frames 7 and the reinforcing bar 17. Consequently, it is possible to provide a space required to allow the tidal current to flow and aquatic plants to move there into so that various marine algae or the young of shellfish effectively grow therein. 100381 A lower wall frame 15 is installed in an outer surface defined by the lower frame 1, the middle layer frame 2 and the first slanted frame 8. The lower wall frame 15 has a shape of a window frame. Likewise, an upper wall frame 16 is installed in an outer surface defined by the middle layer frame 2, the upper layer frame 3 and the second slanted frame 9. The upper wall frame 16 has a shape of window frame. 100391 The lower wall frame 15 is provided with a plurality of horizontal reinforcing frames 15a extending between the first slanted frames 8 and a plurality of vertical reinforcing frames 15b between the horizontal reinforcing frames I5a. Likewise, the upper wall frame 16 is provided with a plurality of horizontal reinforcing frames 16a extending between the second slanted frames 9 and a plurality of vertical reinforcing frames 16b between the horizontal reinforcing frames 16a. The middle layer frame 2 disposed between lower ends of the upper wall frame 16 is adapted to act as a lower horizontal reinforcing frame. 10040] The wall frames 15,16 can act as an obstacle for blocking the tidal current to be introduced into the reef 10 in appropriate ways so as to attenuate the tidal current. This leads to the benefit of gentle tidal current in the space essential for the growth and 7 development of various aquatic plants and various marine fishes, which is created in the center portion of the artificial reef 10. Consequently, it can provide various aquatic plants and various marine fishes with the optimum environment conditions. [00411 It should be appreciate by one of ordinary skill that any type of suitable design technique may be used for installing the lower wall frame 15 and the upper wall frame 16. It is preferred that a marine algae sticking plate 20 is mounted onto the lower wall frame 15 and the upper wall frame 16. [00421 The marine algae sticking plate 20 provides the artificial reef 10 with a sufficient surface area to allow all marine algae to be attached thereto and grow thereon. Furthermore, the marine algae sticking plate 20 can function to strengthen the blocking effect and the control effect of the tidal wave propagation due to the existence of the lower wall frame 15 and the upper wall frame 16. Furthermore, the marine algae sticking plate 20 can function to provide the internal space of the artificial reef 10 with more shade area adapted for growth in marine algae. The marine algae sticking plate 20 is preferably made of metal, but it can be made of a concrete as needed. 100431 FIGS. I to 4 show the state that the marine algae sticking plate 20 is only mounted to the upper wall frame 16. In comparison, FIG. 7 shown the state that the marine algae sticking plate 20 is mounted to the lower wall frame 15 and the upper wall frame 16. In detail, one marine algae sticking plate 20 is mounted to the upper wall frame 16 and two marine algae sticking plate 20 are mounted to the lower wall frame 15. 100441 It should be appreciated by one of ordinary skill that any type of suitable design technique may be used for installing the marine algae sticking plate 20. For example, it may be appreciated that the marine algae sticking plate 20 is only mounted to the lower wall frame 15 instead of the upper wall frame 16. Also, it will be understood by those skilled in the art that the number and the installation position of the marine algae sticking plate 20 can be optionally controlled on the basis of its application. The marine algae sticking plate 20 is more preferably installed in grid pattern space defined by the horizontal reinforcing frames 15a,16a and the vertical reinforcing frames 15b,16b, respectively. [00451 FIGS. 1 to 3 show other important constitutional elements of the artificial reef 10 of the preferred embodiment. As shown in FIG. 1 to 3, a settlement preventing supporter 5a is installed at a lower end of the perimetric post frame 5 and a settlement preventing supporter 7a is installed at a lower end of the inner post frame 7. The lower portion of the middle post frame 6 extends downwards beyond the settlement preventing 8 supporter 5a,7a at a predetermined distance. Due to this structure, it is possible to keep the artificial reef 10 in a safe and stable condition. 100461 As the lower end of the middle post frame 6 is forcibly inserted into a sea floor comprising a sand-bed layer to a predetermined depth, the artificial reef 10 can usually stand in a safe and stable condition. Since the settlement preventing supporter 5a,7a provided at the lower portions of the perimetric post frame 5 and the inner post frame 7, respectively, ensure a sufficient ground surface area against the sea floor, they can effectively prevent the artificial reef 10 from being sunk. 100471 As shown in FIGS. I to 3 and 6, a tower frame 4 having a shape of hexagonal post extends upwards from the upper layer frame 3. A plurality of tower supporting members 18 extend at a slant or inclination between the tower frame 4 and the second slanted frame 9. [0048] The tower frame 4 includes six vertical reinforcing frames 4a which upwardly extend from corners of the upper layer frame 3, and a plurality of horizontal reinforcing frames 4b extending between the upper frames 3. These horizontal reinforcing frames 4b are spaced with each other at a predetennined distance. Two rows of tower supporting members 18 extend at a slant or inclination between the tower frame 4 and the second slanted frame 9. A plurality of horizontal reinforcing bars 19 extend between the tower supporting members 18. 100491 The tower frame 4 may function to gather almost all type of pelagic fish including mahi mahi, wahoo, mackerel and longtail tunas, school and spotted mackerel, yellowtail kingfish and Samson fish, etc., which mainly live in the coastal areas. Pelagic fish gathering about the tower frame 4 is likely to swim around the tower frame 4. 100501 Demersal fishes may be gathered about the lower frame I of the hexagonal frame reef 10. Mesopelagic fish such as bait fish may be gathered about the body portion of the hexagonal frame reef 10 including the lower wall frame 15 and the upper wall frame 16. The tower frame 4 is applicable for almost all type of migratory fish so that it can provide the optimum growing conditions suitable for various fishes. 100511 In the embodiment as described above, the lower frame 1, the middle layer frame 2, the upper layer frame 3, the post frames 5,6,7 and the slanted frame 8,9 may be usually manufactured by using H--shape steel. The wall frames 15,16, the tower frame 4, the reinforcing bars 17,19 and the tower supporting members 18 may be preferably manufactured by using a "7" shaped or "i-"shaped angle frame so that it is possible to emphasize a three-dimensional effect of the artificial reef 10. 9 10052] It should be appreciate by one of ordinary skill that the quality of the material or a shape of the frame as described above can be changed as needed by the manufacturer of the artificial reef 10 on the basis of its application. Preferably, the frames are integrally connected with each other by using the welding process, like the conventional metal reef. It may be appreciated that the frames are connected with each other by using a bolt and a nut. Alternatively, the frames can be connected with each other by using the riveted joint. 10053] It is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the above description or illustrated in the drawings. 100541 The invention is capable of other embodiments and of being practiced and carried out in various ways by modifying the structure of artificial reef as needs of manufacturer of the artificial reef on the basis of its application. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. 100551 While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 100561 The term "comprise" and variants of that term such as "comprises" or comprising" are used herein to denote the inclusion of a stated integer or integers but not to exclude any other integer or any other integers, unless in the context or usage an exclusive interpretation of the term is required. 100571 Reference to prior art disclosures in this specification is not an admission that the disclosures constitute common general knowledge in Australia. 10 100581 Reference numerals in the drawings 1 lower frame 2: middle layer frame 3 : upper layer frame 4: tower frame 4a: vertical reinforcing bar 4b: horizontal reinforcing bar 5 : perimetric post frame 5a,7a: settlement preventing supporter 6: middle post frame 7: inner post frame 8: first slanted frame 9: second slanted frame 10: hexagonal frame reef 11 : perimetric frame 12 : middle frame 13 : inner frame 14: connecting frame 15 : lower wall frame I5a, I 6a: horizontal reinforcing frame 15b,16b : vertical reinforcing frame 16 : upper wall frame 17,19 : reinforcing bar 18: tower supporting member 20: marine algae sticking plate 11