Water purifying device

Abstract

A water purifying device 10, which purifies water while causing blades 50 that extend radially in a water surface direction from a rotating shaft 12 erected perpendicular to a water surface 64 to float and rotate on the water surface 64, comprises a floating body 17 that is disposed below the rotating shaft 12, a floating body housing 14 that surrounds the floating body 17 and is rotated by the rotating shaft 12, rods 18 that extend radially from the floating body housing 14, and the blades 50, provided on the rods 18, wherein a water passage 53 through which water pushed by the blades 50 flows is provided between the blades 50 and the floating body housing 14.

Description

Water purification equipment

[0001] The present invention relates to a water purification device for purifying water in large aquariums, ponds, marshes, lakes, estuaries, inlets, etc.

[0002] In water bodies with little or no current, such as large aquariums, ponds, marshes, lakes, estuaries, and inlets, decay and oxygen deficiency become problems. Various measures have been proposed to resolve these issues. Among these, a water purification device with excellent energy-saving performance is known (see, for example, Patent Document 1 (Figure 2)).

[0003] Patent Document 1 will be explained with reference to the following figure. Figure 8 is a diagram illustrating the basic structure of a conventional water purification device. The water purification device 100 comprises a float 101, a base 102 supported by the float 101, a motor 103 supported by the base 102, a disk 105 supported by a rotating shaft 104 of the motor 103, and a plurality of blades 106 provided on the underside of the disk 105. The plurality of blades 106 are arranged radially around the rotating shaft 104. The disk 105 is hollow and also serves as a float.

[0004] When the disk 105 is rotated by the rotating shaft 104, the blades 106 generate a current indicated by the arrow (111) on the water surface 107. In conjunction with the current indicated by the arrow (111), a cylindrical current (arrow (112)) is generated. This cylindrical current maintains water circulation and eliminates putrefaction and oxygen deficiency.

[0005] The rotating shaft 104 rotates at a rotational speed of 3 to 6 revolutions per minute. The rotational speed of a general-purpose electric motor is 1,450 to 1,500 revolutions per minute. In contrast, a rotational speed of 3 to 6 revolutions per minute is an extremely slow speed. An advantage of an extremely slow speed is that only a very small amount of electrical energy is required to be supplied to the motor 103.

[0006] However, because the speed is so low, the centrifugal force exerted by the blades 106 is small. Therefore, the flow (arrows (113) and (114)) inside the cylindrical flow is inevitably weak. In addition, the flows indicated by arrows (113) and (114) hit the disk 105 after rising and remain there for a while. This retention further weakens the upward movement, thereby reducing the performance of the water purification device 100.

[0007] However, even in ultra-low speed water purification devices, an increase in circulation flow is required, and a high performance structure is desirable.

[0008] Patent No. 3360075

[0009] An object of the present invention is to provide a structure that can further improve performance in a water purification device that rotates at an ultra-low speed.

[0010] The inventors have tried various solutions and have succeeded in establishing a structure that can solve the problem. The process of this success will be explained with reference to Figures 1(a) and 1(b).

[0011] Fig. 1(a) is a diagram of a conventional water purification device 100. In Fig. 1(a), the bottom surface of the disk 105 obstructs the upward flow (arrow (113)). As a first measure, the diameter of the disk 105 is reduced.

[0012] Centrifugal force is mrω ２ (m: mass, r: radius, ω: angular velocity). To increase the centrifugal force, the blades 106 are separated from the disk 105 and placed outside. That is, the radius r is increased as a second measure. Because the blades 106 interfere with the float 101, the float 101 is removed.

[0013] As a result of taking the above first and second measures, the water purification device 10 shown in Figure 1(b) was obtained. As shown in Figure 1(b), the water purification device 10 comprises a base 11 placed in the air, a motor 13 with a reducer fixed to the base 11 with a rotating shaft 12 extending downward, a float housing 14 fixed to the rotating shaft 12, a float 17 stored in the float housing 14, a rod 18 extending radially from the float housing 14, and blades 50 attached to the rod 18.

[0014] The float 17 is housed in the float housing 14, sandwiched between the upper housing part 15 and the lower housing part 16. In principle, the base 11 is pulled by a plurality of wires 19 to prevent rotation. The wires 19 may be ropes or strings.

[0015] When the blades 50 are rotated by the rotating shaft 12, centrifugal force generates a flow indicated by the arrow (81) on the water surface 64. This flow corresponds to a "river flowing radially from the center of rotation of the blades 50." Focusing on the blade 50 on the left side of the drawing, the blade 50 moves from the back of the drawing to the front. The water pushed by the blade 50 escapes from the outer end 51 and inner end 52 of the blade 50. In particular, the water escaping from the inner end 52 passes through the water passage 53 formed between the blade 50 and the float housing 14, and appears to flow from the front of the drawing to the back. "Appearance" refers to the appearance of water flowing if the blade 50 were stationary.

[0016] This flow in the water passage 53 promotes the flow indicated by the arrow (82). In addition, the flow indicated by the arrow (82) is active because there is no obstruction above (Fig. 1(a), disk 105). As a result, the flow indicated by the arrow (82) is significantly larger than the flow indicated by the arrow (113) in Fig. 1(a), thereby improving the water circulation performance.

[0017] Based on the above findings, the present invention is as follows: The invention according to claim 1 is a water purification device that rotates blades that extend radially toward the water surface from a rotating shaft that is erected perpendicular to the water surface, floating on the water surface and purifying water by raising a river that flows radially from the center of rotation of the blades to the water surface without splashing up the water on the surface, the water purification device comprising a float placed below the rotating shaft, a float housing that surrounds the float and is rotated by the rotating shaft, a rod that extends radially from the float housing, and the blades attached to the rod, and a waterway that allows water pushed by the blades to flow is provided between the blades and the float housing.

[0018] In the invention according to claim 1, a water passage is provided between the impeller and the floating body housing, which increases the amount of circulating water compared to conventional water purifiers, improving the performance of the water purifier. In other words, the present invention provides a structure that improves the performance of a water purifier that rotates at an ultra-low speed.

[0019] (a) is a diagram showing a comparative example, and (b) is a diagram showing an embodiment of the present invention. An exploded view of a water purifier according to the present invention. (a) is a plan view of the rod and blades, and (b) is a cross-sectional view along line b-b in (a). A front view of a water purifier according to the present invention. (a) is a plan view (partial view) of a pond in which a water purifier according to the present invention is floating, and (b) is an enlarged view of part b in (a). (a) to (c) are diagrams explaining the operation of the water purifier. (a) to (g) are diagrams explaining modified examples. A diagram explaining the basic structure of a conventional water purifier.

[0020] An embodiment of the present invention will be described below with reference to the accompanying drawings.

[0021] To facilitate understanding of the water purification device 10 according to the embodiment, the components of the water purification device 10 will be described using an exploded view.

[0022] [Elements Constituting the Water Purification Device] As shown in Figure 2, the water purification device 10 comprises a motor with a reducer 13, a base 11, a boss plate 22 with a boss 21, an upper Y-shaped housing 15, a float 17, a lower Y-shaped housing 16, three rods 18, and three blades 50. For ease of drawing, only one blade 50 is shown, and the other two are omitted. The three blades 50 are shown in Figure 5(a) described below.

[0023] The number of blades 50 is arbitrary. With one blade, it is difficult to obtain stable turning. With two blades, although there is an improvement over one blade, some imbalance during turning remains. With three blades 50 arranged at a circumferential pitch of 120°, balance during turning is improved. With four blades, the blades 50 are arranged at a circumferential pitch of 90°, and balance during turning is improved. Therefore, although the number of blades 50 is arbitrary, three (or four or more) is recommended.

[0024] Although not essential, it is preferable to add an arm 24 extending from the base 11, a float holder 25 attached to the end of the arm 24, a float 26, and a retaining ring 27.

[0025] [Geared motor] The geared motor 13 is a structure in which a geared reducer and an electric motor are integrated. The reduction ratio of the geared reducer is approximately 1:400. The rated rotational speed of the electric motor is approximately 1,500 revolutions per minute. Specifically, the input shaft of the geared reducer is a hollow shaft. The motor shaft of the electric motor is fitted into this hollow shaft.

[0026] Although it is possible to fit a drive pulley onto the motor shaft, fit a driven pulley onto the input shaft of the gear reducer, and stretch a timing belt between the drive pulley and the driven pulley, adopting a motor 13 with a reducer has the advantage of eliminating the drive pulley, driven pulley, and timing belt.

[0027] Furthermore, when a drive pulley, driven pulley, and timing belt are present, a waterproof cover is required to waterproof them, and this waterproof cover becomes large and complex in structure. In this regard, the motor with a speed reducer 13 allows the motor and the speed reducer to be housed in a single housing. By providing waterproof performance to the housing, the waterproof cover can be omitted. The motor with a speed reducer 13 has the advantage that even if a waterproof cover is provided, this waterproof cover can be small and simple in structure. Therefore, the motor with a speed reducer 13 is suitable for the water purifier 100 of the present invention, which is used outdoors and floats on the water surface.

[0028] The reducer-equipped motor 13 can be a geared motor. A geared motor is equipped with a gear-type reducer, and the gears of this gear-type reducer are composed of spur gears or helical gears. The reducer-equipped motor 13 may also be a motor with a planetary gear reducer. A planetary gear reducer motor is equipped with a gear-type reducer, and the gears of this gear-type reducer are composed of planetary gears. The reducer-equipped motor 13 may also be a motor with a cycloidal / trochoidal reducer. A cycloidal / trochoidal reducer motor is equipped with a gear-type reducer, and this gear-type reducer is composed of a cycloidal / trochoidal reducer.

[0029] In a geared motor, the motor shaft and the reducer output shaft are misaligned in the direction perpendicular to the axis. Therefore, balance adjustment is required when the motor is installed vertically. In contrast, a motor with a planetary gear reducer and a motor with a cycloidal / trochoidal reducer are preferable because the motor shaft and the reducer output shaft are coaxially arranged and are symmetrical about the vertical axis, eliminating (or facilitating) balance adjustment. However, geared motors have the advantage of being less expensive than motors with planetary gear reducers and motors with cycloidal / trochoidal reducers. Therefore, the selection of the reducer motor 13 can be made as appropriate.

[0030] [Materials of Elements] The base 11, the boss plate 22, the Y-shaped housing upper part 15, and the Y-shaped housing lower part 16 are preferably made of stainless steel, which is strong and water-resistant. The float 17 is preferably made of foamed resin, particularly polystyrene foam (foamed styrene). The rod 18 and the blades 50 are preferably made of polyvinyl chloride, which is lightweight and water-resistant. However, the materials of each element may be changed or selected as appropriate.

[0031] [Assembly of Elements] The above-described components can be assembled in any manner, and one example will be described below. In the following description, the bolt is placed on top and the nut on the bottom, but the nut may also be placed on top and the bolt on the bottom. Also, although not described in the following description, a flat washer and a spring washer are interposed between the bolt and the nut.

[0032] The float 17 is placed on the lower housing part 16. The upper housing part 15 is placed over this float 17. The upper housing part 15 is connected to the lower housing part 16 with a first bolt 31 and a nut 32. As a result, the float housing 14 consisting of the upper housing part 15 and the lower housing part 16 is completed. Because the float housing 14 is disassembled, if the float 17 becomes damaged, it can be easily replaced with a new float 17.

[0033] The reducer-equipped motor 13 is placed on the base 11, and the second bolt 33 is screwed into the reducer-equipped motor 13, thereby joining the reducer-equipped motor 13 to the base 11. Next, the boss 21 is fitted onto the rotating shaft 12, which is the output shaft of the reducer-equipped motor 13, and the set screw 34 is tightened. This integrates the base 11, reducer-equipped motor 13, and boss-equipped plate 22.

[0034] A third bolt 35 is pre-welded to the housing upper part 15 with the tip of the bolt convex upward. Then, the bossed plate 22 is placed on the housing upper part 15, and a nut 36 is screwed onto the third bolt 35, thereby fixing the bossed plate 22 to the housing upper part 15. In this way, the base 11, the motor with speed reducer 13, the bossed plate 22, the float housing 14, and the float 17 are integrated.

[0035] Next, the rod 18 is fixed to the lower housing part 16 with a fourth bolt 37 and a nut 38. At an appropriate timing, the arm 24 is fixed to the base 11 with a fifth bolt 41 and a nut 42, the float holder 25 is fixed to the arm 24 with a sixth bolt 43 and a nut 44, the float 26 is fitted into the float holder 25, and the retaining ring 27 is attached.

[0036] As shown in Figure 3(a), the blade 50 is attached to the tip of the rod 18. Preferably, a plate 60, a reinforcing plate 61, and a reinforcing angle 62 are added to the tip of the rod 18.

[0037] 3(b), the blade 50 is fixed by welding to the rod 18. The blade 50 is made up of an upper flange 54, a lower flange 55 and a web 56 connecting these together, and is a channel that opens forward in the traveling direction.

[0038] Preferably, a plate 60 is attached to the lower flange 55. The front-to-rear width of this plate 60 in the direction of travel is defined as Wp. The width Wp of the plate 60 is set to 6 to 12 times, preferably 8 to 10 times, the width Wf of the lower flange 55. To prevent the plate 60 from swinging up and down, a reinforcing plate 61 is hung from the rod 18, and further reinforced with a reinforcing angle 62.

[0039] [Water Purification Device] After assembling the above elements, the water purification device 10 is as shown in Figure 4. As shown in Figure 4, the float 17 allows the water purification device 10 to float on the water surface 64. At this time, the water surface 64 and the upper flange 54 of the blade 50 are flush with each other (including being substantially flush with each other).

[0040] The base 11 is pulled by a wire (see FIG. 5, reference numeral 19) and does not rotate around the rotating shaft 12. Therefore, when the motor 13 with a reducer is put into operation, the rotating shaft 12 rotates at a predetermined rotation speed (3 to 6 rotations per minute), and this rotating shaft 12 rotates the float housing 14 and the float 17, causing the rod 18 and the blade 50 to turn.

[0041] The water purification device 10 described above can be installed in any body of water with very little or no current, such as a large aquarium, pond, marsh, lake, estuary, or inlet. A specific example of installation in a pond will be described below.

[0042] [Pond] Fig. 5(a) shows only a portion of a pond 65 for ease of drawing. As shown in Fig. 5(b), wire stoppers 66 are provided on the edge of the pond 65. Then, as shown in Fig. 5(a), the water purification device 10 according to the present invention is floated on the pond 65, and wires 19 are stretched between the base 11 and the wire stoppers 66. The number of wires 19 can be any number, but three is preferable.

[0043] One of the wires is connected to the tip of an arm 24, not to the base 11. The arm 24 acts to prevent the base 11 from rotating. The arm 24 also has a float 26 at its tip. Therefore, the arm 24 also serves to prevent the water purification device 10 from rolling.

[0044] After the water purification device 10 has been operated for a certain period of time, the length of the wire 19 is changed. When the length of the wire 19 is changed, the position of the water purification device 10 is changed. By repeatedly changing the position, the large pond 65 can be purified evenly.

[0045] Alternatively, the wire 19 may be removed and an anchor attached to the float 26. The anchor will fix the position of the float 26. The water purification device 10 will float around the float 26. This drifting allows the pond 65 to be purified more evenly.

[0046] 5(a), the wire 19 may be removed, three arms 24 may be extended from the base 11 at 120° intervals, and a float 26 may be attached to each end of the arms 24. Therefore, it is possible to select any of the following usage modes: fixing the position of the water purification device 10 by pulling with the wire 19, rotating the water purification device 10 without the wire 19, or floating the water purification device 10 without the wire 19.

[0047] [Operation of the Water Purification Apparatus] The operation of the water purification apparatus 10 according to the present invention has been briefly described above with reference to FIG. 1(b), but the operation of the water purification apparatus 10 will now be described in detail with reference to other drawings.

[0048] [First Action] In Figure 6(c), the region Wc between the housing upper part 15 and the blades 50 is substantially open in the vertical direction, with only the elongated rod 18 existing therein. Therefore, the upward flow (arrow (82)) is not impeded but is encouraged. That is, due to the first action, the upward flow (arrow (82)) is not impeded but is encouraged.

[0049] [Second Action] As shown in Figure 6(a), the blade 50 rotates as indicated by the white arrow. As shown in Figure 6(b), the upper flange 54 of the blade 50 is aligned (or almost aligned) with the water surface 64, and the lower flange 55 is submerged in water. When the blade 50 pushes against the water, the water tries to move up and down and left and right (front and back directions in the drawing) parallel to the web 56. However, the upper flange 54 restricts the water's upward movement, and the lower flange 55 restricts the water's downward movement. Therefore, the channel-shaped blade 50 plays a role in grabbing water and preventing it from escaping. That is, the second action is for the blade 50 to grab water.

[0050] Because water is prevented from escaping above or below the blade 50, in Figure 6(c) water actively escapes from the outer end 51 and inner end 52 of the blade 50. Note the water escaping from the inner end 52. This water passes through the area Wc formed between the blade 50 and the float housing 14, and apparently escapes away from the surface of the drawing. Therefore, area Wc becomes a water passage 53. As if induced by this escape, the upward flow (arrow (82)) becomes even stronger. In other words, the synergistic action of the first and second effects further strengthens the upward flow (arrow (82)).

[0051] [Third Action] The first and second actions described above can be achieved even without the plate 60 shown in FIG. 6(b). However, since the plate 60 achieves the third action described below, it is recommended to provide the plate 60. In FIG. 6(b), the area above the plate 60 momentarily becomes a water-free space 67. Then, when the plate 60 moves as shown by the white arrow, the original water-free space 67 is filled with water. The water below the plate 60 moves upward by the amount of water that fills the water-free space 67. This movement is called the third action.

[0052] However, this phenomenon is difficult to achieve if the water around the plate 60 is turbulent. Therefore, the plate 60 is placed parallel to the water surface 64. When placed parallel, the plate 60 acts similarly to a fish's fin and does not turbulence the water. As a result, the third effect is obtained. In other words, the third effect is strengthened by not disturbing the water at the surface.

[0053] Furthermore, the larger the waterless space 67, the stronger the third effect. Because the size of the waterless space 67 is proportional to the width Wp of the plate 60, the width Wp of the plate 60 is set to at least six times the width Wf of the lower flange 55. If it is six times or more, a sufficiently large third effect can be obtained. However, if it exceeds 12 times, it becomes difficult to maintain the rigidity of the plate 60, and the tip of the plate 60 will swing up and down, disturbing the water. For these reasons, the width Wp of the plate 60 is set in the range of 6 to 12 times the width Wf of the lower flange 55.

[0054] [Modifications of the Blades] The mounting configuration of the blades 50 explained in Fig. 3(b) can be modified. Modifications will be explained with reference to Figs. 7(a) to 7(g).

[0055] As shown in Figure 7(a), the channel-shaped blade 50 may be attached to a rod 18 made of a round tube, and a triangular bracket 69 may be placed between the blade 50 and the rod 18. Alternatively, as shown in Figure 7(b), the channel-shaped blade 50 may be attached to a rod 18 made of a square tube, and a triangular bracket 69 may be placed between the blade 50 and the rod 18.

[0056] The structure shown in Figure 7(a) or 7(b) does not achieve the third function described above, but does achieve the first and second functions. The structures shown in Figures 7(a) and 7(b) do not include the plate 60 and reinforcing plate 61 shown in Figure 3(b), and therefore have the advantage of being simple and inexpensive.

[0057] As shown in Figure 7(c), an inverted L-shaped blade 50 may be attached to a rod 18 made of a round tube, with a triangular bracket 69 spanning the blade 50 and the rod 18. An upper flange 54 can prevent water from escaping upward. As shown in Figure 7(d), an inverted L-shaped blade 50 may be attached to a rod 18 made of a square tube, with a triangular bracket 69 spanning the blade 50 and the rod 18. An upper flange 54 can prevent water from escaping upward.

[0058] The structure shown in Figure 7(c) or 7(d) does not achieve the second and third functions described above, but does achieve the first function. The structures shown in Figures 7(c) and 7(d) do not include the bottom flange 55 shown in Figures 7(a) and 7(b), and therefore have the advantage of being simpler and less expensive.

[0059] 7(e), an I-shaped blade 50 may be attached to a rod 18 made of a round tube, with a triangular bracket 69 spanning between the blade 50 and the rod 18. Also, as shown in FIG. 7(f), an I-shaped blade 50 may be attached to a rod 18 made of a square tube, with a triangular bracket 69 spanning between the blade 50 and the rod 18.

[0060] The structure shown in Figure 7(e) or 7(f) does not achieve the second and third functions described above, but does achieve the first function. The structures shown in Figures 7(e) and 7(f) do not include the upper flange 54 shown in Figures 7(c) and 7(d), and therefore have the advantage of being simpler and less expensive.

[0061] Alternatively, as shown in Figure 7(g), channel-shaped blades 50 may be attached to a rod 18 made of a square tube, a plate 60 may be extended from the bottom of the blades 50, and a triangular bracket 69 may be placed between this plate 60 and the rod 18. The structure shown in Figure 7(g) achieves all of the first to third functions described above. The structure shown in Figure 7(g) also has the advantage that the reinforcing plate 61 shown in Figure 3(b) is unnecessary and the reinforcing angle 62 can be replaced with a simpler triangular bracket 69.

[0062] However, although square pipes have the advantage of being easier to attach the blades 50 to than round pipes, they have the disadvantage of being less available on the market than round pipes, being somewhat more difficult to obtain, and being more expensive. Taking into account the advantages and disadvantages, it is possible to select whether to use a round pipe or a square pipe for the rod 18. Therefore, the rod 18 is not limited to a round pipe.

[0063] Based on the above explanation, the present invention can be summarized as follows: As shown in Figure 4, a water purification device 10 rotates blades 50 extending radially from a rotating shaft 12 standing perpendicular to the water surface 64, floating on the water surface 64, and purifies water by raising rivers flowing radially from the center of rotation of the blades 50 onto the water surface without splashing up the water on the water surface 64, the water purification device 10 comprising a float 17 disposed below the rotating shaft 12, a float housing 14 surrounding the float 17 and rotated by the rotating shaft 12, a rod 18 extending radially from the float housing 14, and the blades 50 attached to the rod 18, and a water passage 53 for carrying water pushed by the blades 50 is provided between the blades 50 and the float housing 14.

[0064] In this case, the blades 50 may be attached in either the form shown in FIG. 3(b) or the form shown in FIGS. 7(a) to 7(g).

[0065] Preferably, as shown in Figure 6 (b), the blade 50 is a channel consisting of an upper flange 54, a lower flange 55, and a web 56 connecting them, which opens forward in the direction of travel, with the upper flange 54 positioned on the water surface 64 and the lower flange 55 positioned underwater, and the upper flange 54 and the lower flange 55 acting to grab the water on the water surface 64.

[0066] The upper flange 54 prevents water from escaping upward, and the lower flange 55 prevents water from escaping downward. In this case, the blades 50 may be attached in any of the forms shown in Figure 3(b) or Figures 7(a), 7(b), and 7(g).

[0067] Preferably, as shown in FIG. 6( b ), the lower flange 55 includes a plate 60 that extends rearward in the traveling direction along the water surface 64 .

[0068] The plate 60 extends along the water surface 64, and therefore moves under the water without disturbing the water below. In this case, the blades 50 may be attached in either the form shown in Fig. 3(b) or the form shown in Fig. 7(g).

[0069] The configuration (structure) of the water purification device 10 according to the present invention is not limited to the embodiment, and may be modified as appropriate as long as the functions and effects of the present invention are achieved.

[0070] The present invention is suitable for use in a water purification device for purifying water in large aquariums, ponds, marshes, lakes, estuaries, inlets, and the like.

[0071] 10...water purification device, 11...base, 12...rotating shaft, 13...motor with reducer, 14...float housing, 15...upper housing, 16...lower housing, 17...float, 18...rod, 19...wire, 50...vane, 51...outer end, 52...inner end, 53...water passage, 54...upper flange, 55...lower flange, 56...web, 60...plate, 61...reinforcing plate, 62...reinforcing angle, 64...water surface, 65...pond, Wf...width of lower flange, Wp...width of plate.

Claims

1. A water purification device that purifies water by rotating blades that extend radially from a rotating shaft that is set up perpendicular to the water surface, floating on the surface of the water, and raising a river that flows radially from the center of rotation of the blades to the surface of the water without splashing up the water on the surface, the water purification device comprising: a float placed below the rotating shaft; a float housing that surrounds the float and is rotated by the rotating shaft; a rod that extends radially from the float housing; and the blades attached to the rod, and a water passage that carries water pushed by the blades is provided between the blades and the floating housing.

2. A water purification device as described in claim 1, wherein the blades are channels consisting of an upper flange, a lower flange and a web connecting them, which open forward in the direction of travel, the upper flange being placed on the water surface and the lower flange being placed underwater, and the upper flange and the lower flange acting to grab water on the surface of the water.

3. A water purification device according to claim 2, wherein the lower flange is provided with a plate extending rearward in the direction of travel along the water surface.

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