EP0465908A1

EP0465908A1 - Water drawing and guiding device for jet-propelled gliding boats

Info

Publication number: EP0465908A1
Application number: EP91110377A
Authority: EP
Inventors: Yukio Nakamura
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-07-10
Filing date: 1991-06-24
Publication date: 1992-01-15
Also published as: JPH0471993A; AU7920291A; CA2044349A1

Abstract

The present invention relates to a water drawing and guiding device for jet-propelled gliding boats, wherein a scope gate for preventing entry of floating obstacles is attached to a water intake port formed in the bottom surface of the boat body, and

the water drawn from the water intake port is accelerated by an impeller housed in a water intake duct and spouted rearwardly of the boat body, the water drawing and guiding device being characterized in that:
the scope gate is made of elastic transparent or translucent engineering plastic material into the form of a longitudinally elongated rectangle having a pair of attaching seats and a pair of flow regulating vertical walls,
the arrangement being such that during the turning of the boat body, the flow regulating vertical walls flex to and fro like plate springs, the main object thereof being to provide an extremely smooth reliable water drawing action without excessively holding back natural water flow moving from the water intake port to the water intake duct or without agitating water to the extent of bubbling or decreasing the flow rate of water, thereby preventing cavitation from taking place in the water intake duct.

Description

BACKGROUND OF THE INVENTION

Small-sized gliding boats of the jet-propelled type arranged for a single person to ride in a standing posture or some persons to ride in a seated posture have incorporated therein a jet-propelling device (or water jet pump) adapted to be driven for rotation by an engine mounted on the boat.
Such jet propelling device is designed to draw water through a water intake port formed in the bottom surface of the boat body, accelerating said water by an impeller installed in a water intake duct (or pump case) to spout it rearwardly of the boat body, the reaction force serving as the propelling force for the boat body. Thus, the jet propelling device has the danger of drawing not only water but also garbage, seaweed, fishing lines and other various floating obstacles. Therefore, to prevent entry of such obstacles, a special lattice called scope gate or grate is attached to the bottom surface of the boat body to cover said water intake port.
The scope gate which has heretofore been most popular, as shown in Figs. 12 and 13, is in the form of an elongated rectangle comprising a pair of front and rear attaching seats 1 and 2 and a pair of side bars 3 and 4, said lattice having one or more partition bars 5 projecting parallel with said side bars 3 and 4. At any rate, the whole structure is usually made by casting of aluminum alloy or other light metal. The side bars 3 and 4 and partition bar 5 are shown circular in cross section in these figures, but bars having vertically elongated elliptical and rectangular cross sections are also known.
Such scope gate is removably or exchangeably attached to the bottom surface of the boat body to cover the water intake port while projecting somewhat downward. In the attached state, the side bars 3 and 4 and partition bar 5 extend parallel with the travel center line of the boat body, so that, coupled with the high rigidity of the metal product, they add to the straight-travel stability during gliding of the boat body.
Since it is attached to the bottom surface of the boat body in such a manner as to project somewhat downward, even if the boat body runs on shallows or on drifting wood, the bottom surface will not hit the same; thus, the scope gate serves to prevent the boat body from being damaged. Furthermore, during the turning of the boat body, it provides the boat body with a sideslip preventing effect (so-called edging effect) with said side bars 3 and 4 and partition bar 5 serving as fins, and it also increases the rate of flow of water into said water intake port.
Further, another advantage is that the larger the number of partition bars, the greater the effect of preventing entry of obstacles.
However, such advantages will not necessarily manifest themselves during the turning of the boat body. The reason is that the scope gate is made of metal.
More particularly, first, if the conventional scope gate projects too much downward from the bottom surface of the boat body, the sideslip preventing effect of the side bars 3 and 4 and partition bar 5 on the boat body will be excessively high owing to the high rigidity of the metal product, resulting in a high resistance to the turning of the boat body to make it difficult to attain smooth steering of the boat body. For beginners, such conventional scope gate even has the danger of rolling the boat body sideways.
On the contrary, if it does not at all project downward from the bottom surface of the boat body, the aforesaid advantages cannot be obtained. Rich experience is required in determining the moderate amount of projection. It seems that a scope gate equipped with a projection adjusting mechanism has not been commercially available.
Secondly, even if the rate of flow of water into the water intake port can be increased by attaching the scope gate to the bottom surface of the boat body in such a manner as to project downward therefrom, the high rigidity of the metal product causes the side bars 3 and 4 and partition bar 5 to excessively hold back the natural flow of water moving from the water intake port to the water intake duct, or the water dashes against them and is thereby agitated, bubbling and disturbed.
As a result, cavitation takes place in the water intake duct (or pump case), corroding the impeller or causing energy loss. It is clear that the larger the number of said partition bars 5, the more noticeable are such problems.
Thirdly, since the conventional scope gate is a metal product, it forms an obstacle to visual inspection of the interior of the water intake duct through the water intake port of the boat body. For example, if a floating obstacle enters the water intake duct and twines itself around the impeller, impeller shaft or the like, the twining state cannot be visually inspected unless the boat body is turned upside down to bring its bottom surface into view, and this operation of turning upside down requires hard labor. And the larger the number of partition bars 5, the more remarkable is such problem.
Fourthly, essentially such scope gate is used by being removably or exchangeably attached to the bottom surface of the boat body in accordance with the user's taste, steering skill and experience. And the attaching bolts tend to loosen owing to vibrations or chocks produced in the boat body during the gliding of the boat body. Not infrequently, it is only after the user has landed that he finds that the scope gate is missing.
Therefore, in practice, a silicone type binder is applied to the scope gate attaching bolts despite the fact that the scope gate is intended to be removably attached to the boat body. If the scope gate should be missing, since the conventional scope gate is a metal product, it sinks into depths never to be found, thus polluting the sea and lakes.

SUMMARY OF THE INVENTION

The present invention has been proposed to solve these problems.
First, an object of the invention is to provide an arrangement wherein the scope gate is made of polycarbonate resin or other engineering plastic material having high bending rigidity, said scope gate being in the form of an elongated rectangle having a pair of attaching seats and a pair of flow regulating vertical walls, said flow regulating vertical walls being adapted to be laterally flexed like plate springs during the turning of the boat body; therefore, even if it is attached to the boat body to project downward from the bottom surface of the boat body, it does not give the boat body an excessively high sideslip preventing effect, so that even a beginner can steer the boat body for turning safely and smoothly while assuring smooth reliable water drawing action without holding back the natural flow of water moving from the water intake port to the water intake duct or without undesirably agitating water or decreasing the flow rate of water, thereby preventing cavitation from taking place in the water intake duct.
Particularly, if the cross-sections of the flow regulating vertical walls capable of deforming like plate springs are shaped symmetrical and in the form of a basic triangle or trapezoid with its thickness gradually decreasing upward, it follows that if the boat body is tilted during turning, since the upwardly tapered surfaces of the flow regulating vertical walls are flexed into substantially parallel relation to the water surface, the object of smoothing the flow of water moving from the water intake port to the water intake duct can be rationally attained.
Secondly, an object of the invention is to provide an arrangement wherein a partition flow regulating vertical wall is installed parallel with and between said flow regulating vertical walls, said partition flow regulating vertical wall having a substantially isosceles triangular cross-section with its thickness gradually decreasing upward, whereby the scope gate is internally partitioned to make it difficult for floating obstacles to enter and the water drawing action during the turning of the boat body is smoothed.
Thirdly, an object of the invention is to provide an arrangement wherein the lower surface regions of the flow regulating vertical walls are substantially V-shaped as seen laterally of the boat body with their lower edges projecting gradually downward starting with the opposite sides toward the middle, whereby, despite the fact that the scope gate itself is a plastic product allowing the flow regulating vertical walls to flex, the intermediate regions of the flow regulating vertical walls farthest from the pair of opposed seats are physically structurally reinforced to increase the durability of the scope gate.
Fourthly, an object of the invention is to provide an arrangement wherein the scope gate is made of transparent or translucent plastic material so that it can be seen through; thus, the interior of the water intake duct can be reliably visually inspected from the water intake port without having to turn the boat body upside down to bring its bottom surface into view.
This object can also be attained even if said partition flow regulating vertical wall is added, so long as it is also transparent or translucent.
Fifthly, an object of the invention is to provide an arrangement wherein the scope gate, which is a molding of plastic material, is colored with a coloring agent, particularly with a fluorescent material, so that if an accident should happen in the offing to make the boat body incapable of traveling, the coloration facilltates search for the boat body. Further, since the scope gate is a plastic product, it floats on water, a fact which also facilitates search if it should be missing.
Sixthly, an object of the invention is to provide an arrangement wherein the open edges of the pair of attaching seats opposed to the interior of the lattice of the scope gate are formed as slope surfaces rearwardly ascending at given angles, whereby water is introduced into the water intake port with much less resistance during travel of the boat body.
Other objects as well as the arrangement of the invention will become apparent from the following detailed description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic side view of a jet-propelled gliding boat with the present invention applied thereto;
Fig. 2 is an enlarged bottom view showing the rear portion of the boat body;
Fig. 3 is a sectional view taken along the line 3-3 in Fig. 2;
Fig. 4 is a perspective view of a scope gate;
Fig. 5 is a sectional view taken along the line 5-5 in Fig. 4;
Fig. 6 is an enlarged sectional view taken along the line 6-6 in Fig. 4;
Figs. 7 and 8 are front sectional views showing two modifications corresponding to Fig. 6;
Fig. 9 is a front sectional view for explaining flexure produced in the scope gate during the turning of the boat body;
Fig. 10 is a perspective view showing a modification of a scope gate corresponding to Fig. 4;
Fig. 11 is an enlarged sectional view taken along the line 11-11 in fig. 10;
Fig. 12 is a perspective view showing a conventional scope gate; and
Fig. 13 is an enlarged sectional view taken along the line 13-13 in Fig. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The concrete arrangement of the invention will now be described in detail with reference to the drawings. In Fig. 1 schematically showing a jet-propelled small-sized gliding boat in its entirety, the character A generally denotes a boat body made of fiber-reinforced plastic (FRP), said boat body being of hollow sealed construction including a front region defined as an engine room 10 and a rear region with its upper surface defined as a floor deck 11 for a driver to ride in a standing posture. In some cases, the middle area of the floor deck 11 will be provided with a seat for a driver. The numeral 12 denotes an engine contained in the engine room 10 for driving a jet-propelling device (water jet pump) B through a propeller shaft 13 to impart a propelling force to the boat body A.
The propeller shaft 13 extends along the travel center line of the boat body A to a position below the floor deck 11 and is connected at its front end to the crank shaft (not shown) of the engine 12 through a clutch 14. Integrally rotatably connected to the rear end of the propeller shaft 13 are an impeller 15 and guide vanes 16. The numeral 17 denotes a water intake duct serving as a pump case for receiving the impeller 15 and guide vanes 16, said water intake duct being disposed below the floor deck 11, with its front side providing a water intake port 18 which opens in the middle of the bottom surface of the boat body A.
When the impeller shaft 13 is driven for rotation, its impeller 15 draws water through the water intake port 18. In the water intake duct 17, the water drawn is accelerated and forced rearward by the impeller 15 and its flow is regulated by the guide vanes 16, thereupon it is spouted out through a steering nozzle 19 which opens in the stern of the boat body A; the reaction to the spouting force advances the boat body A.
The steering nozzle 19 is manually controlled from the floor deck 11 to change its direction, whereby the boat body A can be steered. In addition, the numeral 20 denotes a pump case cover attached to the middle region of the bottom surface of the boat body A.
Since there is a danger of garbage, seaweed, fishing lines and other various floating obstacles being drawn in together with water through the water intake port 18, a scope gate C for preventing entry thereof is attached to the middle region of the bottom surface of the boat body A to cover the water intake port 18, as shown in Figs. 2 and 3. In the present invention, the scope gate C is made by injection molding of a polycarbonate resin (preferably, one marketed under the trade name of Taflon, from Idemitu Petroleum Chemistry Co., Ltd.) having high bending rigidity (desirably, about 23,000 kg/cm² or above), polyacetal resin or other thermoplastic engineering plastic material into the form of an elongated rectangle, as shown in Figs. 4 through 6, the entire molding being transparent.
In Figs. 4 through 6 showing the scope gate C, the numerals 21 and 22 denote a pair of attaching seats having a width w smaller than the width s of said water intake port 18. The front attaching seat 21 has a pair of bolt receiving holes 23 on opposite sides, while the rear attaching seat 22 is centrally formed with a bolt receiving hole 24 which desirably is elongated in the longitudinal direction. The number and disposition of bolt receiving holes 23, 24 may be freely changed in connection with the boat body A.
The attaching seats 21 and 22 are applied at their flat surfaces to the bottom surface of the boat body A and then fixed thereto by stud bolts 25 and 26 so that the scope gate C can be removed or exchanged.
The open edges of the attaching seats 21 and 22 of the scope gate C opposed to the interior of the lattice are formed as slope surfaces 21 a and 22a rearwardly ascending at given angles a and with respect to the horizontal surface. Thus, water can be smoothly drawn from the water intake port 18 of the boat body A into the water intake duct without disturbing water.
The numerals 27 and 28 denote a pair of flow regulating vertical walls spanning the space between the attaching seat 21 and 22 and extending across the water intake port 18 of the boat body A with the lateral surfaces thereof being approximately orthogonal to the attaching surfaces of said seats.
Thus, coupled with the fact that the scope gate C itself is made of said plastic material, this arrangement ensures that during the turning of the boat body A, the urging force of water is supported by the upright surfaces of the flow regulating vertical walls 27 and 28, which then flex to and fro as shown in chain lines in Fig. 9 as if they were plate springs. This flexure of the flow regulating vertical walls 27 and 28 allows water to flow without excessively holding back or disturbing the same; thus, water is smoothly drawn in through the water intake port 18 of the boat body A.
In addition, when the boat body A is traveling straight with the upright lateral surfaces receiving no pressure of water laterally of the boat body A, the flow regulating vertical walls 27 and 28 are, of course, restored to the original state.
Further, the cross-sections of the flow regulating vertical walls 27 and 28 are shaped symmetrical and in the form of a basic triangle or trapezoid with its thickness gradually decreasing upward, as shown in Fig. 6. That is, the lateral surfaces of the flow regulating vertical walls 27 and 28 are slope surfaces 27a, 27b and 28a, 28b with the thickness gradually decreasing upward at angles of y and 0.
As a result, water can be extremely smoothly drawn into the water intake port 18 as it is guided to the travel center line of the boat body A. Further, even if the boat body A is tilted during turning, the flow regulating vertical walls of the scope gate C integral therewith are also tilted such that their upright lateral surfaces are orthogonal to the water surface as suggested in Fig. 9. Therefore, holding back and disturbance of water are suppressed, and substantially the same amount of water as during straight travel is smoothly drawn from the water intake port 18 into the water intake duct 17.
For this reason, the cross-sections of the flow regulating vertical walls 27 and 28 should, most effectively, be in the shape of an isosceles trapezoid shown in Fig. 6, or a modification thereof such as an ellipse, an oval or a waterdrop, as shown in Fig. 7. However, so long as the symmetrical cross-sections of the flow regulating vertical walls 27 and 28 are maintained, the cross-sections may be in the form of a non-isosceles trapezoid, as shown in Fig. 8, or a right triangle.
When the flow regulating vertical walls 27 and 28 are seen laterally of the boat body A, as is clear from Figs. 3 through 5, their upper surfaces are horizontal, whereas their lower surfaces are V-shaped gradually downwardly projecting as the approximately intermediate region is reached.
That is, the lower surfaces of the approximately front halves of the flow regulating vertical walls 27 and 28 are forwardly upward slope surface 27c and 28c connected flush to the lower surface of the front attaching seat 21, while the lower surfaces of the remaining rear halves are rearwardly upward slope surface 27d and 28d connected flush to the lower surface of the rear attaching seat 22; thus, the approximately middle region where the slope surfaces 27c, 28c, 27d, 28d cross each other projects downward by the greatest amount. The character denotes the crossing angle between the forwardly and rearwardly upward slope surfaces 27c, 28c, 27d, 28d.
Thus, the scope gate C itself is integrally made of said plastic material to enable the flow regulating vertical walls 27 and 28 to flex during turning movement, while the intermediate region between the flow regulating vertical walls 27 and 28 remotest from the attaching seats 21 and 22 can be strengthened to be free from the danger of being physically broken. Further, the front halves of the flow regulating vertical walls 27 and 28 have their lower surfaces designed to define forwardly slope surfaces 27c and 28c; therefore, the boat body A can be given lift by water acting on said surfaces during travel of the boat body A.
Figs. 10 and 11 show a modification of a scope gate corresponding to Figs. 4 through 6, and the relation to Figs. 4 through 6 is indicated by multiplying the numbers by 10. In this modification, a partition flow regulating vertical wall 290 is interposed between the flow regulating vertical walls 270 and 280 in parallel relation to the latter, thereby enhancing the effect of preventing entry of floating obstacles. The cross-sectional shape of the partition flow regulating vertical wall 290 is determined in positional relation to the flow regulating vertical walls 270 and 280; thus, it is an isosceles trapezoid or an isosceles triangle, as shown in Fig. 11, or it is a modification of said figure, such as an ellipse or a waterdrop shape. In addition, the partition flow regulating vertical wall 290 may be increased in number to two or more so long as they extend parallel with the flow regulating vertical walls 270 and 280.
At any rate, in attaching the scope gate C to the bottom surface of the boat body A, it is effective, as is suggested in Fig. 3, to position it such that the rear halves of the flow regulating vertical walls 27 and 28 project downward beyond the bottom surface of the boat body A by a given amount h.
Thereby, floating obstacles tending to adhere to the rear end of the water intake port 18 formed in the bottom surface of the boat body A are quickly guided rearward by the rear halves of the flow regulating vertical walls 27 and 28 projecting downward beyond the bottom surface of the boat body A. Further, when the boat body A is turning, the rear halves of the flow regulating vertical walls 27 and 28 exhibit the effect of preventing sideslip of the boat body A. However, in that case, since the flow regulating vertical walls 27 and 28 themselves will flex to and fro, as described above, there is no danger of the sideslip preventing effect being too high.
It has been stated that the scope gate C is molded of transparent or translucent plastic material, in addition to this transparency, it is desirable to apply a suitable fluorescent coloring agent. Then, even if an accident which makes it impossible for the boat body A to glide should happen, the boat body can be easily searched for with the color as a guide.
As described above, the scope gate C of the present invention is integrally molded of transparent or translucent engineering plastic material into the form of an elongated lattice, and a pair of longitudinally extending flow regulating vertical walls 27 and 28 are adapted to flex to and fro during the turning of the boat body A. Thus, water can be drawn very smoothly without the danger of excessively holding back or disturbing the flow of water moving from the water intake port 18 to the water intake duct 17 or the danger of decreasing the flow rate of water. Nor is the danger of causing cavitation in the water intake duct 17.
Further, since the scope gate C can be seen through, the interior of the water intake duct 17 can be inspected by simply glancing at the water intake port 18 without having to turn the boat body A over to bring its bottom surface into view. Such effect will not be lost even if the partition flow regulating vertical wall 290 is interposed to partition the lattice, and the efficiency of inspection and maintenance is high.
Particularly, if the cross-sections of the flow regulating vertical walls 27 and 28 are made symmetrical and in the form of a basic triangle or trapezoid with its thickness gradually decreasing upward, then water can be extremely smoothly drawn into the water intake port 18 along the travel center line during straight travel of the boat body A. Further, if the boat body A is tilted during its turning, the upwardly converging slope surfaces 27a, 27b and 28a, 28b of the flow regulating vertical walls 27 and 28 are caused to be orthogonal to the water surface. This, coupled with said flexure, causes the same amount of water as during straight travel to flow into the water intake port 18 while more smoothly regulating the flow without the danger of the flow regulating vertical walls 27 and 28 holding back or disturbing water.
If the bottom surfaces of the flow regulating vertical walls 27 and 28 are V-shaped, as seen laterally of the boat body A, gradually downwardly projecting as the approximately intermediate regions are reached, then the approximately intermediate regions of the flow regulating vertical walls 27 and 28 remotest from the pair of attaching seats 21 and 22 can be physically reinforced to be free from damage thereto while making the scope gate C itself in the form of a plastic article to allow the flow regulating vertical walls 27 and 28 to flex; thus, the durability is enhanced.
Further, if a partition flow regulating vertical wall 290 is interposed between the flow regulating vertical walls 270 and 280 in parallel relation to the latter and its cross-section is in the form of an isosceles triangle or an isosceles trapezoid with its thickness gradually decreasing upward, then since the interior of the lattice of the scope gate C is partitioned by the partition flow regulating vertical wall 290, the entry of floating obstacles into the water intake port 18 can be prevented more reliably while said flexure is being exhibited during the turning of the boat body A.
If the open edges of the attaching seats 21 and 22 of the scope gate C opposed to the interior of the lattice are formed as slope surfaces 21 a and 22a rearwardly ascending at given angles a and ;8, then water can be introduced more smoothly into the water intake port 18 by the rearwardly ascending slope surfaces 21 a and 22a of the attaching seats 21 and 22.
Further, if the entire scope gate C is colored preferably with a fluorescent coloring agent, the boat body A can be given an external appearance which is harmonious with the boat body C. Thus, if an accident which makes gliding impossible or an accident of coming off of the scope gate C should happen in the offing, the search thereof is facilitated.

Claims

1. A water drawing and guiding device for jet-propelled gliding boats, wherein a scope gate for preventing entry of floating obstacles is attached to a water intake port formed in the bottom surface of the boat body, and

the water drawn from the water intake port is accelerated by an impeller housed in a water intake duct and spouted rearwardly of the boat body,

said water drawing and guiding device being characterized in that:

said scope gate is made of elastic transparent or translucent engineering plastic material into the form of a longitudinally elongated rectangle having a pair of attaching seats and a pair of flow regulating vertical walls,

the arrangement being such that during the turning of the boat body, the flow regulating vertical walls flex to and fro like plate springs.

2. A water drawing and guiding device for jet-propelled gliding boats as set forth in Claim 1, wherein the cross-sections of the flow regulating vertical walls are made symmetrical and in the form of a basic triangle or trapezoid with its thickness gradually decreasing upward.

3. A water drawing and guiding device for jet-propelled gliding boats as set forth in Claim 1, wherein a partition flow regulating vertical wall is interposed between the flow regulating vertical walls in parallel relation to the latter and is formed so that its cross-sectional is in the form of an isosceles triangle or an isosceles trapezoid with its thickness gradually decreasing upward.

4. A water drawing and guiding device for jet-propelled gliding boats as set forth in Claim 1, wherein the bottom surfaces of the flow regulating vertical walls are V-shaped, as seen laterally of the boat body, gradually downwardly projecting as the approximately intermediate regions are reached.

5. A water drawing and guiding device for jet-propelled gliding boats as set forth in Claim 1, wherein the entire scope gate is colored preferably with a fluorescent coloring agent.

6. A water drawing and guiding device for jet-propelled gliding boats as set forth in Claim 1, wherein the open edges of the attaching seats of the scope gate opposed to the interior of the lattice are formed as slope surfaces rearwardly ascending at given angles.