GB2144311A - A floatable frame member for use in a fish breeding apparatus - Google Patents

Abstract

A floatable frame member for use in a fish breeding apparatus, which is a hollow rod-shaped elastic body constituting a main part of a gas chamber therein, the said elastic body being composed of rubber or rubbery elastic material and reinforced with fiber cords to have an outer diameter of about 279.4-about 609.6 mm (11-24 inches), a thickness of about 12.7-50.8 mm (1/2-2 inches), and a product between a Young's modulus and a sectional secondary moment of 100-3,000 kg . m<2>, and having a ratio of circumferential stress to axial stress of 1.5-2.5 when an internal pressure of 0.1-20 kg/cm<2> is applied to the elastic body. <IMAGE>

Description

SPECIFICATION A Floatable Frame Member for Use in a Fish Breeding Apparatus This invention relates to a floatable frame member for use in a fish breeding apparatus.

In fish breeding apparatus utilizing a net which is used for breeding or catching and preserving fish and shellfish in the interior of the net, the net is hung and supported by a frame body floating on the surface of the sea. In order to enhance the efficiency of breeding or catching and hauling, it is necessary to provide a fish breeding apparatus having a large breeding capacity, particularly a large plane projection area of the fish breeding apparatus.

To this end, a large-scale fish breeding apparatus is constituted by interconnecting a plurality of reinforced hoses each having a strain reinforcing layer embedded therein by means of straight couplings in such a way that the reinforced hoses may be curved to form a substantially circular form of as much as 30100 m in diameter. By such an apparatus, it is possible to realize a large breeding capacity 670 times larger than that of fish breeding apparatus constituted by a rigid frame body of for example steel pipes.However, when the frame body of the former fish breeding apparatus using such reinforced hoses is taken in tow or is subjected to a strong tidal current in the ocean, a strong external force is applied upon the frame body from a specified direction, so that the reinforced hoses forced into the initial bent posture by means of the straight couplings tend to restore to their original linear state.

Consequently, creases with a small radius of curvature are produced in the vicinity of the straight couplings to cause kinking of the reinforced hoses constituting the frame body of the fish breeding apparatus, which may lead to breakage of the hoses.

The applicants have previously described in Japanese Utility Model Registration Application Laid Open No. 57-36,867 (Japanese Utility Model Registration Application No. 55 1 1 1,624) a fish breeding apparatus which can fully tolerate towing and tidal currents.

As shown in Fig. 1 of the accompanying drawings, which is a perspective view of such a known fish breeding apparatus, rod-shaped reinforced elastic members 1 to be charged with a gas are inter-connected by means of bent couplings 2 to form a frame body 3 of polygonal shape having 4-30 sides, for example hexagonal as shown. A fitting portion 5 for a mooring rope 4 is provided on each bent coupling 2, and nets 6 are hung from the frame body 3 of the fish breeding apparatus.

The present invention is a further development of a floatable frame member in such a conventional fish breeding apparatus. More particularly, the invention aims to provide a floatable frame member for use in a large-scale fish breeding apparatus capable of being used in the ocean, which frame member can satisfy various requirements of the frame body of such a fish breeding apparatus.

The conditions required for such a floatable frame member are as follows: (1) To possess enough surf-riding capability to be able to follow the wave surface of a relatively large wave on the ocean without being broken thereby.

(2) To possess such a rigidity as to be free from any abnormal deformation at the fish breeding frame body as well as to resist anti-kinking even when an external force is applied by tidal current in the ocean or by towing the frame body at about 5 knots; (3) To possess such a restoration property as to restore its original profile even if the frame body is bent by the action of an external force which cannot be expected in the case of an ordinary tidal current or towing; (4) To possess enough surplus buoyancy to support the weight of nets, workers, and accessories; (5) To possess enough shock-resisting property against mooring or berthing of a working vessel; and (6) To possess a profile-retaining property which always allows the maintenance of a constant length and diameter irrespective of the application of an internal pressure, for the effective.prevention of the breakage of the hung nets and the prevention of slacking of studs for example for balustrades which are attached around the axis of the floating frame member, and against the leakage of the gas due for example to puncturing.

To this end, following a variety of experiments, the inventors have found that the following characteristics should be met in order that the floatable frame member may satisfy the above requirements.

(a) With respect to the surf-riding property, rigidity and anti-kinking property, it was found through a simulation test in a water pool that it is necessary for the floating frame member to have the product between the Young's modulus and the sectional secondary moment (hereinafter referred to as "El") in a range of 103--104 kg.m2, preferably 5,000 kg.m2. If the El is outside this range, no practical problem occurs with respect to the above three properties.

(b) The restoration property can be fully obtained by use of fiber cords as reinforcing material.

(c) It is necessary for the buoyancy to possess not less than 50 kg/m of surplus buoyancy.

(d) The shock-resisting property can be obtained by a gas-charged hollow construction of a rubber or rubbery elastic material body of which material and structure have elasticity.

(e) The profile-retaining property can be obtained when the ratio of the circumferential stress to the axial stress under an internal pressure is within a range of 1.5-2.5 even if the floating frame member is made of a rubber or rubbery elastic body reinforced with fiber cords.

The present invention aims to provide a floatable frame member having all the above requirements. More particularly, the restoration property can be obtained by making the elastic body constituting the main part of a gas chamber from rubber or rubbery elastic material while being reinforced with organic or inorganic fiber cords. A desired surplus buoyancy can be conferred by designing the outer diameter of this reinforced elastic body to be about 279.4-about 609.6 mm (1 1-24 inches). Enough shockresisting property can be obtained by designing the thickness of this reinforced elastic body which is intended to be charged with a gas such as nitrogen or air to be about 12.7-about 50.8 mm (1/2-2 inches).Moreover, the surf-riding property, rigidity and anti-kinking property which is satisfied when the El of the reinforced elastic body is 103--104 kg.m2 after the internal pressure is applied can be conferred by selecting the material of the elastic member and the number of layers and the inclination angle of the fiber cords in such a manner that the El of the reinforced elastic member itself may be set in a range of 100--3,000 kg.m2, and setting the charged pressure of the reinforced elastic body at 0.1-20 kg/cm2. Further, the profile-retaining property which always allows the maintenance of a constant length and diameter can be conferred when the ratio of the circumferential stress to the axial stress is in a range of 1.5-2.5 under an internal pressure upon the reinforced elastic body.

Accordingly, the present invention provides a floatable frame member for use in a fish breeding apparatus, which is a hollow rod-shaped elastic' body constituting a main part of a gas chamber therein, the said elastic body being composed of rubber or a rubbery elastic material and reinforced with fiber cords to have an outer diameter of about 279.4-about 609.6 mm (11-24 inches), a thickness of about 12.7-50.8 mm (1/2-2 inches) and a product between a Young's modulus and a sectional secondary moment of 100--3,000 kg.m2, and having a ratio of circumferential stress to axial stress of 1.5-2.5 when an internal pressure of 0.1-20 kg/cm2 is applied to the elastic body.

The reason why the outer diameter of the reinforced elastic body is set within a range of about 279.4-609.6 mm (11-24 inches) is that if it is less than about 279.4 mm, the surplus buoyancy of 50 kg/m cannot be obtained, while if it exceeds about 609.6, this is disadvantageous for economic reasons.

The reason why the thickness of the reinforcing elastic body is set within a range of about 12.7 to about 50.8 mm (1/2-2 inches) is that if it is less than about 12.7 mm, it is difficult to maintain the anti-kinking property in connection with the shock-resisting property, the El value of the reinforced elastic member itself and the stress ratio at the time when the internal pressure is charged, while if it exceeds about 50.8 mm, this is disadvantageous for economic reasons.

The reason why fiber cords are employed as the reinforcing material is that fiber cords composed for example of stranded cords of organic fiber, inorganic fiber, or metal fiber possess enough elastically restorative force without being broken or plastically deformed even when the reinforcing elastic body is bent.The reason why the charging pressure is limited to 0.1-20 kg/cm2 is that, as is apparent from the Fig. 2 of the accompanying drawings, which is a graph showing the relation between the curvature, the bending moment and the product El wherein, by way of example, the reinforced elastic member has an outer diameter of 428 mm and a thickness of 24 mm, and is composed of an inner rubber layer, eight cord layers, an intermediate rubber layer, four cord layers, and an outer rubber layer in that order with El=1 ,000 kg.m2, the above range is determined so as to set the El after it is charged with, for instance, nitrogen at 103--104 which satisfies the above various performances. The above minimum value of 0.1 kg/cm2 is applied where even a slight amount of nitrigen gas is charged.It is confirmed that as the El value of the reinforced elastic member itself is increased, the gradient of the curve becomes larger.

Therefore, it is necessary to selectively adopt the charging pressure as well as the El value of the reinforced elastic member itself in order to obtain the desired El value after gas charging. If the El value is less than 100 kg.m2, it is not possible to obtain an appropriate rigidity even when the internal pressure is increased, but within a pressure-tolerable range determined by taking the safety of the rubber frame structure into account, while if the El value exceeds 3,000 kg.m2, it becomes necessary to apply an internal pressure and the economic advantage gained through the application of the internal pressure is lost. Therefore, the value is set within a range of 100--3.000 kg.m2.

The invention will be further described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 is, as previously indicated, a perspective view illustrating a fish breeding apparatus to which the invention is applicable; Fig. 2 is, as previously indicated, a graph illustrating the relation between the curvature, the bending moment and the product El; Fig. 3 is a front view illustrating an embodiment of a frame member according to the invention; Fig. 4 is a front view illustrating a bent coupling; and Fig. 5 is a partially sectional view illustrating a float.

Fig. 3 is an enlarged view illustrating a floatable frame member having an outer diameter of 437 mm, a thickness of 28.5 mm, an overall length of 12.5 m, a charged internal pressure of 5 kg/cm2, a weight of 700 kg and a surplus buoyancy of 100 kg/m. The frame member 11 has at its each end a rigid flange 12 which is to be air-tightly secured to a bent coupling by vulcanization adhesion.

Fig. 4 is a partially sectional view of a bent coupling to which the frame member 11 is to be connected. As a matter of course, the shape of the bent coupling may be selectively determined depending upon the number of frame members 11 required. The bent coupling 13 as shown in Fig. 4 has a flange 1 5 which is provided at one end of the coupling body 14 and is to be airtightly connected to the rigid flange 12, while a connection lobe 1 6 is provided at the curved end of the bent coupling body 14 curved at 60 . The connection lobe 1 6 is to be connected to another straight or bent coupling.The bent coupling 13 has a partition chamber 1 7 formed inside the coupling body 14 which is to communicate with the interior of the frame member 11 and a supply/discharge opening 1 8 which is adapted to charge a gas into the frame member 11 through the chamber 17.

The bent coupling 13 has also an air chamber 19 formed between the chamber 17 and the curved end, which air chamber prevents the penetration of sea water into the inside of the bent coupling.

Numerals 20, 21 and 22 respectively denote a hook to be used as a handle during working such as assembling or conveying, a hook to be used as a fitting portion for a mooring rope, and a stud support respectively.

In assembling the frame body of the fish breeding apparatus from the frame members 11 and the bent couplings 13, each rigid flange 12 provided at each of the ends of the frame member 11 is connected to a bent coupling 13 having an appropriate shape by a sealing material in such a way that an independent gas chamber may be constituted by the hollow space of the frame member 11 and the chamber 17 of the bent coupling 1 3. The provision of independent gas chambers provides the advantage that, even if gas leaks from one frame. member 11 the other gas chambers are not affected.After the above connecting, the required number of frame members 11 are interconnected with one another by means of the bent couplings 13, while a gas such as air or nitrogen is charged into each gas chamber under an internal pressure of 0.1-20 kg/cm2 through a valve (not shown) from the supply/discharge openings 18.

It is preferable that the fish breeding apparatus thus constituted is attached with floats 23 made of foamed styrol to ensure the required buoyancy.

Further, it is also preferable that such a float 23 is covered with a cloth covering for the protection thereof from breakage.

Lastly, this fish breeding frame body is provided with nets, balustrades, supports for nets for preventing fish jumping over, and mooring ropes.

By utilizing such floatable frame members, fish breeding apparatus utilizing the same may exhibit the required surf-riding property, rigidity and antikinking property in use and during towing on the ocean, as well as the required restoration property, surplus buoyancy and shock-resisting property in feeding baits, etc. Further, because of the profile-retaining property of the frame members, it is assuredly possible to prevent breakage of nets and pulling-down of the balustrades and the nets for preventing the jumping-over of the fish in the case of gas leakage.

Therefore, according to the invention, the hollow rod-shaped elastic body constituting the main part of the gas chamber is made of rubber or rubbery elastic material, while it is reinforced with the fiber cords, the outer diameter of the reinforced elastic member being in a range of about 279.4-about 609.6 mm, the thickness thereof being in a range of about 12.7-about 50.8 mm, the El of the reinforced elastic member itself being in a range of 100-3,000 kg.m2, the internal charged pressure of the reinforced elastic member being set in a range of 0.1-20 kg/cm2, and the ratio of the circumferential stress to the axial stress of the reinforced elastic body at the time of internal pressure applied being set at 1.5-2.5. Thereby, sufficient surf-riding property, rigidity, anti-kinking property, surplus buoyancy, shock-resisting property and profile-retaining property can be obtained, so that the invention has the particular advantage that the fish breeding apparatus can be large-scaled for use in the ocean, and that it can be suited for towing.

Claims (2)

1. A floatable frame member for use in a fish breeding apparatus, which is a hollow rod-shaped elastic body constituting a main part of a gas chamber therein, the said elastic body being composed of rubber or a rubbery elastic material and reinforced with fiber cords to have an outer diameter of about 279.4-about 609.6 mm (11-24 inches), a thickness of about 12.7- 50.8 mm (1/2-2 inches) and a product between a Young's modulus and a sectional secondary moment of 100--3,000 kg.m2, and having a ratio of circumferential stress to axial stress of 1.5-2.5 when an internal pressure of 0.1-20 kg/cm2 is applied to the elastic body.

2. A floatable frame member for use in a fish breeding apparatus, according to claim 1, substantially as herein described with reference to, and as shown in, the accompanying drawings.