JPS6055644B2 - Foam-filled fender - Google Patents

Description

[Detailed description of the invention] [Scope of application of the invention] The present invention relates to improvements in foam-filled fenders.

[Background of the invention]

Foam-filled fenders are fenders in which a core (usually cylindrical) made of elastic foam is surrounded by a rubber skin.

Similar to pneumatic fenders, which are made by filling air inside a rubber shell reinforced with fiber cords, this type of fender is itself floating and provides constant protection regardless of the height of the tide. Because it has the characteristic of exhibiting glare performance, it has unique uses as anti-glare equipment in ports and sea berths with large tidal differences, and as a cushioning material for vessels coming alongside each other offshore, and is also used as a pneumatic fender as mentioned above. In recent years, this type of Demand for fender materials is increasing. [Problems to be solved] By the way, the core of the known form-filled fender is
Since all so far have been made from a single type of elastic foam (eg, single expansion ratio), their performance naturally depends on the shock absorption capacity and reaction force properties of the foam used.

For this reason, the foam itself is required to be of high quality with excellent properties, and the cost of the foam occupies a very large proportion of the product cost. Therefore, if it is possible to obtain a core with a low cost per unit of absorbed energy by some means, it will not only be beneficial for both manufacturers and users, but also have the effect of reducing the amount of manufacturing and installation materials. This will enable us to cooperate with requests for resource conservation. [Purpose of the Invention] The present invention attempts to solve the above-mentioned problems by using a novel structure in which the core body is composed of a plurality of elastic foams having different expansion ratios, which has not been considered in the past. It is.

[Specific configuration]

The present invention provides a form-filled fender comprising a core made of an elastic foam and an outer skin made of a rubber elastic material covering the periphery of the core, in which the core has different foaming ratios. Consisting of multiple foam layers, the innermost foam layer has a foaming ratio of 1 K or more, and the outer foam layers have a higher foaming ratio than the innermost foam layers. It is characterized by

Prior to developing the above-mentioned specific configuration, the inventor of the present invention questioned the existing concept of a single composition core material in the process of considering various measures to improve the performance of foam-filled fenders. We focused on the differences in the degree of compression between sections when a fender with a circular cross section is compressed in the diametrical direction.

Figure 1 schematically shows the state in which the form-filled fender 1 is compressed against the rigid surface 2. On the other hand, when a compressive force is applied in the right angle direction, it becomes flattened as shown in Figure B, but at this time, both end portions 1b, 1b shown by rough crosshatching hardly receive any compressive deformation, and absorb energy due to deformation. It can be seen that the reaction force is mainly exerted on the central portion 1a. That is, both end portions of the fender 1 parallel to the compression direction (plano-convex lens-shaped portions separated by a circular arc and a chord) do not significantly participate in the buffering effect. Therefore, the performance of the fender depends to a large extent on the properties of the central portion 1a. This consideration may seem obvious at first glance, but it is an important matter that led to the invention. Based on the above estimation, the present inventor prototyped four types of test fender core bodies shown in FIG. 2 and compared their fender performance.

Incidentally, the foams used in this experiment were made of polyethylene, and the foaming ratios were 1@ (symbol F-10) and 2@ (symbol F-20), respectively. The specifications of each sample were as shown in the table below (Table 1). As shown in the above table, since the expansion ratios of Samples A and B are 2:1, the reaction force and energy each exhibit a relationship of approximately 1:2.

The performance of sample A, which is made only of foam material F-20 with a high expansion ratio, is almost the same as that of the pneumatic fender material. However, sample C consists of high-rate foam material F-20 and low-rate foam material F-1.
Even though the volumes of samples A and B1 are the same, their reaction force and absorbed energy values are larger than the average values of samples A and B1. In other words, it can be seen that the properties per unit volume are improved by forming a double structure in which the foaming ratio in the center is lower than that in the peripheral region. Therefore, in order to clarify this fact, the results of comparing each sample with the performance of sample A at 60% compression set as 100 are shown in Table 3 below.

Incidentally, the structure of the stacked structure used as a comparison is schematically shown in FIG. 2
? ? ? L-j In the above table, sample A
and B are both a single structure made of an elastic foam material with a single expansion ratio.

, Sample C has a volume ratio of foam materials F-10 and F-20 of 50/50, but the same thickness of foam material F-10 and F-20 shown in the right column
Comparing the theoretical values obtained when -10 and F-20 are superimposed with Sample C, Sample C is superior in both reaction force and absorbed energy. Similarly, sample D and the foam materials F-10 and F-2 shown on the right side
Even when compared with the theoretical value of a superimposed structure in which the volume ratio of 0 is 75/25, the performance of sample D is still superior, proving the superiority of the double structure. Figure 4 shows the high-rate foam material F-20 and the low-rate foam material F- in the above double structure.
The graph shows the change in absorbed energy per unit cost (based on sample A) when the volume ratio of F-10 is changed stepwise.From this graph, the theoretical superposition value for the combination of F-10 and F-20 is shown. A positive distance between the diagonal straight line shown and the arcuate line showing the double structure case indicates the improvement effect of the present invention, and the improvement effect is obtained when the volume ratio of F-20/F-10 is 60/40 or It can be seen that in the vicinity of 50/50, there is an improvement of about 10% compared to the case of F-20 alone and about 3.5% compared to the case of F-10 alone. The specific configuration of the present invention described above is based on the above findings.

In addition, in this configuration, the meaning of high or low foaming ratio is strictly relative and does not mean high or low from a technical concept, so in reality, the outer foam layer is It is sufficient if the foaming ratio is higher than that of the foam layer. However, when designing fenders, the value of absorbed energy is the first prerequisite, so the core material is selected based on this value, the allowable large compression ratio, and the fender dimensions (diameter, length, etc.). The foaming ratio is determined. However, the innermost foam layer is 10ff1
It is necessary that the foaming ratio be higher than or equal to the foaming ratio. Furthermore, since the simple superposition theory does not apply to the double structure of the present invention, it is preferable that the actual design be based on the results of experiments on small models. Since the core material of the fender according to the present invention is repeatedly compressed and deformed by coming alongside, it must have sufficient mechanical strength, especially cyclic fatigue strength.

In this respect, foams made of natural rubber or synthetic rubber such as urethane rubber are the best. In particular, polyurethane foam
Since it can be foamed in one shot using a liquid base polymer, and foaming occurs simply by adding water to the raw material, it is suitable as a core material for small form-filled fenders. In addition, materials other than the above natural rubber and synthetic rubber, such as polystyrene, polyethylene, etc.
B.S. EVA. Highly elastic synthetic resin foams such as sEPRl polyvinyl chloride can optionally be used. On the other hand, in the case of large fenders, the foam molding method has drawbacks such as the cost of the mold and the uniformity of foaming, so sheets of relatively inexpensive foam such as polyethylene foam are rolled up into cylindrical shapes. The molding method is highly practical. The fender of the present invention may be the same as conventional form-filled fenders except that the core has a multilayer structure.

Depending on the installation method, this type of fender has either a shaft pipe in the center and a hanging rod inserted through the shaft pipe, or a type in which the outer circumferential surface is covered with a hanging net. However, in either type, the outer periphery of the core should be covered with a tough outer skin.

〔Example〕

FIGS. 5 and 6 are a partially cutaway longitudinal sectional view and a cross sectional view of a form-filled fender having a built-in shaft tube in the center according to an embodiment of the present invention.

In the fender of this example, a double flanged shaft tube 2 passes through the center of a cylindrical core 1. The core body 1 includes a first foam layer 1a made of a low-rate foam (10 times foaming) and a second foam layer 1b made of a high-rate foam (2-layer foam) in a volume ratio of 50/50.
, and a non-foamed rubber outer skin 3 covers both of them. The end surface portion 3a of the outer skin 3 completely surrounds the inner collar 4 and is in close contact with the outer circumferential surface of both ends of the shaft tube 2 and the inner surface of the outer collar 5. In addition, there are many small holes 6, 6, around the inner tsuba 4.
... are bored, and the end surface portion 3a of the outer skin 3 is integrated with the collar 4 through these small holes 6, 6, .... The outer collar 5 has a rotatable stirrup 7 in its center, and is moored to an installation location such as a pier using a mooring device such as a chain or a robe. In the above example product, the core body is the first foam layer of 1C@foam and the core of 2CP@foam. Pre-volume ratio of foam to second foam layer: 5
Since it has a 0/50 double structure, the absorbed energy per unit cost is greater than that of conventional products using a single foam, making it possible to produce fenders that are cheaper. can. In addition to the unique effects of the present invention described above, this example fender has a double-flange shaft tube, so that peeling of the outer skin from the shaft tube due to shearing action when coming alongside is virtually prevented. In addition, it eliminates the need for equipment such as a mounting shaft that passes through the shaft pipe, and has secondary effects such as substantially preventing damage to the end face of the fender in the vicinity of the shaft pipe opening. 7th
The figures and FIG. 8 show an example of a double-structure foam-filled fender of a shaftless tube type.

This example is the same as the previous example except that the central part of the core body 1 is not provided with the shaft tube 2 in the previous example. A net (not shown) is used to anchor this fender. What is shown in FIG. 9 is an example in which a third foam layer 1c, which is also highly foamed, is replaceably laminated on a second foam layer 1b, which is also highly foamed. Note that it is also possible to divide the high-rate foam layer 1b into more layers. As described above, it should be understood that the one-double structure referred to in the present invention is a macroscopic concept. Furthermore, in the examples shown in FIGS. 5 and 6, the high-rate foam layer 1b may be separable from the low-rate foam layer 1a.

〔Effect of the invention〕

As detailed above, according to the present invention, the cost of raw materials can be reduced without deteriorating the performance of form-filled fenders, so it has great value in terms of port facilities and resource conservation. That is clear.

[Brief explanation of the drawing]

Fig. 1 is a model diagram explaining the principle of the form-filled fender of the present invention, and Fig. 2 is a model diagram showing the schematic structure of the form-filled fender of the present invention and a conventional form-filled fender. , FIG. 3 shows the overlapping structure E, . Schematic diagram of the overlapping structure corresponding to F (Figure a (=E), Figure b (=F), Figure 4 shows the relationship between volume ratio and energy absorption per unit cost in double structure foam. Graphs, FIGS. 5 and 6 are partially cutaway longitudinal and cross-sectional views of a form-filled fender according to one embodiment of the present invention, and FIGS. 7 and 8 are according to another embodiment. Fig. 9 is a partially cutaway vertical cross-sectional view and a cross-sectional view showing a further embodiment of the fender. The meanings of the symbols in each figure are as follows. DF: fender, 1
: core body, 1a: first foam layer, 1b: second foam layer, 1
c: third foam layer, 2: shaft tube, 3: outer skin, 4, 5: tsuba,
6: small hole, 7: stirrup.

Claims (1)

[Claims] 1. In a form-filled fender consisting of a core made of an elastic foam and an outer skin made of a rubber elastic material covering the periphery of the core, the core contains a plurality of foams having different expansion ratios. The innermost foam layer has a foaming ratio of 10 times or more, and the outer foam layer has a higher foaming ratio than the innermost foam layer. A foam-filled fender featuring: