Pneumatic marine fender

A pneumatic marine fender composed of a cylindrical barrel serving as a shock receiving face, which comprises a composite inner reinforcement composed of two kinds of cord layers which consist of an axially extending cord layer and a circumferentially extending cord layer whose cords are slightly inclined and symmetrically arranged with respect to the circumferential line of the cylindrical shell in reverse directions and helically wound around the cylindrical shell.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a pneumatic marine fender composed of a 
cylindrical barrel serving as a shock receiving face and a method of 
manufacturing the same. 
2. Description of the Prior Art 
The above mentioned kind of pneumatic marine fender composed of a 
cylindrical barrel consists of a hollow cylindrical shell. The cylindrical 
barrel is inflated by applying an internal pressure therein and fitted to 
a ship's side or quay and floated on the sea for the purpose of absorbing 
the dynamic energy arising during the contact between two ships or during 
the berthing of a ship on being moored to a floating body or quay. Such 
pneumatic marine fender makes use of its cylindrical barrel of the hollow 
cylindrical shell as a shock receiving face and can be made expansible and 
contractible by inflating and deflating it, if necessary, and hence is 
particularly adapted to be folded and stored in a simple and convenient 
manner. 
Conventional pneumatic marine fender is formed of rubber or rubber-like 
elastic material and comprises an inner reinforcing layer which is mainly 
arranged in the following two manners: 
(1) Two rubberized cord layers are arranged in axial and circumferential 
directions of the cylindrical barrel, respectively. 
(2) Two rubberized cord layers are inclined at an angle of about 55.degree. 
and symmetrically arranged with respect to the axial direction of the 
cylindrical barrel in reverse directions. 
In the former conventional pneumatic marine fender, the cords of the 
circumferentially extending cord layer are joined together to form seams 
of an endless layer. Such seams have a low tension withstanding ability, 
and as a result, if the cylindrical barrel is subjected to load, the seams 
become excessively elongated. As a result, there is a risk of a distance, 
between adjacent cords of the axially extending cord layer, being enlarged 
or there is a risk of adjacent rows of the cords of the axially extending 
cord layer being disturbed, thereby inducing a premature puncture failure 
of the marine fender. In addition, during shaping of the cylindrical 
barrel in a vulcanization mold, the elongation at the seams results in an 
irregular distance between adjacent cords of the axially extending cord 
layer, thereby making quality of the marine fender irregular. 
In the latter conventional pneumatic marine fender, even though it is 
possible to improve the durability thereof, the energy absorption 
compressive ability becomes inferior to that of the former conventional 
pneumatic marine fender. 
SUMMARY OF THE INVENTION 
An object of the invention, therefore, is to provide a pneumatic marine 
fender composed of a cylindrical barrel serving as a shock receiving face, 
which can exhibit an excellent energy absorption compressive ability which 
is comparable to that of the above mentioned former conventional pneumatic 
marine fender and which can exhibit a berthing shock resistant property or 
durability which is equal or superior to that of the above mentioned 
latter conventional pneumatic marine fender. 
A feature of the invention is the provision of a pneumatic marine fender 
composed of a cylindrical barrel serving as a shock receiving face, 
comprising a hollow cylindrical shell formed of rubber or rubber like 
elastic material and a composite inner reinforcement composed of two kinds 
of cord layers which consist of an axially extending cord layer and a 
circumferentially extending cord layer whose cords are slightly inclined 
and symmetrically arranged with respect to the circumferential line of the 
cylindrical shell in reverse directions and helically wound around the 
cylindrical shell. 
Another feature of the invention is the provision of a method of 
manufacturing a pneumatic marine fender composed of a cylindrical barrel 
serving as a shock receiving face, comprising a step of forming a hollow 
cylindrical shell in which axially extending cord layer including a number 
of cords toroidally arranged in parallel to a center axis of the 
cylindrical shell, a circumferentially extending cord layer including even 
number of cords slightly inclined and symmetrically arranged with respect 
to the circumferential line of the cylindrical shell in reverse directions 
and helically wound around the cylindrical shell and inner and outer 
surface rubber layers are bonded together into the hollow cylindrical 
shell, and a step of hardening and making the hollow cylindrical shell 
into one integral body in a vulcanization mold in which the hollow 
cylindrical shell is put in the vulcanization mold and heated under an 
inflated condition and vulcanized. 
Further objects and features of the invention will be fully understood from 
the following detailed description with reference to the accompanying 
drawings, in which:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a conventional pneumatic marine fender in which cords of two 
rubberized cord layers are arranged in the axial and circumferential 
directions of a cylindrical barrel, respectively. 
FIG. 2 shows another conventional pneumatic marine fender in which cords of 
two rubberized cord layers are inclined at an angle of about 55.degree. 
and symmetrically arranged with respect to the axial direction of the 
cylindrical barrel in reverse directions. 
As described above, in the former conventional pneumatic marine fender 
shown in FIG. 1, opposed ends of each circumferential extending cord are 
connected together to form an endless cord having a seam. The seam has a 
low tension withstanding ability and hence becomes considerably elongated 
when subjected to load, thereby inducing a premature puncture failure as 
described above. On the other hand, the latter conventional pneumatic 
marine fender shown in FIG. 2 has the drawback that the energy absorption 
compressive ability shown by a curve B in FIG. 3 is considerably smaller 
than that of the former conventional marine fender shown by a curve A in 
FIG. 3. 
In the present invention, in order to effectively eliminate local 
concentration of elongation into the seam of the circumferentially 
extending cord layer, use is made of even number of circumferentially 
extending cord layers and the cords of these circumferentially extending 
cord layers are slightly inclined and symmetrically arranged with respect 
to the circumferentially line of the hollow cylindrical shell. 
Experimental tests have demonstrated the result that if the cords of the 
circumferentially extending cord layer of a pneumatic marine fender are 
inclined at an angle of the order of smaller than 30.degree. with respect 
to the circumferential line of the cylindrical barrel, the pneumatic 
marine fender can exhibit the energy absorption compressive ability shown 
by the curve A in FIG. 3 and is capable of effectively dispersing the 
local elongation to be concentrated into the seam of the cords of the 
circumferentially extending cord layer. 
As a result, if the cords of the circumferentially extending cord layer are 
slightly inclined and arranged symmetrically with respect to the 
circumferential line of the cylindrical barrel in reverse directions, it 
is not always necessary to use even number of these cord layers. For 
example, use may be made of one circumferentially extending cord layer and 
the cords thereof may be slightly inclined and arranged symmetrically with 
respect to the circumferential line of the cylindrical barrel in reverse 
directions in the case of vulcanization under pressure. But, for the sake 
of convenience of manufacture, it is preferable to paste together plural 
circumferentially extending cord layers. 
The cord may be formed of organic fiber such, for example, as nylon, rayon, 
polyester or the like, metals such, for example, as a steel wire, steel 
stranded wire or the like and may be used with the aid of means of 
improving the bonding property of the cord with rubber or rubber like 
elastic material. 
As the rubber or rubber-like material, use may be made of natural rubber, 
synthetic rubber such as styrene butadiene rubber or the like or blend of 
these rubbers. It is preferable to provide a cylindrical barrel having an 
outer surface formed of a cut resistant and weather resistant rubber and 
an inner surface formed of a rubber having a high resistance to gas 
penetration. 
FIG. 4 shows a typical embodiment of a pneumatic marine fender according to 
the invention showing a cord arrangement of an inner reinforcement in an 
enlarged scale. Referring to FIG. 4, reference numeral 1 designates a 
marine fender, 2 an axially extending cord layer, 3, 3' circumferentially 
extending cord layers, 4 a metal fitting ring for firmly securing a 
turn-back portion of the axially extending reinforcing cord layer 2 and 5 
an air valve. 
Test pieces of the pneumatic marine fender 1 shown in FIG. 4 and having the 
following two different dimensions are manufactured. 
(1) Outer diameter 200 mm 
Axial length 300 mm 
Cords of the circumferentially extending cord layers 3, 3' are inclined at 
an angle of 19.degree. and symmetrically arranged with respect to the 
circumferential line of the cylindrical barrel in reverse directions. 
(2) Outer diameter 600 mm 
Axial length 1,200 mm 
Cords of the circumferentially extending cord layers 3, 3' are inclined at 
an angle of 20.degree. and symmetrically arranged with respect to the 
circumferential line of the cylindrical barrel in reverse directions. 
Experimental tests on the above two test pieces of the pneumatic marine 
fender according to the invention have yielded the result that both the 
test pieces exhibit excellent energy absorption, compressive ability and 
shock resistant property. 
In the case of manufacturing the former test piece, use is made of a drum 
adapted to be used in the case of molding a pneumatic green tire and 
composed of two halves formed into one integral body, the drum having an 
expansible and contractible outer diameter. About the drum are 
superimposed an inner surface rubber, an axially extending cord layer 
including cords arranged in parallel to the center axis of the drum, 
circumferentially extending cord layers including cords slightly inclined 
and arranged symmetrically with respect to the circumferential line of the 
drum in reverse directions and an outer surface rubber in successin in the 
order as mentioned above and then the drum is expanded until the cords of 
the circumferentially extending cord layers are inclined at an angle of 
19.degree. with respect to the circumferential line of the drum. Each end 
of the cords of the axially extending cord layer is wound around the metal 
fitting ring 4 from the inside toward the outside thereof to form a 
turn-back portion and subsequently the end surface of the drum is 
subjected to a working of covering the turn-back portion with the outer 
surface rubber, thereby forming a green case. Subsequently, the drum is 
contracted to reduce its outer diameter, thereby permitting to extract the 
green case therefrom. 
In the case of manufacturing the latter test piece, use is made of a mold 
in which an outer surface rubber, two circumferentially extending cord 
layers whose cords are slightly inclined and arranged symmetrically with 
respect to the circumferential line in reverse directions, an axially 
extending cord layer whose cords extend in parallel to the center axis of 
the mold and an inner surface rubber are pasted together into one integral 
body and at the same time each end surface inclusive of the turn-back 
portion of the axially extending cord layer is reinforced to form a green 
case in the mold. 
In the case of manufacturing both the test pieces, the circumferentially 
extending cord layers surrounding the axially extending cord layer 
including cords extending in parallel to the center axis of the 
cylindrical barrel and including cords slightly inclined and symmetrically 
arranged with respect to the circumferential line in reverse directions 
are obtained by cutting parallel cords along inclined lines spaced apart 
from each other by a distance which is equal to the barrel length of the 
cylindrical barrel and inclined at an angle of 71.degree. with respect to 
the axial direction of the cords, as shown in FIG. 5. 
Then, the inclined cut ends of the cords are aligned along one end of the 
cylindrical barrel as shown in FIG. 6 and helically wound around the 
cylindrical barrel to obtain helically formed cord arrangement. It is a 
matter of course that the green case is inflated and then put into a 
valcanization mold where the green case is heated and vulcanized under 
pressure. 
During the vulcanization, the cord layers are uniformly subjected to 
tension due to the internal pressure applied in the green case so as to 
forcedly reduce the cord angle. As a result, there is no risk of the 
distance between adjacent cords of the axially extending cord layer being 
irregular, thereby preventing the quality of the marine fender in the 
circumferential direction from becomming nonuniform. 
The above mentioned mode of the internal pressure subjected to the green 
case is the same as the berthing load subjected to the marine fender when 
it is used. As a result, there is no risk of the seam of the cords of the 
circumferentially extending cord layer being subjected to the local load 
or stress concentration. 
As stated hereinbefore, the pneumatic marine fender according to the 
invention is capable of eliminating a difficult problem which has been 
encountered with the seam of cords of the circumferentially extending cord 
layer without requiring any specially precise measures in the 
manufacturing step and capable of effectively improving the wear resistant 
property of the marine fender without deteriorating the energy absorption 
compressive characteristic thereof.