Pipes and tubular conduits – Flexible – Corrugated
Reexamination Certificate
2000-03-24
2001-11-27
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
Flexible
Corrugated
C138S137000, C138S141000, C138SDIG007
Reexamination Certificate
active
06321794
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a corrugated or convoluted laminated tube having a wall corrugated or convoluted along at least a portion thereof. The corrugated or convoluted laminated tube of this invention is suitable for use in, for example, a pipeline for automobile fuel (such as gasoline, gasoline containing alcohol, alcohol or hydrogen), or for fuel vapor.
2. Description of the Related Art
It has been usual to use a tube of a polyamide, or other resin, in a pipeline for automobile fuel, or fuel vapor. The resin tube has a low fuel permeability, and a high impact strength.
It has sometimes been the case to use a corrugated or convoluted resin tube having a corrugated or convoluted wall rather than a smooth one having a smooth wall, for the reasons as stated at (1) to (3) below:
(1) A corrugated or convoluted tube is superior to a smooth one in flexibility. Therefore, it can effectively absorb vibration and follow a fairly large relative displacement between the members connected to its opposite ends, respectively.
(2) A corrugated or convoluted tube is superior to a smooth one in deformability and expansibility. Therefore, it can tolerate any abnormal displacement occurring from, for example, the collision of the automobile, and can be bent at a relatively small angle to adapt itself to a limited space available when used for making a pipeline.
(3) In addition, it is superior to a smooth tube in collapsing strength owing to its structural features.
In order to ensure its merits as stated at (1) to (3) above, however, it is necessary for a corrugated or convoluted tube to have its corrugated or convoluted wall formed with a thickness which is smaller than the wall thickness of a smooth tube. Moreover, a corrugated or convoluted wall portion formed along a portion of a tube is smaller in thickness than any smooth wall portion thereof, since such a corrugated or convoluted wall portion is formed by corrugating a portion of the wall of a tube extruded with a uniform wall thickness.
Therefore, it is feared that a corrugated or convoluted tube may be more permeable to fuel because of the smaller thickness of its corrugated or convoluted wall.
Moreover, polyamide, or other particular resins are very likely to swell with fuel if they remain in contact with fuel, or fuel vapor at a high temperature for a long time. If such swelling occurs to a corrugated or convoluted wall of the resin tube, the expansion of its corrugations or convolutions causes the tube to undergo heavy axial expansion and thereby to be permanently deformed.
As a result, the corrugated or convoluted tube is likely to be deformed in such a way as to project from the space available for it and interfere undesirably with any component or part situated around it.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a corrugated or convoluted tube having a wall of low fuel permeability and resisting any deformation as mentioned above, while retaining its merits as stated at (1) to (3) above.
This object is attained by a corrugated or convoluted laminated tube having a wall corrugated or convoluted along at least a portion thereof, the wall comprising at least an outer resin layer and an inner resin layer bonded thereto, the inner resin layer being formed from a THV (tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride) terpolymer satisfying at least one of two conditions as stated at (1) and (2) below:
(1) The terpolymer has a monomer composition consisting of 30 to 80% (by weight throughout this specification) of tetrafluoroethylene, 10 to 30% of hexafluoropropylene and 10 to 50% of vinylidene fluoride; and
(2) It has a flexural modulus of 40 MPa or above.
The corrugated or convoluted tube of this invention composed as described above has only a low fuel permeability even if it may have a small wall thickness, since the THV terpolymer is an excellent fuel barrier.
Therefore, if a corrugated or convoluted tube is formed with a small wall thickness, its merits including flexibility, deformability and expansibility can fully be manifested. The THV terpolymer can effectively be used to make a corrugated or convoluted tube exhibiting its characteristic flexibility, deformability and expansibility, since it is the softest material among the fluororesins which are generally hard.
Thus, the corrugated or convoluted laminated tube of this invention satisfies various requirements expected from a corrugated or convoluted tube when it is used in, for example, a pipeline for fuel in an automobile, including its property of absorbing vibration effectively, its adaptability to any abnormal displacement resulting from the collision of the automobile and its relatively high bending deformability which is beneficial when it is used for laying out the pipeline.
A THV terpolymer having a monomer composition failing to fall within the ranges of weight proportions as defined at (1) above, and a flexural modulus lower than 40 MPa is, however, not suitable, since it is not satisfactorily low in fuel permeability. Such a THV terpolymer belongs to the category of “fluororubbers”.
The outer resin layer protects the corrugated or convoluted tube from various kinds of external impact or changes. Even if the outer resin layer may be formed from a resin which swells with fuel easily (e.g. polyamide), it is possible to prevent its swelling with fuel and thereby any elongation of the tube, since its THV layer cuts off fuel effectively.
The above and other objects, features and advantages of this invention will become more apparent from the following description and the accompanying drawings.
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Ishida Yoshimitsu
Ito Hiroaki
Ito Tomohide
Miyajima Atsuo
Brinson Patrick
Holman PLLC Jacobson
Tokai Rubber Industries Ltd.
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