Patent Grant
6915820
Our present invention relates to an automotive vehicle tubing intended especially for use with liquids common in automotive applications such as fuel (gasoline or diesel fuel) and hydraulic fluid such as brake fluid. More particularly, the invention relates to tubing for such purposes wherein a metallic inner tube has an aluminum tubing and a polyamide layer on such coating.
Automotive vehicle tubing of the type described is designed to minimize corrosion and abrasive wear and, therefore, to be capable of use where the tubing is exposed to the elements, for example, on the underside of a vehicle chassis.
The aluminum coating may additionally have a chromate coating between the polyamide layer and the aluminum and in the past the polyamide or nylon coating has been composed of polyamide-11 (nylon-11) applied as a powder coating. In practice it has been found that the corrosion-resistance and abrasion-resistance of such tubing can be further improved.
It is, therefore, the principal object of the present invention to provide an improved automotive vehicle tubing, especially for use with automotive vehicle fuels and hydraulic fluids in which the corrosion-resistance and abrasion-resistance are enhanced.
Another object of this invention is to provide a tubing for the purposes described but which is free from drawbacks of earlier composite tubing.
These objects are achieved, in accordance with the invention, by providing a polyamide or nylon layer of polyamide-12 or nylon 12 which is extruded onto the aluminum coating. More particularly, the automotive fluid tubing of the present invention can comprise:
a metallic inner pipe;
an aluminum coating on an exterior of the inner pipe; and
a polyamide-12 layer extruded onto and bonded to the aluminum coating.
The term “polyamide-12” is used here interchangeably with nylon 12.
Surprisingly, the combination of an aluminum coating on the metallic inner pipe and a polyamide-12 layer extruded onto and around the aluminum coating can provide a substantially better abrasion-resistance than has been obtainable heretofore. Indeed, tests have shown that with automotive vehicle tubing of the invention an improvement in abrasion-resistance by at least 30% can be obtained.
The inner pipe can be composed of steel and can be fabricated in a simple manner, e.g. by rolling a steel strip through 360° and welding the abutment edges together with a longitudinal butt-weld seam. Alternatively, a doubly rolled inner pipe can be fabricated in which the strip is rolled through 720° and where two turns of the rolled pipe are joined by soldering. The metallic inner pipe can have a wall thickness of 0.2 to 8 mm, preferably 0.4 to 1.5 mm.
According to a feature of the invention the aluminum coating is a hot-dip aluminum coating formed by passing the metal pipe through an aluminum melt which completely wets the external surface of the inner pipe. Excess melt is blown off by gas jet and the layer thickness of the hot-melt aluminum coating is controlled to be 50 to 200 μm, preferably 100 to 140 μm.
The polyamide-12 layer can also include substances for enabling the electrostatic bonding thereof at its inner side to the outer surface of the tube and the additives for that purpose can include conductive carbon black, graphite fibers and/or carbon fibers. The polyamide-12 layer should have a thickness of 50 to 200 μm, preferably 100 to 140 μm.
According to a further feature of the invention, the aluminum coating can be provided with a chromium-free surface treatment layer, especially a phosphatizing coating and/or a primer coating which will be disposed between the aluminum coating and the polyamide-12 layer. These coatings increase the corrosion and wear-resistance and particularly improve the adhesion of the polyamide-12 layer to the metal pipe.
The chromium-free surface treatment coating can have a thickness of 0.2 to 0.8 μm and is preferably small than 0.5 μm. The primer coating can have a thickness of 1 to 8 μm, preferably 3 to 5 μm. Because the product may be subject to mechanical and thermal stress when in place and when being installed in an engine compartment or on the underside of the chassis, and to reduce noise produced by the tubing, on the outer side of the polyamide-12 layer a protective layer of a thermoplastic elastomer or polypropylene can be applied. The coating can have a thickness of 1 to 3 mm, preferably 1.5 to 2 mm.
The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:
From
On the outer side of this inner pipe 1 a hot-dipped aluminum coating 2 of a thickness of about 120 μm is applied. On the aluminum coating 2 a chrome-free surface treatment layer 3 in the form of a phosphate coating is applied with a thickness of say 0.4 μm on the phosphate coating 3, a 5 μm thick primer coating 4 of a commercial nylon primer is applied. A polyamide-12 layer 5 of 120 μm is extruded onto the primer coating and can be covered by a protective layer of a thickness of about 2 mm of a thermoplastic elastomer or polypropylene. This layer is designated as 6.
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| Number | Name | Date | Kind |
|---|---|---|---|
| 5182074 | Yoshioka et al. | Jan 1993 | A |
| 5590691 | Iorio et al. | Jan 1997 | A |
| 5662145 | Stagg | Sep 1997 | A |
| 5867883 | Iorio et al. | Feb 1999 | A |
| 5972450 | Hsich et al. | Oct 1999 | A |
| 6003562 | Iorio et al. | Dec 1999 | A |
| 6245183 | Iorio et al. | Jun 2001 | B1 |
| 6267148 | Katayama et al. | Jul 2001 | B1 |
| 20020005223 | Campagna et al. | Jan 2002 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20040035486 A1 | Feb 2004 | US |
