Machine element or mechanism – Control lever and linkage systems – Hand operated
Reexamination Certificate
1999-03-16
2001-04-17
Green, Mary Ann (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Hand operated
C074S500500
Reexamination Certificate
active
06216554
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention related to a control cable comprising an outer casing and an inner cable slidably inserted into said outer casing and more particularly to such control cable drastically improved in its durability as well as its loading efficiency.
2. Description of the Prior Art
It is well known to coat an outer peripheral surface of the inner cable with a synthetic resin film as an inner coating and to provide the inner peripheral surface of the outer casing with a synthetic resin liner in order to improve durability and the loading efficiency of the control cable. For example, Japanese Patent No. 2664435 discloses a control cable in which a polyamide resin composition is used as the inner coating and a polybutylene terephthalate resin composition is used as the liner. However, in this control cable of the prior art, said liner contains an amount of filler substantially comprising potassium titanate whisker. As is well known to those skilled in the art, use of this potassium titanate whisker is disadvantageous from the viewpoints of its high cost as well as of its relatively low durability.
SUMMARY OF THE INVENTION
In view of the problem as has been described above, it is a principal object of the invention to provide a control cable remarkable improved in its durability as well as its loading efficiency using an inexpensive material.
The object set forth above is achieved, according to the invention, by a control cable comprising an outer casing an inner cable slidably inserted into said outer casing, wherein said inner cable is provided on its outer peripheral surface with inner coating formed by a polyamide synthetic resin while said outer casing is provided on its inner peripheral surface with a liner formed by a mixture of polybutylene terephthalatate and polybutylene decanedicarboxyplate copolymer and an elastomer having an epoxy radical containing an olefinic copolymer as an essential ingredient where the content of said elastomer is 0-30% by weight of the total resin composition.
Preferably, said inner coating presents a modulus of bending elasticity of 8400-13500 kg/cm
2
in its water-soaked state (50% saturated at 23° C.).
More preferably, said liner presents a modulus of bending elasticity of 3300-8000 kg/cm
2
which is lower than the modulus of bending elasticity of said inner coating as measured according to ASTM D790.
The copolymer PBT/D used as the resinous composition to form the liner according to the invention is the copolymer (PBT/D) and it comprises polybutylene terephthalate (PBT) obtained by condensation polymerizing terephthalic acid with 1, 4-butanediol, on one hand, and polybutylene decanedicarboxylate (PBD) obtained by condensation polymerizing decanedicarboxylic acid with 1, 4-butanediol, on the other hand. The modulus of bending elasticity of the composition according to the invention is in a range of 3300-8000 kg/cm
2
and a mol ratio between PBT and PBD is not critical. Accordingly, a mixture of two or more PBT/Ds having different mol ratios as well as a mixture of PBT and PST/D may be used in the practice of the invention. A substantial mol ratio of PBT/D is usually selected in a range of 95/5~80/20.
The epoxy radical containing an olefinic copolymer used as the resinous composition forming the liner according to the invention is the olefinic copolymer which contains the epoxy radical in its side chain or main chain but no so-called expoxy resin. Examples of such epoxy radical containing an olefinic copolymer include olefinic copolymer having glycidyl radical such as glycidyl ester, glycidyl ether or glycidyl amine in its side chain and a double bond containing an olefinic copolymer in which said double bond is epoxidated. Of these epoxy radical containing olefinic copolymers, a copolymer comprising &agr;—olefin and glycidyl ester of &agr;, &bgr;—unsaturated acid is preferably used in the invention. Examples of &bgr;—olefins include ethylene, propylene and butene-1. Glycidyl ester of &agr;, &bgr;—unsaturated acid is a compound represented by a formula 1 as indicated below and specific examples thereof include glycidyl acrylate, glycidyl methacrylate and glycidyl ethacrylate:
(R represents hydrogen atom or lower alkyl)
Content of an epoxy radical in said epoxy radical containing olefinic copolymer is usually in a range of 0.1~30% weight, preferably in a range of 0.2-20% by weight. The content lower than 0.1% by weight could not achieve a desired effect through a desired reaction with PBT/D and the content higher than 30% by weight would cause a gelation during melt kneading with PBT/D, inevitably deteriorating the extrusion stability, moldability and mechanical properties of such material.
It is also possible to copolymerize the other olefinic monomer such as methyl acrylate, methyl methacrylate, acrylonitril, styrene, vinyl acetate or vinyl ether so far as the desired effect of the invention is not adversely affected thereby.
Examples of the elastomer used with the epoxy radical containing an olefinic copolymer as the resinous comosition forming the liner according to the invention may be a polyolefin elastomer, diene elastomer, acryl elastomer, polyamide elastomer, polyester elastomer, silicone elastomer, fluoroelastomer and polysulfide elastomer. One or more of these elastomers may be used in the practice of the invention.
The content of the copolymer PBT/D ingredient in the resinous composition forming the liner according to the invention is in a range of 70-100% by weight and a modulus of bending elasticity of the composition according to the invention is selected in a range of 3300~8000 kg/cm
2
. The content lower than 70% by weight would disadvantageously result in a poor heat resistance of the control cable. The content of the epoxy radical containing an olefinic copolymer ingredient in the resinous composition forming the liner according to the invention is in a range of 0~30% by weight and a modulus of bending elasticity of the composition according to the invention is selected in a range of 3300-8000 kg/cm
2
, more preferably in a range of 5~20% by weight. A modulus of bending elasticity higher than 800 kg/cm
2
would result in the deterioration of the loading efficiency and a modulus of bending elasticity lower than 3300 kg/cm
2
would decrease the durability.
While a melt viscosity of the resinous composition sued to form the liner according to the invention is not critical so long as it allows extrusion of the liner to be effectively achieved, the melt viscosity is selected so that a melt flow rate of 1~30 g/10 min, preferably a melt flow rate of 1~20 g/10 min and more preferably a melt flow rate of 1~10 g/min may be obtained at a temperature of 250° C. under a load of 1 kg.
Preparation of the resinous composition used to form the liner according to the invention is not limited to a specific process. For example, powder, pellet or flake of PBT/D and elastomer may be dry blended using suitable means such as a ribbon blender, Henschel mixer or V-blender and then melt kneaded using suitable means such as a Banbury mixer, a mixing roll, a single-screw or twin-screw extruder or a kneader. Alternatively, it is also possible to feed said materials successively to a melt kneading apparatus without the previous step of dry blending. As the most typical process of these various processes, said materials may be melt kneaded using the single-screw or a twin-screw extruder having a sufficient kneading force.
Though not essential ingredients for the resinous composition used to form the liner according to the invention, lubricant such as polytetrafluoroethylene, silicone oil, molybdenum dioxide, graphite or boron nitride may be added in a range of less than 10% by weight in order to improve slidability.
If it is desired, fibrous and/or granular reinforcement may be added to the resinous composition used to form the liner according to the invention so far as such reinforcement does not adversely affect the invention.
Examples of such reinforcement include inorganic fiber such as glass fiber, a
Aoki Masahiko
Kimura Hiroshi
Nagayoshi Kanji
Nishida Ken'ichi
Chuohatsujo Kabushiki Kaisha
Green Mary Ann
Siegel Lackenbach
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