Fishing – trapping – and vermin destroying – Fishing – Lines and/or leaders
Reexamination Certificate
1999-01-12
2001-01-09
Thomas, Alexander S. (Department: 1772)
Fishing, trapping, and vermin destroying
Fishing
Lines and/or leaders
Reexamination Certificate
active
06170192
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a leader for fly fishing. More particularly, the present invention relates to a leader for fly fishing, which comprises a butt section, a tapered section and a tippet section; comprises a vinylidene fluoride-based resin whose viscosity lies in a specific range, thereby exhibiting a high tensile strength or tenacity; and is so improved as to inhibit a shape-unstable portion (constriction) having a smaller diameter than an average diameter of the tippet section, and melt fracture from being formed at a connecting portion between the tapered section and the tippet section, thereby exhibiting an excellent natural drift property.
BACKGROUND ART
The fly fishing is a fishing method of casting a fly without weight and float from a remote position unable to be sensed by fishes, and drifting the fly on or in water. To meet such requirements, in the fly fishing, there has been used a five-part fishing equipment comprising a fly rod, a reel, a fly line, a leader and a fly.
Among these parts, as the leader, there have been preferably used those leaders which are reduced in thread diameter to realize natural drift thereof. The leader has been further required to have a tapered section through which an inertia force is smoothly transmitted from the fly line to the fly upon casting, thereby enabling the fly to be quietly dropped on a water surface. Consequently, the leader has been usually composed of a portion called “butt” and having a larger thread diameter, which is connected with the fly line, a portion called “taper” and having a tapered shape, and a portion called “tippet” and having a smaller thread diameter, at which the fly is fitted to the leader. Incidentally, in FIG.
1
(
a
) showing an explanatory view of the above-mentioned leader, reference numeral (
1
) represents the leader, (
2
) represents the butt section (A), (
3
) represents the tapered section (B), and (
4
) represents the tippet section (C).
In addition, the leader is preferably comprising a material whose refractive index is close to that of water, so as to be unsensed by fishes. As such the materials having a refractive index close to that of water, there may be exemplified vinylidene fluoride-based resins. However, when the vinylidene fluoride-based resins are subjected to spinning process, it has been difficult to obtain a leader having a smooth shape. Especially, in the production of a tapered leader, a shape-unstable portion
6
(constriction) having a smaller diameter than an average diameter of the tipped section is formed at a connecting portion between the tapered section (B) and the tippet section (C), so that a stress due to tension caused upon fishing-up is concentrated on the constricted portion, thereby causing the leader to be cut thereat.
Further, in the case where the vinylidene fluoride-based resins are subjected to the spinning process, the obtained leader tends to suffer from melt fracture. Especially, the melt fracture is more remarkably caused upon the production of tapered leaders. That is, since the tapered leader is composed of the butt section (A), the tapered section (B) and the tippet section (C), it is required that the diameter of the leader is varied corresponding to the respective sections, so that the melt fracture is likely to occur. When a raw thread having such melt fracture is stretched to impart a mechanical strength thereto, the raw thread not only suffers from breakage but also is deteriorated in appearance of the surface thereof. Further, when vinylidene fluoride-based resins having an inherent viscosity less than the specific value is used to produce a leader, the obtained leader is deteriorated in natural drift property.
The present invention has been attained to overcome the above-mentioned problems. It is an object of the present invention to provide a leader for fly fishing which comprises a vinylidene fluoride-based resin, can show a high tensile strength or tenacity, is improved so as to inhibit a shape-unstable portion
6
(constriction) having a smaller diameter than an average diameter of the tippet section and melt fracture from being formed at a connecting portion between the tapered section (B) and the tippet section (C), and can exhibit an excellent natural drift property and a good appearance.
DISCLOSURE OF THE INVENTION
That is, in an aspect of the present invention, there is provided a leader for fly fishing, which comprises a vinylidene fluoride-based resin, and comprises a butt section, a tapered section and a tippet section, the inherent viscosity of the vinylidene fluoride-based resin being 1.0 to 1.7 dl/g.
The present invention is explained in detail below. The leader for fly fishing according to the present invention (hereinafter referred to merely as “leader”) is formed of a vinylidene fluoride resin-based monofilament, and is a so-called knotless tapered leader. As the vinylidene fluoride-based resin as a raw material, there may be exemplified vinylidene fluoride-based homopolymers, vinylidene fluoride-based copolymers or a mixture thereof.
It is necessary that the vinylidene fluoride-based copolymers are selected from those capable of exhibiting a ductility and a strength which are acceptable for the knotless tapered leader. As the vinylidene fluoride-based copolymers capable of satisfying these requirements, there may be exemplified copolymers of vinylidene fluoride and ethylene tetrafluoride, propylene hexafluoride, ethylene trifluoride, ethylene chloride trifluoride, vinyl fluoride or the like. These monomers other than vinylidene fluoride can be used singly or in combination of two or more thereof.
The inherent viscosity of the vinylidene fluoride-based resin as a raw resin of the leader, is 1.0 to 1.7 dl/g, preferably 1.10 to 1.35 dl/g, more preferably 1.15 to 1.35 dl/g, still more preferably 1.20 to 1.35 dl/g. When the inherent viscosity is less than 1.0 dl/g, the obtained leader cannot have a high tensile tenacity and it becomes difficult to control a length of the leader upon the production thereof, resulting in too long tapered section. The leader for fly fishing has been usually sold and used by a predetermined length, so that when the tapered section is elongated, the lengths of the remaining butt and tippet sections can no longer be increased. It is disadvantageous that such a leader cannot maintain a good natural drift property, thereby failing to accurately attack an aimed fishing point.
Meanwhile, in order to reduce the length of the tapered section, it may be considered to be reasonable that the time required for varying an extrusion output of the vinylidene fluoride-based resin and a take-off speed of the obtained thread is shortened. However, the varying time is usually about one second. When the varying time is shortened to less than one second, it takes a long time to stabilize the extrusion output and the take-off speed, so that unevenness of thread tends be formed at the butt and tippet sections.
When the inherent viscosity exceeds 1.7 dl/g, there may be a tendency that an shape-unstable portion
6
(constriction) having a smaller diameter than an average diameter of the tippet section is generated at a connecting portion between the tapered section (B) and the tippet section (C), so that a stress is concentrated on the constricted portion upon fishing-up, thereby causing thread breakage of the leader. Besides, the melt fracture tends to be caused at the connecting portion, so that when the leader is stretched, thread breakage is likely to occur and the surface of the obtained leader is deteriorated in appearance.
The vinylidene fluoride-based resins may further contain a plasticizer, a heat stabilizer, an acrylic resin, a crystal nucleating agent, a lubricant or the like. Especially, in order to smoothly cast the leader or accurately drop the fly on the aimed fishing position, it is required that curl or kink of the leader reeled can be readily eliminated when unreeled. For this reason, it is preferred to add the plasticizer in an amount of 1 to 10% by weight.
As the plasticizers
Mizuno Toshiya
Nakano Eishou
Ohira Seiichi
Kureha Kagaku Kogyo Kabushiki Kaisha
Nixon & Vanderhye
Thomas Alexander S.
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