JP2001321324A - Flexible tube for endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible tube for an endoscope with excellent performances required or especially provide the flexible tube for the endoscope excellent in inserting performance, chemical resistance, and durability. SOLUTION: A flexible tube for an endoscope is composed of a spiral tube 21, a net tube 22 covering the outer circumference of the spiral tube 21, and a skin 3 covering the outer circumference of the net tube 22. The skin 3 is composed of lamination comprising an inner layer 31, an outer layer 32, and an intermediate layer 33. Thickness of the inner layer 31 is continuously and gradually decreased from a base end toward a tip. Thickness of the intermediate layer 33 is continuously and gradually decreased from the tip toward the base end, contrary to the inner layer 31. Total thickness of the inner layer 31 and the intermediate layer 33 is roughly constant along length. Thickness of the outer layer 32 is roughly constant along length. The intermediate layer 33 is composed of more flexible material than the inner layer 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible tube for an endoscope.

[0002]

2. Description of the Related Art A flexible tube for an endoscope has a structure in which a tubular core material in which the outer periphery of a spiral tube is covered with a mesh tube is covered with a sheath made of synthetic resin or the like.

In endoscopy, a flexible tube for an endoscope is inserted along a body cavity to a deep part of the body cavity such as the stomach, duodenum, small intestine or large intestine. In order to achieve good insertion operability at this time, the pushing force applied at the proximal end (hand side) of the flexible tube for an endoscope must be reliably transmitted to the distal end. Conversely, the endoscope tends to be in a state (buckling state) in which the pushing force applied on the proximal end side of the flexible tube for an endoscope is absorbed by the bent portion of the flexible tube for an endoscope. Flexible tube has poor insertion operability. In order to make the flexible tube for an endoscope hard to buckle, the flexible tube for an endoscope needs to have excellent elasticity to bending. In addition, since buckling is likely to occur at a portion where the outer skin has peeled off from the core material, the outer skin and the core material need to be in close contact with each other.

On the other hand, in order for the insertion operability to be good, when a twist (rotation) is applied on the proximal end side (hand side) of the flexible tube for an endoscope, this rotation is performed halfway. It is also necessary that the distal end be surely rotated along with the proximal end without being absorbed. For this reason, the flexible tube for an endoscope needs to be excellent in followability of the distal end portion to the rotation on the proximal end side.

Further, a flexible tube for an endoscope having a relatively high rigidity at the proximal end (hand side) and a flexible distal end is advantageous in terms of insertion operability, safety and reduction of the burden on the patient. It is said to be excellent.

Conventionally, as a flexible tube for an endoscope which has improved the operability of such insertion, the outer tube of the flexible tube for an endoscope has a two-layer structure of an outer layer and an inner layer, and the outer layer has flexibility. Good material,
The inner layer is made of a material having good resilience and considering the resilience (Japanese Patent Publication No. 5-50287), the distal side is made of a soft elastomer, the proximal side is made of a hard elastomer, and the distal side and the proximal side (Japanese Patent No. 264178)
No. 9).

However, in the prior art, since the adhesion (coupling force) between the outer skin and the core material is not taken into consideration, the outer skin is peeled off from the core material by repeated use, and the endoscope is flexibly used. The elasticity and buckling resistance of the pipe sometimes decreased. That is, there is a problem in durability of the flexible tube for an endoscope.

Further, the endoscope must be cleaned and disinfected each time it is used. In the prior art, since the chemical resistance of the outer skin is not taken into account, there is a risk that deterioration may progress due to repeated disinfection, fine cracks or the like may occur, or the outer skin may peel off from the core material.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a flexible tube for an endoscope having various performances required for a flexible tube for an endoscope. An object of the present invention is to provide a flexible tube for an endoscope excellent in chemical resistance and durability.

[0010]

This and other objects are achieved by the present invention which is defined below as (1) to (19).

(1) A flexible tube for an endoscope having a tubular core material and an outer skin coated on the outer periphery of the core material, wherein the outer skin is an inner layer, an outer layer, and a space between them. A portion formed of a laminate having at least one intermediate layer positioned therein, wherein at least one of the layers constituting the laminate has a thickness that varies along a longitudinal direction. A flexible tube for an endoscope, characterized by having a portion. Accordingly, it is possible to provide a flexible tube for an endoscope having excellent insertion operability, chemical resistance, and durability.

(2) The endoscope according to (1), wherein the thickness of the layer having the variable thickness portion changes continuously or stepwise over substantially the entire length of the laminate. Flexible tube. Thereby, the operability of the insertion is further improved.

(3) The flexible endoscope according to the above (1), wherein the layer having the variable thickness portion has a portion adjacent to the variable thickness portion and having a constant thickness. tube. Thereby, the operability of the insertion is further improved.

(4) Any one of the layers constituting the laminated body is made of a material having different physical characteristics or chemical characteristics from those of the other layers. The flexible tube for an endoscope according to any one of (1) to (3). Thereby, at least one of the operability, durability, and chemical resistance of insertion is further improved.

(5) The flexible tube for an endoscope according to the above (4), wherein the layer having the variable thickness portion is made of a material having a hardness different from that of any one of the other layers. Thereby, the operability of the insertion is further improved.

(6) The above (1) to (5), wherein two or more of the layers constituting the laminate have the variable thickness portion.
The flexible tube for an endoscope according to any one of the above. Thereby, the operability of the insertion is further improved.

(7) The flexible tube for an endoscope according to any one of the above (1) to (6), wherein the thickness of the laminate is substantially constant along the longitudinal direction. Thereby, the operability of insertion is further improved, and the burden on the patient is further reduced.

(8) The endoscope according to any one of the above (1) to (7), wherein the flexibility is continuously or gradually increased from the base end to the tip of the flexible tube for an endoscope. Flexible tube. Thereby, the operability of insertion is further improved, and the burden on the patient is further reduced.

(9) The flexible tube for an endoscope according to any one of the above (1) to (8), wherein the core material has a large number of holes and / or concave portions on an outer periphery thereof. Thereby, the operability and durability of the insertion are further improved.

(10) The core material includes a spiral tube formed by spirally winding a belt-like material, and a braided body formed by braiding a thin wire, which is coated on the outer periphery of the spiral tube and braided. The flexible tube for an endoscope according to (9). Thereby, the operability and durability of the insertion are further improved.

(11) The flexible tube for an endoscope according to the above (9) or (10), wherein a projection portion which has entered the hole and / or the concave portion of the core material is formed continuously from the inner layer. . Thereby, the operability and durability of the insertion are further improved.

(12) The flexible tube for an endoscope according to any one of the above (1) to (11), wherein the outer layer is made of a material having excellent chemical resistance. Thereby, chemical resistance is further improved.

(13) The flexible tube for an endoscope according to any one of the above (1) to (12), wherein the intermediate layer is a layer softer than the outer layer. Thereby, the operability of the insertion is further improved.

(14) The outer layer is a layer whose hardness is higher than the hardness of the inner layer and the intermediate layer.
The flexible tube for an endoscope according to any one of (13) to (13). Thereby, the operability of the insertion is further improved.

(15) The flexible tube for an endoscope according to any one of (1) to (14), wherein the intermediate layer has a cushioning function between the outer layer and the inner layer. Thereby, the operability and durability of the insertion are further improved.

(16) At least one of the inner layer, the outer layer, and the intermediate layer is made of a polyurethane elastomer, a polyester elastomer, a polyolefin elastomer, a polystyrene elastomer, a polyamide elastomer, a fluorine elastomer, and a fluorine rubber. The flexible tube for an endoscope according to any one of the above (1) to (15), comprising a material containing at least one selected from the group consisting of: Thereby, at least one of the operability, durability, and chemical resistance of insertion is further improved.

(17) The inner layer, the outer layer, and the intermediate layer are each selected from the group consisting of a polyurethane elastomer, a polyester elastomer, a polyolefin elastomer, a polystyrene elastomer, a polyamide elastomer, a fluorine elastomer, and a fluorine rubber. The flexible tube for an endoscope according to any one of the above (1) to (16), wherein the flexible tube is made of a material containing at least one of the above. Thereby, the operability of insertion, chemical resistance, and durability are further improved.

(18) The flexible tube for an endoscope according to any one of the above (1) to (17), wherein the outer cover is formed by coating the outer periphery of the core material by extrusion. Thereby, a flexible tube for an endoscope can be manufactured with good productivity and preferably.

(19) The thickness of the layer having the variable thickness portion is adjusted by adjusting the supply amount of the material forming the layer having the variable thickness portion and / or the moving speed of the core material in the extrusion molding. (18) The flexible tube for an endoscope according to the above (18). Thereby, a flexible tube for an endoscope can be manufactured with good productivity and preferably.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a flexible tube for an endoscope according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is an overall view showing an electronic endoscope (electronic scope) having an insertion portion flexible tube to which the flexible tube for an endoscope of the present invention is applied. Hereinafter, in FIG. 1, the upper side will be described as a “base end” and the lower side as a “distal end”.

As shown in FIG. 1, the electronic endoscope 10 includes a flexible (flexible) insertion section flexible tube 1a for a long object.
A bending tube 5 connected to the distal end 12 of the flexible tube 1a;
An operation unit 6 provided at the base end 11 of the insertion unit flexible tube 1a and operated by the operator to operate the entire electronic endoscope 10;
And a light source insertion portion 8 provided on the distal end side of the connection portion flexible tube 7.

The flexible insertion tube 1a is used by being inserted into a lumen of a living body. The operation unit 6 is provided with operation knobs 61 and 62 on its side surface. This operation knob 61,
By operating 62, the wire (not shown) provided in the insertion portion flexible tube 1a is pulled, and the bending tube 5 is bent in four directions, and the direction can be changed.

An image pickup device (CCD) (not shown) for picking up an image of a subject at an observation site is provided at the distal end of the bending tube 5, and an image signal connector 82 is provided at the distal end of the light source insertion section 8. Have been. The image signal connector 82 is connected to a light source processor (not shown),
Further, the light source processor device is connected to a monitor device (not shown) via a cable.

A light source connector 81 is provided at the end of the light source insertion portion 8, and the light source connector 81 is connected to a light source processor. The light emitted from the light source processor device is supplied to the light source connector 81, the light source insertion portion 8, the connection portion flexible tube 7, the operation portion 6, the insertion portion flexible tube 1a, and the bending tube 5. The light passes through a light guide (not shown) composed of optical fiber bundles arranged continuously, and is irradiated onto the observation site from the distal end of the curved tube 5 and illuminated.

The reflected light (subject image) from the observation site illuminated by the illumination light is picked up by an image pickup device. The image sensor outputs an image signal corresponding to the captured subject image.

The image signal is continuously arranged in the bending tube 5, the insertion portion flexible tube 1a, the operation portion 6, and the connection portion flexible tube 7, and the image sensor and the image signal connector 82 Is transmitted to the light source insertion unit 8 via an image signal cable (not shown) for connecting.

Then, predetermined processing (for example, signal processing, image processing, and the like) is performed in the light source insertion unit 8 and the light source processor device, and then input to the monitor device. In the monitor device, an image (electronic image) captured by the image sensor,
That is, an endoscope monitor image of a moving image is displayed.

The overall configuration of the electronic endoscope 10 having the flexible insertion tube 1a to which the flexible tube for an endoscope of the present invention is applied has been described above. It can also be applied to a flexible tube of a fiber endoscope,
Needless to say.

FIG. 2 is a longitudinal sectional view showing a first embodiment of an insertion portion flexible tube to which the flexible tube for an endoscope of the present invention is applied, and FIG.
3 is an enlarged semi-longitudinal cross-sectional view of the flexible tube 1a shown in FIG. 2 and 3, the right side is the base end 11 side (hand side),
The left side is the tip 12 side. In addition, in FIG.
And the illustration of the protrusion 4 are omitted (the same applies to FIGS. 4 to 7).

As shown in FIG. 3, the flexible tube 1a is
It has a core material 2 and an outer skin 3 covering the outer periphery thereof.
In addition, for example, a space 2 through which instruments such as optical fibers, electric wires, cables, tubes, and the like (omitted in the figure) can be disposed and inserted inside the flexible tube 1a.
4 are provided.

The core 2 is composed of a spiral tube 21 and a braided tube (braided body) 22 that covers the outer periphery of the spiral tube 21, and is formed as a tube-like long object as a whole. The core member 2 has an effect of reinforcing the insertion portion flexible tube 1a.
Particularly, by combining the spiral tube 21 and the mesh tube 22, the flexible tube 1a can secure sufficient mechanical strength. Although not shown, even higher strength can be obtained by arranging the helical tubes 21 twice or three times.

The spiral tube 21 is formed by spirally winding a belt-like material with a uniform diameter at an interval 25. As a material constituting the belt-like material, for example, stainless steel, a copper alloy, or the like is preferably used.

The braided tube 22 is formed by braiding a plurality of metal or non-metallic thin wires 23 arranged. As a material constituting the fine wire 23, for example, stainless steel, a copper alloy, or the like is preferably used. Also, the mesh tube 22
May be coated with a synthetic resin (not shown) on at least one of the fine wires 23 forming the pattern.

On the outer periphery of the braided tube 22, a braided thin wire 2
A gap 26 is formed by the third stitch. The gap 26 becomes a concave portion at a position overlapping the outer periphery of the spiral tube 21, and a hole communicating with the space 24 at a position overlapping the interval 25 of the spiral tube 21, and forms a large number of holes and concave portions on the outer periphery of the core material 2. are doing.

The outer periphery of the core material 2 is covered with an outer skin 3. The outer cover 3 is formed of a laminate having an inner layer 31, an outer layer 32, and an intermediate layer 33.

As will be described below, the outer skin 3 is
1, one of the outer layer 32 and the intermediate layer 33 is made of a material having different physical characteristics or chemical characteristics from those of the other one layer. Physical properties include, for example, rigidity (flexibility), hardness, elongation, tensile strength, shear strength, flexural modulus, flexural strength, and the like. Chemical properties include, for example, chemical resistance And weather resistance. Note that these are merely examples, and the present invention is not limited to these.

The inner layer 31 is formed on the innermost side of the outer skin 3 and is in close contact with the core material 2.

On the inner peripheral surface of the inner layer 31, a number of protrusions (anchors) 4 protruding toward the inner peripheral side are formed continuously from the inner layer 31. Each protruding portion 4 enters each of a large number of holes and concave portions formed on the outer periphery of the core material 2. The tip of the protrusion 4 that has entered the recess is a spiral tube 2
1 until it reaches the outer circumference. The protruding portion 4 that has entered the hole is formed longer, and its tip enters the space 25 of the spiral tube 21.

The inner layer 31 has a size (length) of the protrusion 4,
It is preferable that the projection 4 be formed of a material that can form the protruding portion 4 by controlling the shape, the number, and the like to be appropriate.

Since the projecting portion 4 is formed as described above, the projecting portion 4 engages with a large number of holes and recesses formed on the outer periphery of the core material 2, so that an anchor effect is generated, and The outer skin 3 is securely fixed with respect to. For this reason, even when the flexible tube 1 a of the insertion portion is curved, the outer skin 3 is kept in close contact with the core material 2, and expands and contracts sufficiently in accordance with the curvature of the core material 2. The restoring force of the outer skin 3 greatly expanded and contracted as described above is strongly exerted, and greatly contributes to the force for restoring the bending of the flexible tube 1a. Therefore, with such a configuration, the flexible insertion section tube 1a has high elasticity and excellent insertion operability.

Further, since the projecting portion 4 has a strong bonding force between the outer cover 3 and the braided tube 22, the outer cover 3 is hardly peeled off from the braided tube 22 even when used repeatedly. Therefore, the flexible tube 1a has good elasticity even after repeated use, and is excellent in durability.

When at least one of the thin wires 23 forming the mesh tube 22 is coated with a synthetic resin, at least a part of the coated resin (coating layer) is melted to form an inner layer. 31 (bonded).

By forming the constituent material of the inner layer 31 to include a material having excellent compatibility with the synthetic resin coated on the fine wire 23, the coating layer of the fine wire 23 is sufficiently bonded to the inner layer 31.

As described above, the coating layer of the fine wire 23 is
In the case where the outer shell 3 and the core material 2 are bonded together, the bonding strength between the outer skin 3 and the core material 2 is higher. In addition, the flexible tube 1a of the insertion portion has more excellent elasticity and durability.

The constituent material of the inner layer 31 is not particularly limited. For example, polyolefin such as polyvinyl chloride, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polyamide, polyethylene terephthalate (PE)
T), polyesters such as polybutylene terephthalate,
Polyurethane, polystyrene resin, polytetrafluoroethylene, fluorine-based resin such as ethylene-tetrafluoroethylene copolymer, various flexible resins such as polyimide, polyurethane-based elastomer, polyester-based elastomer, polyolefin-based elastomer, polyamide-based One or a combination of two or more of various elastomers such as an elastomer, a polystyrene-based elastomer, a fluorine-based elastomer, a silicone rubber, a fluorine rubber, and a latex rubber can be used.

Of these, polyurethane elastomers, polyolefin elastomers, and polyester elastomers are particularly easy to control the formation of the protruding portions 4.
preferable.

As shown in FIG. 2, the thickness of the inner layer 31 gradually decreases continuously from the base end 11 to the tip end 12.
In addition, a portion where the thickness of the inner layer 31 changes (variable thickness portion)
Extends over substantially the entire length of the outer skin 3. And the outer layer 32
The intermediate layer 33 has a substantially constant thickness along the longitudinal direction. Therefore, as the outer skin 3 is closer to the tip 12, the rigidity against tension, bending, and the like is smaller as the inner layer 31 is thinner.

As described above, since the rigidity of the outer cover 3 changes in the longitudinal direction, the flexibility of the insertion portion flexible tube 1a is changed from the proximal end 11 to the distal end 12 in most portions thereof. It increases continuously or stepwise. As a result, the insertion portion flexible tube 1a has sufficient rigidity in a portion near the base end 11, so that the pushing force and the rotating force from the hand are reliably transmitted to the tip 12, and in the portion near the tip 12, Since it is flexible, the distal end 12 smoothly advances to a curved body cavity, and the safety is high. Therefore, according to the insertion section flexible tube 1a, the operability of insertion is excellent and the burden on the patient is reduced.

In the intermediate portion between the base end 11 and the front end 12, the change in rigidity can be freely set by appropriately setting the rate of change of the thickness of the inner layer 31 along the longitudinal direction. This makes it possible to suitably realize various types of flexible tubes for endoscopes that match the examination site, the preferences of the operator, and the like.

The average thickness of the inner layer 31 (excluding the projection 4) is not particularly limited, but is usually 0.05 to
0.8 mm, preferably 0.05-0.4 mm
Is more preferable.

The thickness of the thinnest portion of the inner layer 31 is represented by T
1 _min, when the thickness of the thickest portion of the inner layer 31 was set to T1 _max, the value of the ratio T1 _min / T1 _max is not particularly limited, but is preferably 0.05 to 0.95, 0. 1
More preferably, it is 0.6.

The outer layer 32 is formed on the outermost side of the outer skin 3. The outer layer 32 is preferably made of a material having chemical resistance. Thereby, even if the washing and disinfection are repeatedly performed, the outer skin 3 is hardly deteriorated, and the outer skin 3 hardens, and the flexibility is reduced, and the outer skin 3 is hardly peeled off from the mesh tube 22 due to cracks or the like.

The hardness of the outer layer 32 is set relatively high. The hardness of the outer layer 32 is preferably higher than the hardness of the inner layer 31 and the intermediate layer 33. Thereby, even if it is repeatedly used, the surface of the outer cover 3 is not easily scratched, and is less likely to cause a crack or the like.

Here, usually, when the hardness of the outer layer 32 is made relatively high in consideration of chemical resistance and resistance to scratching, the flexibility and elasticity of the insertion portion flexible tube 1a decrease. There is a possibility that. On the other hand, in the present invention, there is no such a possibility by providing the flexible intermediate layer 33 as described later.

The constituent material of the outer layer 32 is not particularly limited. For example, polyolefin such as polyvinyl chloride, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polyamide, polyethylene terephthalate (PE)
T), polyesters such as polybutylene terephthalate,
Polyurethane, polystyrene resin, polytetrafluoroethylene, fluorine-based resin such as ethylene-tetrafluoroethylene copolymer, various flexible resins such as polyimide, polyurethane-based elastomer, polyester-based elastomer, polyolefin-based elastomer, polyamide-based One or a combination of two or more of various elastomers such as an elastomer, a polystyrene-based elastomer, a fluorine-based elastomer, a silicone rubber, a fluorine rubber, and a latex rubber can be used.

Among them, in particular, polyolefins such as ethylene-vinyl acetate copolymer, fluorine resins such as polytetrafluoroethylene and ethylene-tetrafluoroethylene copolymer, polyester elastomers, polyolefin elastomers, fluorine elastomers, Silicone rubber and fluoro rubber are preferable because of their excellent chemical resistance.

The average thickness of the outer layer 32 is not particularly limited, but is usually preferably 0.05 to 0.8 mm, more preferably 0.05 to 0.4 mm.

The intermediate layer 33 is formed between the inner layer 31 and the outer layer 32. It is preferable that the intermediate layer 33 be a layer that is more flexible (excellent in elasticity) than the outer layer 32. Thus, the intermediate layer 33 exhibits a cushion function between the inner layer 31 and the outer layer 32. Further, the intermediate layer 33 includes the inner layer 31.
Preferably, the layer is more flexible.

The cushion function of the intermediate layer 33 will be described in more detail. When the flexible tube 1a is bent, the elasticity of the intermediate layer 33 is excellent, so that the deformed intermediate layer 33 exerts a strong restoring force. Since the intermediate layer 33 is sandwiched between the inner layer 31 and the outer layer 32 having relatively high hardness, the restoring force of the intermediate layer 33 is efficiently transmitted to the inner layer 31 and the outer layer 32. Therefore, almost all of the restoring force of the intermediate layer 33 is used for restoring the bending of the flexible tube 1a. Therefore, by adopting such a configuration, the insertion portion flexible tube 1a is excellent in elasticity.

The constituent material of the intermediate layer 33 is not particularly limited. For example, polyolefin such as polyvinyl chloride, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polyamide, polyethylene terephthalate (P
ET), polyesters such as polybutylene terephthalate, polyurethanes, polystyrene resins, polytetrafluoroethylene, fluorine resins such as ethylene-tetrafluoroethylene copolymer, various flexible resins such as polyimides, polyurethane elastomers, Among various elastomers such as polyester elastomer, polyolefin elastomer, polyamide elastomer, polystyrene elastomer, fluorine elastomer, silicone rubber, fluorine rubber, latex rubber, etc.
Species or a combination of two or more can be used.

Among these, polyurethane elastomers, polyolefin elastomers, and polyester elastomers having low hardness are particularly preferred because of their excellent flexibility (elasticity).

In the present embodiment, the intermediate layer 33 has a single-layer configuration, but may have a configuration in which two or more intermediate layers 33 are formed.

The average thickness of the intermediate layer 33 is not particularly limited, but is usually preferably from 0.05 to 0.8 mm, and more preferably from 0.05 to 0.4 mm.

The average thickness of the entire outer skin 3 (excluding the protruding portion 4) can protect the core material 2 and instruments and the like inserted therein from liquids such as body fluids, and can be inserted. There is no particular limitation as long as the curveability of the flexible tube 1a is not hindered. Usually, it is preferably 0.15 to 0.9 mm, and more preferably 0.3 to 0.8 mm.

The method for manufacturing the flexible tube for an endoscope as described above is not particularly limited, but it can be manufactured continuously by coating the core 3 with the core 2 by extrusion molding. According to the extruder having a plurality of extrusion ports, the inner layer 31, the outer layer 32 and the intermediate layer 33 are simultaneously extruded,
The laminate can be coated on the core material 2. In addition, by adjusting the supply amount (the supply amount per unit time) of the constituent material of each layer and the moving speed of the core material 2 from each extrusion port,
The thickness of each layer can be adjusted.

The material temperature during extrusion molding is not particularly limited, but is preferably, for example, about 130 to 220 ° C., and more preferably about 165 to 205 ° C. If the material temperature during extrusion is in such a temperature range,
The material is excellent in formability of the outer cover 3. Therefore, the uniformity of the thickness of the outer cover 3 is improved.

FIG. 4 is a longitudinal sectional view showing a second embodiment of an insertion portion flexible tube to which the flexible tube for an endoscope of the present invention is applied.
In FIG. 4, the right side is the proximal end 11 side (hand side), and the left side is the distal end 12 side.
Side. Hereinafter, a second embodiment of the flexible tube for an endoscope according to the present invention will be described, but the description will focus on differences from the first embodiment described above, and description of similar items will be omitted.

In the flexible tube 1b shown in FIG.
In addition to the fact that the thickness of the inner layer 31 of the outer cover 3 is changed in the same manner as the insertion portion flexible tube 1a in the first embodiment described above,
The thickness of the intermediate layer 33 also changes in the longitudinal direction.

The thickness of the intermediate layer 33 is gradually reduced from the distal end 12 to the proximal end 11, as opposed to the inner layer 31.
In addition, the variable thickness portion in which the thickness of the intermediate layer 33 changes extends over substantially the entire length of the outer cover 3. Then, the inner layer 31 and the intermediate layer 33
Is substantially constant along the longitudinal direction. The thickness of the outer layer 32 is substantially constant along the longitudinal direction.

The thickness of the thinnest part of the intermediate layer 33 is represented by T3
_min, when the thickness of the thickest portion of the intermediate layer 33 was set to T3 _max, the value of the ratio T3 _min / T3 _max is not particularly limited, but is preferably 0.05 to 0.95, 0. 1
More preferably, it is 0.6. Also, the intermediate layer 33
Is made of a material that is more flexible than the inner layer 31.

With such a configuration, the outer cover 3 has a substantially constant thickness (excluding the protruding portion 4) along the longitudinal direction. Since the proportion occupied by the layer 33 increases, the rigidity against tension and bending is small.

Due to such a change in the rigidity of the outer cover 3 along the longitudinal direction, the flexible portion of the insertion portion flexible tube 1a has its flexibility continuously or stepwise from the proximal end 11 to the distal end 12 in most portions thereof. Is higher. Thus, the insertion section flexible tube 1b is excellent in insertion operability similarly to the insertion section flexible tube 1a of the first embodiment.

Further, by gradually reducing the thickness of the intermediate layer 33 toward the base end 12, the entire outer diameter of the flexible tube 1b is substantially constant. In other words, the outer diameter of the portion near the base end 12 is reduced. Therefore, the burden on the patient can be further reduced.

FIG. 5 is a longitudinal sectional view showing a third embodiment of an insertion portion flexible tube to which the flexible tube for an endoscope of the present invention is applied.
In FIG. 5, the right side is the proximal end 11 side (hand side), and the left side is the distal end 12 side.
Side. Hereinafter, a third embodiment of the flexible tube for an endoscope according to the present invention will be described, but the description will focus on differences from the above-described first embodiment, and description of similar items will be omitted.

In the insertion portion flexible tube 1c shown in FIG.
The inner layer 31 and the intermediate layer 33 have a variable thickness portion.
These variable thickness portions 34 are formed on a part of the entire length of the outer cover 3. The length of the variable thickness portion 34 is relatively short, for example, about 5 to 80 mm. The thickness of the outer layer 32 is substantially constant along the longitudinal direction.

The thickness of the inner layer 31 is determined by
And gradually decreases toward the tip 12. On the proximal end 11 side and the distal end 12 side of the variable thickness portion 34, the thickness of the inner layer 31 is:
It is almost constant. Therefore, the thickness of the inner layer 31 closer to the base end 11 than the variable thickness portion 34 is smaller than that of the inner layer 31
It is thicker than the thickness of the inner layer 31 on the side.

The thickness of the intermediate layer 33 is set at the base end 1 at the variable thickness portion 34.
It gradually increases from 1 to the tip 12. On the base end 11 side and the tip end 12 side of the variable thickness portion 34, the thickness of the intermediate layer 33 is substantially constant. Therefore, the thickness of the intermediate layer 33 on the base end 11 side of the variable thickness portion 34 is smaller than the thickness of the intermediate layer 33 on the distal end 12 side of the variable thickness portion 34.

Thickened portion 34 of inner layer 31 and intermediate layer 33
Are formed at the same position in the longitudinal direction, and the total thickness of the inner layer 31 and the intermediate layer 33 includes the variable thickness portion 34,
It is constant along the longitudinal direction. Also, the intermediate layer 33
Is made of a material that is more flexible than the inner layer 31.

With such a configuration, the outer cover 3 has a relatively high rigidity at the base end 11 side of the thickened portion 34 and the thickened portion 3
4 has relatively low rigidity on the side of the distal end 12, and the rigidity of the variable thickness portion 34 is intermediate between them and changes in the longitudinal direction.

Due to such a change in the rigidity of the outer cover 3 in the longitudinal direction, the flexible tube 1 c of the insertion portion is moved from the thicker portion 34 to the proximal end 11.
The side has sufficient rigidity, and is more flexible on the tip 12 side than the variable thickness portion 34. Therefore, excellent insertion operability can be obtained also by such an insertion portion flexible tube 1c. In addition, the thickness of the outer cover 3 is substantially constant along the longitudinal direction,
The outer diameter of the insertion portion flexible tube 1c can be made substantially constant,
The burden on the patient can be further reduced.

Further, by forming such a thickened portion 34 at a plurality of places or by forming the thickened portion 34 much longer than in the present embodiment, the flexibility is increased stepwise or substantially along the longitudinal direction. It may be changed continuously.

FIG. 6 is a longitudinal sectional view showing a fourth embodiment of an insertion portion flexible tube to which the flexible tube for an endoscope of the present invention is applied.
In FIG. 6, the right side is the proximal end 11 side (hand side), and the left side is the distal end 12.
Side. Hereinafter, a fourth embodiment of the flexible tube for an endoscope according to the present invention will be described, but the description will focus on differences from the first embodiment described above, and description of similar items will be omitted.

In the insertion portion flexible tube 1d shown in FIG.
The thicknesses of the outer layer 32 and the intermediate layer 33 change in the longitudinal direction. The thickness of the inner layer 31 is substantially constant along the longitudinal direction.

The thickness of the outer layer 32 ranges from the proximal end 11 to the distal end 12.
It gradually decreases toward. The variable thickness portion where the thickness of the outer layer 32 changes extends over substantially the entire length of the insertion portion flexible tube 1d.

The thickness of the thinnest portion of the outer layer 32 is represented by T
When 2 _min, the thickness of the thickest portion of the outer layer 32 was set to T2 _max, the value of the ratio T2 _min / T2 _max is not particularly limited, but is preferably 0.05 to 0.95, 0. 1
More preferably, it is 0.6.

The thickness of the intermediate layer 33 continuously decreases from the distal end 12 to the proximal end 11, as opposed to the outer layer 32.
Further, the variable thickness portion in which the thickness of the intermediate layer 33 changes extends over substantially the entire length of the insertion portion flexible tube 1d. The total thickness of the outer layer 32 and the intermediate layer 33 is substantially constant along the longitudinal direction. The intermediate layer 33 is made of a material that is more flexible than the outer layer 32.

That is, the flexible insertion tube 1d corresponds to the flexible insertion tube 1b of the second embodiment in which the thickness of the outer layer 32 is changed instead of the inner layer 31. Therefore, according to such an insertion portion flexible tube 1d, the same operation and effect as the insertion portion flexible tube 1b of the second embodiment can be obtained.

FIG. 7 is a longitudinal sectional view showing a fifth embodiment of an insertion portion flexible tube to which the flexible tube for an endoscope of the present invention is applied.
7, the right side is the proximal end 11 side (hand side), and the left side is the distal end 12 side.
Side. Hereinafter, a fifth embodiment of the flexible tube for an endoscope according to the present invention will be described, but the description will focus on differences from the above-described first embodiment, and description of similar items will be omitted.

In the flexible tube 1e shown in FIG.
The outer layer 32 and the intermediate layer 33 have a variable thickness portion.
These variable thickness portions 34 are formed on a part of the entire length of the outer cover 3. The length in the longitudinal direction of the variable thickness portion 34 is, for example, 5 to 8
It is relatively short, about 0 mm. The thickness of the inner layer 31 is substantially constant along the longitudinal direction.

The thickness of the outer layer 32 is adjusted at
And gradually decreases toward the tip 12. On the proximal end 11 side and the distal end 12 side from the variable thickness portion 34, the thickness of the outer layer 32 is
It is almost constant. Therefore, the thickness of the outer layer 32 closer to the base end 11 than the variable thickness portion 34 is smaller than the thickness of the outer layer 32
It is thicker than the thickness of the outer layer 32 on the side.

The thickness of the intermediate layer 33 is set at the base end 1 at the variable thickness portion 34.
It gradually increases from 1 to the tip 12. On the base end 11 side and the tip end 12 side of the variable thickness portion 34, the thickness of the intermediate layer 33 is substantially constant. Therefore, the thickness of the intermediate layer 33 on the base end 11 side of the variable thickness portion 34 is smaller than the thickness of the intermediate layer 33 on the distal end 12 side of the variable thickness portion 34.

The thickness change portion 34 of the outer layer 32 and the intermediate layer 33
Are formed at the same position in the longitudinal direction, and the total thickness of the outer layer 32 and the intermediate layer 33 includes the variable thickness portion 34,
It is almost constant along the longitudinal direction. The intermediate layer 33 is made of a material that is more flexible than the outer layer 32.

That is, the flexible insertion tube 1e corresponds to the flexible insertion tube 1c of the third embodiment in which the thickness of the outer layer 32 is changed instead of the inner layer 31. Therefore, according to such an insertion portion flexible tube 1e, the same operation and effect as those of the insertion portion flexible tube 1c in the third embodiment can be obtained.

As described in each of the above embodiments, the flexible tube for an endoscope of the present invention comprises the inner layer 31, the outer layer 32 and the intermediate layer 33 over the entire length of the laminate constituting the outer skin 3. Have. Further, it is not necessary to change the composition of the material constituting each of these layers along the longitudinal direction. Therefore, the characteristics of each layer of the laminate do not differ between the portions of the laminate, and are provided over the entire length of the laminate.
Therefore, the adhesiveness of the inner layer 31 to the core material 2, the chemical resistance of the outer layer 32, and the flexibility of the intermediate layer 33 can be improved over the entire length of the laminate. Thereby, the durability, chemical resistance, and elasticity of the flexible tube for an endoscope can be improved over the entire length of the laminate.
As described above, according to the present invention, a change in rigidity (flexibility) along the longitudinal direction is imparted to the flexible tube for an endoscope while maintaining various excellent characteristics over the entire length of the laminate. can do.

Although the flexible tube for an endoscope of the present invention has been described above, the present invention is not limited to these.

For example, the layer having the variable thickness portion is not limited to that described in the embodiment, and only the outer layer 32 and the intermediate layer 3
3, only the inner layer 31 and the outer layer 32, or all the layers constituting the laminate may have a variable thickness portion.

As a method of manufacturing a flexible tube for an endoscope, first, the outer cover 3 is formed as a continuous long object,
A method is also possible in which the core material 2 is inserted into the inner cavity of the outer skin 3 and then tightly fixed by heating or the like.

The outer tube of the flexible tube for an endoscope according to the present invention is not limited to the one whose outer skin is constituted by the above-described laminated body over its entire length, and the outer skin is partially formed in the longitudinal direction as described above. It may be composed of a laminate having the above configuration.

Further, the flexible tube for an endoscope of the present invention can be applied to, for example, a light guide flexible tube.

[0111]

The present invention will now be described by way of Examples and Comparative Examples.
This will be described in more detail.

1. Production of Flexible Tube for Endoscope (Example 1) First, a stainless steel strip having a width of 3 mm was wound to produce a spiral tube 21 having an outer diameter of 9.9 mm and an inner diameter of 9.6 mm. Next, a braided tube 22 was prepared by braiding the ten thin stainless steel wires 23 each having a diameter of 0.1 mm. One of the fine wires 23 was coated with a polyamide resin. This mesh tube 2
2 was used to cover the helical tube 21 to obtain a core material 2.

Next, the outer periphery of the core material 2 is formed by extrusion molding.
An outer skin 3 composed of three layers of an inner layer 31, an outer layer 32, and an intermediate layer 33 was covered to produce a 1.6 m long flexible tube for an endoscope.

The thickness of the inner layer 31 is set at 0.1 at the tip 12.
05 mm (T1 _min ), 0.4 mm at base end 11
(T1 _max ), and gradually increased from the distal end 12 to the proximal end 11 at a constant rate. From these, T1 _min / T1
_max is 0.125. The thickness of the outer layer 32 was 0.1 mm over the entire length of the flexible tube for an endoscope.

The thickness of the intermediate layer 33 is 0.4 mm (T3 _max ) at the front end 12 and 0.05 m at the base end 11.
m (T3 _min ), and gradually decreased at a constant rate from the distal end 12 to the proximal end 11. From these, T3 _min / T
3 _max is 0.125. Table 1 shows constituent materials of each layer of the outer cover 3 in the flexible tube for an endoscope of Example 1.

(Example 2) A flexible tube for an endoscope was produced in the same manner as in Example 1 except that the thickness of each layer of the outer cover 3 was changed as follows. The thickness of the inner layer 31 was set to 0.1 mm over the entire length of the flexible tube for an endoscope.

The thickness of the outer layer 32 is set at 0.1 at the tip 12.
05 mm (T2 _min ), 0.4 mm at base end 11
(T2 _max ), and gradually increased from the distal end 12 to the proximal end 11 at a constant rate. From these, T2 _min / T2
_max is 0.125.

The thickness of the intermediate layer 33 is 0.4 mm (T3 _max ) at the front end 12 and 0.05 m at the base end 11.
m (T3 _min ), and gradually decreased at a constant rate from the distal end 12 to the proximal end 11. From these, T3 _min / T
3 _max is 0.125. Table 1 shows constituent materials of each layer of the outer cover 3 in the flexible tube for an endoscope of Example 2.

(Example 3) A flexible tube for an endoscope was produced in the same manner as in Example 1 except that the thickness of each layer of the outer cover 3 was changed as follows.

The entire length of the flexible tube for an endoscope is divided into four equal parts, and the tip 1
From 2 to the base end 11, it was sequentially divided into first to fourth regions.
The thickness of the inner layer 31 was 0.1 mm over all of the first to fourth regions.

The thickness of the outer layer 32 is set to 0.05 in the first region.
mm (T2 _min ), the second area is 0.15 mm, the third area is 0.25 mm, and the fourth area is 0.4 mm (T2 _min ).
_max ). From these, T2 _min / T2 _max is set to 0.
125.

The thickness of the intermediate layer 33 is set so that the first region has a thickness of 0.4.
mm (T3 _max ), the second region is 0.25 mm, the third region is 0.15 mm, and the fourth region is 0.05 mm (T3 _max ).
_min ). From these, T3 _min / T3 _max is set to 0.
125.

At the boundary of each region, a variable thickness portion 34, which is very short compared to the entire length of the flexible tube for an endoscope, was formed. Table 1 shows constituent materials of each layer of the outer cover 3 in the flexible tube for an endoscope of the third embodiment.

(Example 4) A flexible tube for an endoscope was manufactured in the same manner as in Example 2 except that the material and thickness of the outer layer 32 were changed.

[0125] The thickness of the outer layer 32 is
1 mm (T2 _min ), 0.45 mm at base end 11
(T2 _max ), and gradually increased from the distal end 12 to the proximal end 11 at a constant rate. From these, T2 _min / T2
_max is 0.222. Table 1 shows constituent materials of each layer of the outer cover 3 in the flexible tube for an endoscope of Example 4.

Example 5 A flexible tube for an endoscope was manufactured in the same manner as in Example 1 except that the material of the outer layer 32 was changed. Table 1 shows constituent materials of each layer of the outer cover 3 in the flexible tube for an endoscope of Example 5.

The longitudinal sections of the flexible tubes for endoscopes of Examples 1 to 5 were as shown in FIG. 3 (however, the thickness of each layer was the thickness set in each Example). Was.)

(Comparative Examples 1 to 3) Core 2 similar to that of Example 1
Of the inner layer 31 and the outer layer 32 by extrusion molding
A flexible tube for an endoscope having a length of 1.6 m was produced by coating the outer skin composed of the layers. The thickness of the inner layer 31 and the outer layer 32 is constant over the entire length of the flexible tube for an endoscope.
The outer layer 32 was 2 mm, and the outer layer 32 was 0.3 mm.

Table 1 shows the constituent materials of each layer of the outer cover 3 in the flexible tubes for endoscopes of Comparative Examples 1 to 3.

[0130]

[Table 1]

Materials A to D in Table 1 are as follows.
Material A: Medium hardness polyurethane elastomer (JIS
81) Material B: Low hardness polyurethane elastomer (JIS)
Hardness according to K 7311 68) Material C: High hardness polyester elastomer (JIS
Hardness according to K 7311 92) Material D: High hardness polyolefin-based elastomer (JIS
Material E: High hardness polyurethane-based elastomer (JIS)
Hardness according to K 7311 92)

Observation of the longitudinal section of the flexible tube for an endoscope of each comparative example shows that the comparative examples 1 and 2 show the first embodiment.
5, the protrusions 4 were formed as shown in FIG. 3, but in Comparative Example 3, the protrusions 4 were not formed.

<Measurement of Bending Stiffness Change Ratio> Examples 1 to 5
The rate at which the bending stiffness of the flexible tube for an endoscope changes along the longitudinal direction was measured.

Here, the entire length of the flexible tube for an endoscope is divided into eight equal parts, and sequentially divided into first to eighth regions from the distal end 12 to the proximal end 11. Was measured by the following method.

As shown in FIG. 8, a fixed span L (20
0 mm), the midpoint of each area is supported at the center of the span, and the midpoint of each area is pressed downward to push the point when the pressed point is displaced by a certain distance y (50 mm). The magnitude of the pressure F was defined as the bending rigidity in each region.

When the bending stiffness in the first region is set to 1, the magnitude of the bending stiffness in each of the other regions is represented by:
The rate of change in bending stiffness along the longitudinal direction was examined. Table 2 shows the rate of change of the bending stiffness for each flexible tube for an endoscope.

[0137]

[Table 2]

[0138] 2. Evaluation of characteristics of flexible tube for endoscope [2.1] Operability test for insertion For each flexible tube for endoscope produced in each of Examples and Comparative Examples, an operability test for insertion was performed.

The electronic endoscope 10 shown in FIG. 1 was manufactured by using each endoscope flexible tube as the insertion portion flexible tube. The insertion portion of each manufactured electronic endoscope 10 was inserted into a biological model imitating a body cavity of a human body, and was inserted until its tip (the tip of the curved tube 5) reached a portion corresponding to the large intestine of the biological model. In the insertion operability test, the insertion operability at that time was evaluated according to the following four-grade criteria. ◎: The insertion operation can be performed very smoothly, and is optimal for use as a flexible tube for an endoscope. ：: The insertion operation can be performed without any trouble, and it is suitable for use as a flexible tube for an endoscope. Δ: Troublesome insertion operation and problematic use as flexible tube for endoscope. X: The insertion operation is difficult and not suitable for use as a flexible tube for an endoscope. Table 3 shows the results of the insertion operability test.

[2.2] Chemical resistance test A chemical resistance test was performed on each flexible tube for an endoscope produced in each of the examples and comparative examples.

The flexible tube for an endoscope produced in each of the examples and comparative examples was placed in a 10% iodine aqueous solution 1 maintained at 25 ° C.
Each was immersed in 00L for 200 hours.

In the chemical resistance test, two flexible tubes for each endoscope were used.
The state after 00 hours was evaluated according to the following four-grade criteria. A: No change in appearance. No cracking and lifting of the hull. ：: Almost no change in appearance. Slight lifting of outer skin. Δ: It can be seen that the appearance was deteriorated. Floating of outer skin occurs in various places. ×: Deterioration of appearance can be clearly recognized. Cracks and lifting of the outer skin occurred remarkably. Table 3 shows the results of the chemical resistance test.

[2.3] Durability Test A durability test was performed on each flexible tube for an endoscope produced in each of the examples and comparative examples.

The durability is evaluated based on the degree of decrease in elasticity before and after the bending operation after repeating the operation of bending the 90 ° bending at 90 ° while supporting both ends of each endoscope flexible tube. The evaluation was performed according to the following four criteria. ：: The elasticity was hardly changed, and the durability was very excellent. ：: The elasticity is slightly reduced and the durability is excellent. Δ: The elasticity was reduced as clearly seen, and there was a problem in durability. X: The elasticity was remarkably reduced, and deterioration was confirmed at various places. Table 3 shows the results of the durability test.

[0145]

[Table 3]

From the results shown in Table 3, it was clarified that the flexible tubes for endoscopes of the respective examples were excellent in all of the operability of insertion, chemical resistance and durability.

On the other hand, the flexible tube for an endoscope of Comparative Example 1 was slightly inferior in insertion operability and inferior in chemical resistance, probably due to poor chemical resistance of the outer layer material.

The flexible tube for an endoscope of Comparative Example 2 was inferior in insertion operability. In addition, the flexible tube for an endoscope of Comparative Example 3 was inferior in insertion operability, and inferior in durability because the protruding portion 4 was not formed in the inner layer 31.

[0149]

As described above, according to the present invention, in each layer of the laminated body constituting the outer skin, selection of a material, setting of thickness, etc. are appropriately performed, and an endoscope is obtained by combining the characteristics of each layer. Various performances required for the flexible tube for a mirror can be simultaneously improved.

In particular, by appropriately changing the thickness of at least one of the layers constituting the laminate in the longitudinal direction, a flexible tube for an endoscope excellent in operability of insertion can be obtained.

Further, by using a flexible material for the intermediate layer, the elasticity of the flexible tube for an endoscope is excellent, and the operability of insertion is more excellent.

Further, by selecting the material of the outer layer, it is possible to make the flexible tube for an endoscope excellent in chemical resistance.

Further, by using a material having high adhesion to the core material for the inner layer, the flexible tube for an endoscope can be made excellent in durability.

Further, as described above, it is possible to provide these excellent performances.

[Brief description of the drawings]

FIG. 1 is an overall view showing an electronic endoscope having an insertion portion flexible tube to which the endoscope flexible tube of the present invention is applied.

FIG. 2 is a longitudinal sectional view showing a first embodiment of an insertion portion flexible tube to which the flexible tube for an endoscope of the present invention is applied.

FIG. 3 is an enlarged semi-longitudinal sectional view of the flexible tube of the insertion portion shown in FIG. 2;

FIG. 4 is a longitudinal sectional view showing a second embodiment of an insertion portion flexible tube to which the flexible tube for an endoscope of the present invention is applied.

FIG. 5 is a longitudinal sectional view showing a third embodiment of an insertion portion flexible tube to which the flexible tube for an endoscope of the present invention is applied.

FIG. 6 is a longitudinal sectional view showing a fourth embodiment of an insertion portion flexible tube to which the flexible tube for an endoscope of the present invention is applied.

FIG. 7 is a longitudinal sectional view showing a fifth embodiment of an insertion portion flexible tube to which the flexible tube for an endoscope of the present invention is applied.

FIG. 8 is a diagram showing a method for measuring the bending stiffness of the flexible tube of the insertion portion in the embodiment.

[Explanation of symbols]

 1a, 1b, 1c, 1d, 1e Flexible tube for insertion portion 11 Base end 12 Tip 2 Core material 21 Spiral tube 22 Reticulated tube 23 Fine wire 24 Space 25 Spacing 26 Gap 3 Outer skin 31 Inner layer 32 Outer layer 33 Intermediate layer 34 Thickened section 4 Projecting portion 5 Bending tube 6 Operating portion 61, 62 Operating knob 7 Flexible connecting portion 8 Light source insertion portion 81 Light source connector 82 Image signal connector 10 Electronic endoscope

Continued on the front page (72) Inventor Hideo Namba 2-36-9 Maenocho, Itabashi-ku, Tokyo Asahi Gaku Kogyo Co., Ltd. (72) Inventor Masaru Takeshige 2-36-9 Maenocho, Itabashi-ku, Tokyo Asahi F-term in Gaku Kogyo Co., Ltd. (Reference) 2H040 AA01 BA00 DA16 3H111 AA02 CA52 CA57 CB21 DB27 4C061 DD03 FF25 FF26 FF27 JJ03 JJ06 JJ11

Claims (19)

[Claims] 1. A flexible tube for an endoscope having a tubular core material and an outer skin coated on the outer periphery of the core material, wherein the outer skin is positioned between an inner layer, an outer layer, and the outer layer. A portion formed of a laminate having at least one intermediate layer, wherein at least one of the layers constituting the laminate has a variable thickness portion whose thickness changes along a longitudinal direction. A flexible tube for an endoscope, characterized by having: 2. The flexible endoscope according to claim 1, wherein the thickness of the layer having the variable thickness portion changes continuously or stepwise over substantially the entire length of the laminate. tube. 3. The flexible tube for an endoscope according to claim 1, wherein the layer having the variable thickness portion has a portion adjacent to the variable thickness portion and having a constant thickness. 4. A method according to claim 1, wherein one of the layers constituting the laminate is made of a material having different physical characteristics or chemical characteristics from those of the other layers. The flexible tube for an endoscope according to any one of the above. 5. The flexible tube for an endoscope according to claim 4, wherein the layer having the variable thickness portion is made of a material having a hardness different from any one of the other layers. 6. The flexible tube for an endoscope according to claim 1, wherein at least two of the layers constituting the laminate have the variable thickness portion. 7. The flexible tube for an endoscope according to claim 1, wherein the thickness of the laminate is substantially constant along a longitudinal direction. 8. The flexible tube for an endoscope according to claim 1, wherein the flexibility increases continuously or stepwise from a base end to a distal end of the flexible tube for an endoscope. . 9. The flexible tube for an endoscope according to claim 1, wherein the core material has a large number of holes and / or concave portions on an outer periphery thereof. 10. The core material includes: a spiral tube formed by spirally winding a band-shaped material; and a braided body which is formed by braiding a thin wire which is coated on the outer periphery of the spiral tube and braided. 10. The flexible tube for an endoscope according to 9. 11. The flexible tube for an endoscope according to claim 9, wherein a protruding portion which has entered the hole and / or the concave portion of the core material is formed continuously from the inner layer. 12. The flexible tube for an endoscope according to claim 1, wherein the outer layer is made of a material having excellent chemical resistance. 13. The flexible tube for an endoscope according to claim 1, wherein the intermediate layer is a layer that is more flexible than the outer layer. 14. The outer layer is a layer whose hardness is higher than the hardness of the inner layer and the intermediate layer.
4. The flexible tube for an endoscope according to any one of 3. 15. The flexible tube for an endoscope according to claim 1, wherein the intermediate layer has a cushion function between the outer layer and the inner layer. 16. At least one of the inner layer, the outer layer, and the intermediate layer comprises a polyurethane elastomer, a polyester elastomer, a polyolefin elastomer, a polystyrene elastomer, a polyamide elastomer, a fluorine elastomer, and a fluorine rubber. The flexible tube for an endoscope according to any one of claims 1 to 15, wherein the flexible tube is made of a material containing at least one selected from the group. 17. The method according to claim 17, wherein the inner layer, the outer layer, and the intermediate layer are a polyurethane-based elastomer, a polyester-based elastomer, and a polyolefin-based elastomer, respectively.
17. The flexible tube for an endoscope according to claim 1, wherein the flexible tube is made of a material containing at least one selected from the group consisting of a polystyrene elastomer, a polyamide elastomer, a fluorine elastomer, and a fluorine rubber. . 18. The flexible tube for an endoscope according to claim 1, wherein the outer cover is formed by coating an outer periphery of the core material by extrusion molding. 19. The thickness of the layer having the variable thickness portion is adjusted by adjusting the supply amount of a material constituting the layer having the variable thickness portion and / or the moving speed of the core material in the extrusion molding. The flexible tube for an endoscope according to claim 18, wherein