Endoscope

1. An endoscope including a bending portion in an insertion portion, comprising:

first and second pulling members mounted on the bending portion;

a bending operation knob for generating a driving force for pulling the pulling members in conjunction with a turning operation and bending the bending portion between an approximately straight state and a bending state;

a driving force transfer mechanism for transferring the driving force generated in conjunction with the turning operation of the bending operation knob to one of the first and second pulling members mounted on the bending portion;

a biasing mechanism including:

a coil spring which is a push spring provided approximately in parallel with a moving direction of the pulling members;

a fixing member for integrally fixing a side of one end face of the coil spring on an operation portion;

a sliding member placed separately from and opposite an other end face of the coil spring; and

an arm portion forming member for integrally connecting the sliding member to a predetermined position of a connecting member connected to the driving force transfer mechanism which is moved in conjunction with a turning operation of the bending operation knob, when the bending portion is bent by turning the bending operation knob and pulling the first pulling member, the biasing mechanism being adapted for providing a biasing force for turning the bending operation knob in a reverse direction to a direction of the turning operation by the sliding member being moved with movement of the driving force transfer mechanism and contacting the other end face of the coil spring, in a state where the bending portion is bent by turning the bending operation knob and pulling the first pulling member of the first and second pulling members; and

a connection member axially connecting the driving force transfer mechanism to the one of the first pulling member and the second pulling member, wherein the connection member comprises mounting holes for receiving the arm portion forming member;

wherein the push spring imparts a compressive force to the sliding member for biasing the bending portion from the bending state to the approximately straight state.

2. The endoscope according to claim 1 , wherein:

in a state where the bending operation knob is turned,

the biasing mechanism provides the driving force transfer mechanism with a biasing force for biasing the bending portion bent by the turning operation of the bending operation knob in a direction of the approximately straight state.

3. An endoscope including a bending portion in an insertion portion, comprising:

first and second pulling members mounted on the bending portion;

a driving force transfer mechanism for transferring a rotary driving force generated by a bending operation knob to a corresponding pulling member and pulling one of the first and second pulling members mounted on the bending portion so as to change the bending portion between an approximately straight state and a bending state; and

a biasing mechanism including:

a coil spring which is a push spring provided approximately in parallel with a moving direction of the pulling members;

a fixing member for integrally fixing one end side of the coil spring on an operation portion;

a sliding member placed separately from and opposite an other end face of the coil spring;

an arm portion forming member for integrally connecting the sliding member to a predetermined position of a connecting member connected to the driving force transfer mechanism which is moved in conjunction with a turning operation of the bending operation knob, when the bending portion is bent by turning the bending operation knob and pulling the first pulling member, the biasing mechanism being adapted for providing a biasing force for biasing the bending portion bent by a bending operation of the bending operation knob in an approximately straight direction to the driving force transfer mechanism for transferring the rotary driving force of the bending operation knob operated on bending the bending portion in one direction corresponding to one of the first and second pulling members; and

a connection member axially connecting the driving force transfer mechanism to the one of the first pulling member and the second pulling member, wherein the connection member comprises mounting holes for receiving the arm portion forming member;

wherein the push spring imparts a compressive force to the sliding member for biasing the bending portion from the bending state to the approximately straight state.

4. The endoscope according to claim 1 , wherein the coil spring is placed in a space portion formed between the first and second pulling members which are mutually opposed, the first pulling member having a proximal end portion connected to one end of the driving force transfer mechanism and the second pulling member having a proximal end portion connected to another end of the driving force transfer mechanism.

5. The endoscope according to claim 3 , wherein the coil spring is placed in a space portion formed between the first and second pulling members which are mutually opposed, the first pulling member having a proximal end portion connected to one end of the driving force transfer mechanism and the second pulling member having a proximal end portion connected to another end of the driving force transfer mechanism.

6. An endoscope including a bending portion in an insertion portion, comprising:

first and second pulling members mounted on the bending portion;

bending operation knob for generating a driving force for pulling the pulling members in conjunction with a turning operation and bending the bending portion between an approximately straight state and a bending state;

a driving force transfer mechanism for transferring the driving force generated in conjunction with the turning operation of the bending operation knob to one of the first and second pulling members mounted on the bending portion: and

a biasing mechanism including:

a coil spring which is a pull spring provided approximately in parallel with a moving direction of the pulling members;

a fixing member for integrally fixing one end side of the coil spring on an operation portion;

a sliding member connected to an end face of the coil spring; and

an arm portion forming member for integrally connecting the sliding member to a predetermined position of a connecting member connected to the driving force transfer mechanism which is moved in conjunction with a turning operation of the bending operation knob, the biasing mechanism being adapted for providing a biasing force for turning the bending operation knob in a reverse direction to a direction of the turning operation by the sliding member being moved with movement of the driving force transfer mechanism and contacting an other end face of the coil spring, in a state where the bending portion is bent by turning the bending operation knob; and

a connection member axially connecting the driving force transfer mechanism to the one of the first pulling member and the second pulling member, wherein the connection member comprises mounting holes for receiving the arm portion forming member;

wherein the pull spring imparts a tensile force to the sliding member for biasing the bending portion from the bending state to the approximately straight state.

7. An endoscope including a bending portion in an insertion portion, comprising:

first and second pulling members mounted on the bending portion;

a driving force transfer mechanism for transferring a rotary driving force generated by bending operation knob to a corresponding pulling member and pulling one of the first and second pulling members mounted on the bending portion so as to change the bending portion between an approximately straight state and a bending state;

a biasing mechanism including:

a coil spring which is a pull spring provided approximately in parallel with a moving direction of the pulling members;

a fixing member for integrally fixing one end side of the coil spring on an operation portion;

a sliding member placed separately from and opposite an end face of the coil spring; and

an arm portion forming member for integrally connecting the sliding member to a predetermined position of a connecting member connected to the driving force transfer mechanism which is moved in conjunction with a turning operation of the bending operation knob, when the bending portion is bent by turning the bending operation knob and pulling the first pulling member, the biasing mechanism being adapted for providing a biasing force for biasing the bending portion bent by a bending operation of the bending operation knob in an approximately straight direction to the driving force transfer mechanism for transferring the rotary driving force of the bending operation knob operated on bending the bending portion in one direction corresponding to one of the first and second pulling members; and

a connection member axially connecting the driving force transfer mechanism to the one of the first pulling member and the second pulling member, wherein the connection member comprises mounting holes for receiving the arm portion forming member;

wherein the pull spring imparts a tensile force to the sliding member for biasing the bending portion from the bending state to the approximately straight state.

8. The endoscope according to claim 6 , wherein the coil spring is placed in a space portion formed between the first and second pulling members which are mutually opposed, the first pulling member having a proximal end portion connected to one end of the driving force transfer mechanism and the second pulling member having a proximal end portion connected to another end of the driving force transfer mechanism.

9. The endoscope according to claim 7 , wherein the coil spring is placed in a space portion formed between the first and second pulling members which are mutually opposed, the first pulling member having a proximal end portion connected to one end of the driving force transfer mechanism and the second pulling member having a proximal end portion connected to the another end of the driving force transfer mechanism.

10. The endoscope according to claim 8 , wherein the pulling member is inserted into a space in which the driving force transfer mechanism is arranged.

11. The endoscope according to claim 9 , wherein the pulling member is inserted into a space in which the driving force transfer mechanism is arranged.

12. The endoscope according to claim 1 , wherein the driving force transfer mechanism is a chain.

13. The endoscope according to claim 3 , wherein the driving force transfer mechanism is a chain.

14. The endoscope according to claim 6 , wherein the driving force transfer mechanism is a chain.

15. The endoscope according to claim 7 , wherein the driving force transfer mechanism is a chain.