hereafter , the present invention is described more particularly by way of its preferred embodiments with reference to the accompanying drawings . in the following description of preferred embodiments , those component parts which are equivalent or identical with the counterparts in the above - discussed prior art are designated by similar reference numerals or characters to avoid repetitions of same explanations . referring to fig1 and 2 , there is shown a first embodiment of the present invention . in these figures , indicated at 25 is an anchor pipe which is fixed to a connecting ring 18 on the side of an angle section 2 a of an endoscopic insertion instrument 2 by means of an anchor pin 23 . similarly to the counterpart in the above - described prior art , the anchor pipe 25 is constituted by a large diameter portion 25 a and a small diameter portion 25 b , and a fore end portion of a tightly closed sheathing coil 22 of an operating wire 21 is fixedly fitted in the large diameter portion 25 a . more specifically , as shown in fig2 the fore end of the tightly closed sheathing coil 22 which is fitted in the large diameter portion 25 a in the shape of a circular tube is abutted against a stepped portion between the large and small diameter portions 25 a and 25 b and securely fixed to the anchor pipe 25 by conducting laser spot welding from the side of circumferential surface of the large diameter portion 25 a . the tightly closed sheathing coil 22 may be welded to the anchor pipe 25 only at one spot because , once assembled into an endoscopic insertion instrument , they will not be subject to large external forces . however , the number of welding spots may be increased for the purpose of stabilizing the connection of these parts . a seal material 30 is applied to form a shield portion on and around the circumference of the closed sheathing guide coil 22 on the posterior side of the anchor pipe 25 , over a predetermined axial length l across a proximal end of the anchor pipe 25 . in this instance , the seal material 30 is of a soft and resilient type which can fill in and hermetically seal the gaps between the helices of the closed sheathing coil 22 which is in the range of the above - mentioned axial length l . the closed sheathing coil 22 , however , is flexible in bending directions . namely , the closed sheathing coil 22 is formed into the shape of a tunnel which is circumferentially closed by the seal material 30 and which is extended across the proximal end of the anchor pipe 25 over the axial length l . thus , the closed sheathing guide coil 22 is partially hermetically closed by the seal material 30 as described above , for the purpose of preventing a flux from getting into the coil 22 at the time of joining and soldering the connecting rings 17 and 18 to each other . at this time , a flux is used for the purpose of letting solder sufficiently get on and spread over broad joining surface areas of the connecting rings 17 and 18 which are fitted one on the other substantially in a tightly closed state . accordingly , the coil portion which is hermetically encased in the seal material 30 functions to block intrusion of the flux . in order to produce the flux blocking function to a sufficient degree , the seal material 30 should be applied over the axial length l which extends at least as far as a position on the proximal side of the inner connecting ring 17 on the part of the angle section 2 b , more specifically , a position inward of the coil tube 10 as shown in fig1 . with the arrangements just described , at the time of joining the angle section 2 b with the flexible body 2 a of the insertion instrument 2 by soldering , a sufficient amount of flux can be filled into the apertures 19 in the connecting ring 17 on the side of the angle section 2 b . as solder is put into the apertures 19 , the flux is pushed apart and an excess amount of flux is caused to exude from a gap space between the two connecting rings 17 and 18 in a direction radially inward of the flexible body 2 a . however , at this position , the closed sheathing coil 22 is hermetically enshrouded in the seal material 30 , so that there is no possibility of the flux depositing on the operating wire 21 which is threaded in the closed sheathing coil 22 . accordingly , the joint construction according to the invention contributes to protect operating wire 21 against oxidative deteriorations by the flux and to prolong the service life of the operating wire 21 by suppressing the abrasive wear which results from sliding contact with the closed sheathing coil 22 . in addition , the joint construction contributes to ensure smooth sliding movements of the operating wire 21 within the closed sheathing coil 22 . further , the use of a sufficient amount of flux in joining and fixing the flexible body portion 2 a and angle section 2 b with each other makes it possible to distribute solder over broad joining surface areas of the connecting rings 17 and 18 and thus to improve the strength of connection between the two connecting rings . from the standpoint of preventing intrusion of a flux , it is desirable to increase as much as possible the axial length of coil portion which is circumferentially sealed with the seal material 30 . however , resistance to bending movements is increased to a certain degree in case the seal material 30 is applied in such a way to fill in interstices between individual helices of the closed sheathing coil 22 even if the seal material 30 is of a soft and resilient type . in this connection , considering that applied flux tends to exude and flow into the insertion instrument from end portions of the connecting ring 18 on the side of the angle section 2 b , the range of application of the seal material 30 should be extended at least to a position further on the proximal side of the proximal end of the connecting ring 18 . at the joint of the flexible body 2 a and the angle section 2 b of the insertion instrument , the connecting ring 18 on the side of the angle section 2 b and the connecting 17 on the side of the flexible body 2 a are located in an unbendable rigid portion in the path of the operating wire 21 . the fore end of the closed sheathing coil 22 is connected to the anchor pipe 25 which is located in the unbendable rigid portion . in this regard , it is important to locate the anchor pipe 25 within the range of the unbendable rigid portion . the flexible body 2 a is less bendable in a transitional portion which extends over a certain length from the unbendable rigid portion . accordingly , a drop in bending flexibility by application of the seal material 30 around the circumference of the closed sheathing coil 22 will not give rise to a problem in particular as long as it is located in the above - mentioned transitional portion of the flexible body 2 a . accordingly , a shield portion which is formed on and around the closed sheathing coil 22 by application of the seal material 30 can be extended as far as the less bendable transitional portion . more specifically , the seal material 30 is applied such that the shield portion is preferably extended as far as a position slightly inward of the coil tube 10 in the flexible body 2 a . by so arranging the shield portion , it becomes possible to prevent intrusion of a flux more securely without impairing necessary bending flexibility of the closed sheathing coil 22 . turning now to fig3 there is shown a second embodiment of the present invention , in which a shield is formed by fitting a flexible shield tube 40 on the circumference of the closed sheathing coil 22 instead of applying a seal material thereon . similarly to the shield portion in the foregoing first embodiment , the flexible tube 40 has a length which extends from a position in the anchor pipe 25 to a position in the less bendable transitional portion of the flexible body 2 a . in this instance , for example , the flexible tube 40 is formed of a thermally contractible material and tightly fitted on the closed sheathing coil 22 by application of heat after it is set in position on the anchor pipe 25 and the sheathing coil 22 . upon fitting the flexible shielding tube 40 on the closed sheathing coil 22 in this manner , the interstices between the individual helices of the coil 22 are completely closed by the tube 40 to block a flux which might otherwise intrude into the closed sheathing coil 22 and deposit on the operating wire 21 when soldering the connecting rings 17 and 18 for joining the angle section 2 b to the flexible body 2 a of the insertion instrument 2 . in the case of the embodiment shown in fig3 the flexible shield tube 40 is fitted on the closed sheathing tube 22 before inserting and fixing same to the anchor pipe 25 . however , as shown in fig4 a flexible shield tube 41 may be fitted on the closed sheathing coil 22 and the large diameter portion 25 a after inserting the closed sheathing coil 22 into the anchor pipe and securely fixing these parts together by laser spot welding or by other suitable fixation means . in this case , it is important for the flexible shield tube 41 , which is fitted on the closed sheathing coil 22 , to be arranged to cover at least proximal end portions of the large diameter portion 25 a of the anchor pipe 25 .
in an endoscopic insertion instrument having a rigid tip end section , an elongated flexible body , and an angle section connected between the rigid tip end section and the flexible body , a joint construction connects an angle section to the fore end of the flexible body . a couple of connecting rings are provided opposingly at joining ends of the angle section and the flexible body . at least one aperture is provided in an outer one of the connecting rings to feed a flux . at least one angle section operating is passed through the connecting ring . the operating wire is encased in a sheathing coil , the fore end of which is fixed to the inner one connecting rings . to prevent flux from getting into the closed sheathing coil , a shield portion is formed around an outer periphery of the sheating coil over a predetremined range in axial length .