Patent Publication Number: US-2022226007-A1

Title: Basket-type treatment tool for endoscope

Description:
TECHNICAL FIELD 
     The present invention relates to a basket-type treatment tool for an endoscope inserted into a body cavity and provided with a treatment unit which pinches and crushes a foreign substance such as a stone within the body cavity by a basket constituted by a plurality of elastic wires, and more particularly to a basket-type treatment tool for an endoscope in which the wires constructing the basket is hard to be damaged. 
     BACKGROUND ART 
     In general, a doctor uses a basket-type treatment tool for an endoscope having a basket unit which can project and set with respect to an elongated flexible sheath and is expandable and contractable like a basket, for recovering and crushing the foreign substance such as the stone within the body cavity. The basket-type treatment tool for the endoscope is adapted to be inserted into an endoscope channel in a state in which a basket unit is housed in a flexible sheath so as to be moved close to the foreign substance such as the stone within the body cavity, make the basket unit protrude away from a distal end of the flexible sheath, introduce the stone in the basket unit, contract the basket unit by pulling an operation wire connected to the basket unit, and pulverize or hold and draw the stone. 
     The basket unit corresponding to the treatment unit of the basket-type treatment tool for the endoscope is formed by bringing together distal ends and proximal ends of a plurality of basket wires so that the basket wires elastically contract and expand at intervals. Bringing together and retaining the distal ends of the basket wires is generally performed by bringing together with a tip and jointing by means of welding, silver brazing or adhesive agent or caulking. 
     As a literature describing a basket-type treatment tool for an endoscope, for example, the following patent literature 1 is listed up. 
     A technique described in the patent literature 1 is adapted to form a wire constructing a basket unit as a flattened wire and apply a strong directionality in a vertical direction to a flattened surface when the basket unit expands and contracts, thereby making the wire harder to be affected by an external force of a mucosal fluid attached to the basket wire when expanding and contracting and facilitating capture of the stone. 
     Further, as a literature describing a basket-type treatment tool for an endoscope in which distal ends of a plurality of basket wires are retained to a tip without welding, for example, the following patent literature 2 is listed up. 
     A technique described in the patent literature 2 can bind a plurality of elastic wires in a desired correct positional relationship at distal ends thereof by firmly fixing four metal short tubes as distal end tips and inserting two sets of U-shaped bent-back basket wires into the short tubes one by one near the bent-back portion, thereby inflating the basket unit to an expected shape. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Patent Unexamined Publication No. 2002-253557 
         Patent Literature 2: Japanese Patent Unexamined Publication No. 2000-41987 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in a basket-type treatment tool for an endoscope described in the patent literature 1, a wire constructing a basket is inserted into a distal end binding pipe (a distal end tip) in a distal end thereof and is joined by silver brazing. Therefore, deterioration of the wire is caused by heat transmission of the high-temperature (about 600° C. to 970° C.) to the wire when joining, and there is a problem that the wire may be damaged by a force applied to the distal end portion when crushing the stone. 
     The conventional basket-type treatment tool for the endoscope which is joined by laser welding or soldering has such a problem that the high-temperature heat is transmitted to the wire in the same manner as mentioned above, and has such a problem that the wire is damaged due to deterioration of an adhesive agent when the adhesive agent is used. Further, the conventional basket-type treatment tool for the endoscope in which the wires are brought together by a tip is not affected by the temperature applied to the wire, however, is hard to set a caulking force, and has such a problem that the wire is injured by an external pressure and is damaged. 
     Further, in a basket-type treatment tool for an endoscope described in the patent literature 2, it is necessary to insert four small-diameter soft basket wires into four short tubes respectively from a distal end direction thereof, thereby making it hard to manufacture the basket-type treatment tool for the endoscope. Further, an entire outer diameter of the tip is enlarged for disposing the short tubes in parallel, thereby generating a problem that the tip is out of a field of view of the endoscope. 
     Taking into consideration the above-described problems, an object of the present invention is to provide a basket-type treatment tool for an endoscope which is hard to be damaged in a wire constructing a basket and can be easily manufactured. 
     Solution to Problem 
     In order to achieve the object mentioned above, according to a first aspect of the present invention, there is provided a basket-type treatment tool for an endoscope comprising an elongated cylindrical flexible sheath, an operation wire which is inserted into a cylinder of the flexible sheath and is movable forward and backward in an axial direction within the cylinder by being operated to be pushed and pulled, a basket unit which is provided in a distal end of the operation wire and is formed in such a manner that a plurality of basket wires are elastically contracted or expanded, a distal end tip which has an inner diameter portion extending like a cylinder and brings together distal end sides of the plurality of basket wires to retain, a proximal end tip which brings together proximal end sides of the plurality of basket wires to retain, a distal end metal fitting which is attached to the distal end of the flexible sheathe and inserts the operation wire with the basket unit thereto, and an operation unit for operating the operation wire to move forward and backward, wherein the distal end tip puts a turned-back portion formed by turning back an approximately center portion of the basket wire on an approximately columnar first rib fixed in a perpendicular direction to a tube axis of the distal end tip to retain, in which a direction toward the distal end tip is called as a distal end side, and a direction toward the operation unit is called as a proximal end side. 
     Further, according to a second aspect of the present invention, a groove is formed in the perpendicular direction to the tube axis in a distal end of the distal end tip, and the first rib is fixed to the groove, in the basket-type treatment tool for the endoscope according to the first aspect. 
     Further, according to a third aspect of the present invention, the inner diameter portion of the distal end tip has a small inner diameter area having a predetermined inner diameter for bringing together the basket wires to retain, and a large inner diameter area positioned closer to the proximal end side than the small inner diameter area, having a greater inner diameter than the small inner diameter area and allowing the basket wires to be movable in an inner portion thereof, in an axial direction, in the basket-type treatment tool for the endoscope according to the first aspect. According to a fourth aspect of the present invention, the inner diameter portion of the distal end tip has a small inner diameter area having a predetermined inner diameter for bringing together the basket wires to retain, and a large inner diameter area positioned closer to the proximal end side than the small inner diameter area, having a greater inner diameter than the small inner diameter area and allowing the basket wires to be movable in an inner portion thereof, in an axial direction, in the basket-type treatment tool for the endoscope according to the second aspect. 
     Further, according to a fifth aspect of the present invention, the basket unit is constructed by two basket wires, an approximately columnar second rib is fixed to a proximal end side of the distal end tip, the turned-back portion of one basket wire in the basket wires is put on the first rib, and the turned-back portion of the other basket wire is put on the second rib, in the basket-type treatment tool for the endoscope according to the first aspect. According to a sixth aspect of the present invention, the basket unit is constructed by two basket wires, an approximately columnar second rib is fixed to a proximal end side of the distal end tip, the turned-back portion of one basket wire in the basket wires is put on the first rib, and the turned-back portion of the other basket wire is put on the second rib, in the basket-type treatment tool for the endoscope according to the second aspect. According to a seventh aspect of the present invention, the basket unit is constructed by two basket wires, an approximately columnar second rib is fixed to a proximal end side of the distal end tip, the turned-back portion of one basket wire in the basket wires is put on the first rib, and the turned-back portion of the other basket wire is put on the second rib, in the basket-type treatment tool for the endoscope according to the third aspect. According to an eighth aspect of the present invention, the basket unit is constructed by two basket wires, an approximately columnar second rib is fixed to a proximal end side of the distal end tip, the turned-back portion of one basket wire in the basket wires is put on the first rib, and the turned-back portion of the other basket wire is put on the second rib, in the basket-type treatment tool for the endoscope according to the fourth aspect. 
     Further, according to a ninth aspect of the present invention, the second rib is fixed to the large inner diameter area in the basket-type treatment tool for the endoscope according to the seventh aspect. According to a tenth aspect of the present invention, the second rib is fixed to the large inner diameter area in the basket-type treatment tool for the endoscope according to the eighth aspect. 
     Effect of Invention 
     The treatment tool for the endoscope according to the present invention can retain the distal end of the basket wire to the distal end tip without caulking by putting the turned-back portion formed by turning back the approximately center portion of the basket wire on the approximately columnar first rib fixed in the perpendicular direction to the tube axis of the distal end top to retain. Therefore, the basket wire is hard to be damaged and the treatment tool for the endoscope can be easily manufactured. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view showing an overall configuration of a basket-type treatment tool for an endoscope according to an embodiment of the present invention. 
         FIGS. 2A to 2E  are views showing a distal end tip of a basket-type treatment tool for an endoscope according to an embodiment 1 of the present invention. 
         FIGS. 3A and 3B  are views for describing a difference of the distal end tip of the basket-type treatment tool for the endoscope according to the embodiment 1 of the present invention from a conventional distal end tip. 
         FIGS. 4A and 4B  are views for describing a dimension of the distal end tip according to the embodiment 1 of the present invention. 
         FIGS. 5A to 5D  are views for describing attachment of a basket wire to the distal end tip according to the embodiment 1 of the present invention. 
         FIGS. 6A to 6D  are views showing a distal end tip of a basket-type treatment tool for an endoscope according to an embodiment 2 of the present invention. 
         FIGS. 7A to 7C  are views showing a distal end tip of a basket-type treatment tool for an endoscope according to an embodiment 3 of the present invention. 
         FIGS. 8A to 8D  are views for describing an operation example of a basket-type treatment tool for an endoscope to which the present invention is applied. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A description will be in detail given below of an embodiment of a basket-type treatment tool for an endoscope according to the present invention with reference to the accompanying drawings. First of all, a description will be given of an overall structure of the basket-type treatment tool for the endoscope according to the embodiment of the present invention. 
     Embodiment 1 
     [Overall Structure] 
     As shown in  FIG. 1 , a basket-type treatment tool for an endoscope according to the present embodiment is provided with an elongated flexible sheath  2  which has an operation unit  10  attached to a proximal end thereof and is made of a resin or a coil, an operation wire  3  which is inserted into the flexible sheath  2  so as to be movable forward and backward, a cylindrical distal end metal fitting  20  which is arranged in a distal end of the flexible sheath  2  and is made of a hard metal material, and a foreign substance crushing basket unit  40  which is coupled to a distal end of the operation wire  3  and serves as a treatment unit capable of projecting and setting with respect to the flexible sheath  2  by pushing the operation wire  3  to the distal end side or pulling the operation wire  3  to the proximal end side on the basis of an operation of the operation unit  10 . 
     In the present embodiment, a direction toward the operation unit  10  which is right in  FIG. 1  is called as the proximal end side, and a direction toward the distal end tip  6  which is left in  FIG. 1  is called as the distal end side. 
     The operation unit  10  is provided with a grip part  14  which is attached to the proximal end of the operation wire  3  via an operation pipe  12 , and an operation unit body  11  through which the operation pipe  12  of the grip part  14  attached to the operation wire  3  passes, to which a water supply port  13  is opened, and which projects and sets the basket unit  40  in the distal end of the operation wire  3  with respect to the flexible sheath  2  by moving forward and backward the grip part  14 . The water supply port  13  is communicated with a space in the cylinder of the operation unit body  11  in an inner end portion thereof, and is configured to attach an injection (not shown) thereto and allow a drug solution to be fed into the flexible sheath  2 . 
     The basket unit  40  is constructed by a plurality of basket wires  41  and  42  obtained by turning back an elongated linear twisted wire approximately at the center and forming a distal end in the turned-back portion (in the present embodiment, the basket unit  40  is constituted by four turned-back portions obtained by turning back two basket wires), the distal end tip  6  which brings together the turned-back distal ends of the basket wires  41  and  42  to retain and is a feature of the present embodiment, and a proximal end tip  7  which brings together the proximal ends of the basket wires  41  and  42  to fix. The treatment unit is formed in such a manner that a plurality of basket wires  41  and  42  elastically contract and expand at intervals. 
     The basket unit  40  is self-biased in such a manner that each of the basket wires  41  and  42  is curved and inflated outward, the basket wires  41  and  42  are arranged in a stereoscopically linear symmetrical relationship around a center axis of the basket unit  40 , and the basket unit  40  is configured to be contracted within the flexible sheath  2  and be inflated and expanded by a self-biasing force in a protruding state from the distal end of the flexible sheath  2  so as to form an approximately basket shape. 
     [Description of Overall Motion] 
     The basket-type treatment tool for the endoscope according to the present embodiment constructed as described above is inserted into a body cavity of a patient through a channel of an endoscope device previously inserted into the body cavity of the patient and is used for crushing a stone to be recovered. An example of this operation will be described with reference to  FIGS. 8A to 8D . 
     The operation with the basket-type treatment tool for the endoscope is performed by a step of pulling the operation wire and inserting the flexible sheath  2  in a state in which the basket unit in the distal end is drawn into an inner portion and is contracted into a biliary duct  220  within a duodenal papilla  210 , by a doctor, as shown in  FIG. 8A , a next step of pushing out the operation wire, opening the basket unit  40  from the distal end of the flexible sheath  2  and moving to a far position from a stone  230 , as shown in  FIG. 8B , a next step of protruding the operation wire, drawing the operation wire into the flexible sheath  2  and trapping the stone  230  into a gap of the basket unit  40 , as shown in  FIG. 8C , and a further step of further drawing the basket unit  40  into the flexible sheath  2 , pinching between the distal end metal fitting in the distal end of the flexible sheath  2  and the basket unit  40  and constricting the stone  230 , thereby crushing the stone  230 , as shown in  FIG. 8D . 
     [Structure of Distal End Tip] 
     The distal end tip  6  corresponding to the feature of the present embodiment has been conventionally constructed, for example, by inserting the distal ends of four basket wires and fixing them by caulking or welding. In order to reduce the wire damage and easily manufacture, the distal end tip  6  of the present embodiment is constructed by inserting two basket wires  41  and  42  into an opening portion in a distal end of the distal end tip  6  in a state of being turned back as shown in  FIG. 5A , putting a rib  6   b  on turned-back portions  41   a  and  42   a  of the basket wires  41  and  42  as shown in  FIG. 5B , cutting both ends of the rib  6   b  and pressing the basket wires  41  and  42  into the distal end tip as shown in  FIGS. 5C and 5D , details of which will be mentioned later. Next, a detailed structure thereof will be described. 
     A description will be given of the distal end tip  6  corresponding to the feature of the present embodiment with reference to  FIGS. 2A to 4B . 
       FIG. 2A  shows an outer appearance diagram of the distal end tip  6 ,  FIG. 2B  shows a view of  FIG. 2A  as seen from the distal end side (an upward direction of  FIG. 2A ),  FIG. 2C  shows a cross sectional view along a line A-A in  FIG. 2B ,  FIG. 2D  shows a cross sectional view along a line B-B in  FIG. 2A , and  FIG. 2E  shows a cross sectional view along a line C-C in  FIG. 2A , in which the basket wires  41  and  42  are shown in a state in which they are not expanded like a basket, but are closed. 
     As shown in  FIGS. 2A and 2C , the distal end tip  6  is constructed by a distal end portion  6   e  which is formed into an approximately semispherical shape in a distal end side thereof so as to prevent an inner wall of the body cavity from being injured, a hollow tip main body  6   a  which is formed in a proximal end side thereof into a tubular shape which can be fitted to a tip outer tube  6   c  mentioned later, and includes a distal end tube portion  6   f  having a small inner diameter area N, and a tubular tip outer tube  6   c  which is fitted to an outer periphery of the distal end tube portion  6   f  of the tip main body  6   a  and is fixed by laser welding, and has a tubular inner diameter portion with level difference as a whole. 
     As shown in  FIG. 2C , the inner diameter portion has the small inner diameter area N having a predetermined inner diameter for bringing together the basket wires  41  and  42  mentioned later to retain, and a large inner diameter area M which is positioned closer to the proximal end side than the small inner diameter area, has a larger diameter than the small inner diameter area N, and allows the basket wires  41  and  42  to be movable in an inner portion thereof. 
     The distal end tip  6  is provided in the distal end of the distal end portion  6   e  of the tip main body  6   a  with grooves  6   d  and  6   d  at symmetrical positions at the center of the perpendicular direction to the tube axis, and an axial length (groove depth) of the grooves  6   d  and  6   d  is desirably set to the same level as a length obtained by adding a diameter of the basket wire and a diameter of a rib  6   b  mentioned later, as shown in  FIGS. 2A to 2C . 
     Further, an approximately columnar first rib  6   b  is fitted and fixed to the grooves  6   d  and  6   d . The respective wire turned-back portions  41   a  and  42   a  of the basket wires  41  and  42  are put on the first rib  6   b . A length of the rib  6   b  is preferably set to about the same length as the diameter of the distal end portion  6   e  of the distal end tip  6  since the protruding portion of the distal end tip  6  may injure the inner wall of the body cavity when being fixed to the groove  6   d  if the outward protruding portion of the distal end tip  6  is long. 
     Further, a part closer to the proximal end side than the wire turned-back portion  41   a  and the wire turned-back portion  42   a  is pressed into the distal end tube portion  6   f , so that outer peripheries of the basket wires  41  and  42  are partly retained respectively in a state of being in contact with the distal end tube portion  6   f , as shown in  FIG. 2D . 
     In the meantime, the tip outer tube  6   c  forms an inner diameter fitting to an outer periphery of the distal end tube portion  6   f . As shown in  FIGS. 2C to 2E , a large inner diameter area having a gap  6   g  corresponding to a thickness of the distal end tube portion  6   f  is positioned between the basket wires  41  and  42  and an inner periphery of the tip outer tube  6   c.    
     In the present embodiment, the basket wires  41  and  42  are structured such that the elongated linear twisted wire is turned back approximately at the center portion and the turned-back portion forms the distal end of the basket wire, thereby forming a pair by two basket wires  41  and  41  and a pair by two basket wires  42  and  42  in  FIG. 1 . However, the structure is not limited to this, but the basket may be constructed by three pairs, each pair being constituted by two basket wires. 
     [Dimension] 
     Next, a dimension of the distal end tip  6  will be described with reference to  FIGS. 4A and 4B  (in which the basket wires  41  and  42  and the rib  6   b  are not shown). A specific example of dimensions of the respective members is an example in a case where a diameter of the basket wires  41  and  42  is set to 0.35 mm and two pairs of basket wires, that is, four basket wires are employed, however, the dimension is not limited to this. 
     An inner diameter L 4  of the small inner diameter area N in the distal end tube portion  6   f  of the distal end tip  6  is a diameter which can press a part closer to the proximal end side than each of the wire turned-back portions  41   a  and  42   a  of the basket wires  41  and  42  thereinto and can retain a part of the outer peripheries of the basket wires  41  and  42  in an internal contact manner, as mentioned above, for example, about 0.86 mm. Further, a length L 2  of the small inner diameter area N is about 1.5 mm, for example. 
     An inner diameter L 1  of the distal end side of the distal end portion  6   e  is larger than the inner diameter L 4  of the distal end tube portion  6   f  for housing each of the turned-back portions  41   a  and  42   a  of the basket wires  41  and  42  and the rib  6   b , for example, about 1.2 mm. 
     An inner diameter L 5  of the tip outer tube  6   c  is approximately the same diameter as an outer diameter of the distal end tube portion  6   f  for fitting to the distal end tube portion  6   f , for example, about 1.2 mm. 
     A length L 3  of the large inner diameter area M of the tip outer tube  6   c  is required to be such a length that the basket wires  41  and  42  mentioned above are movable, and is necessarily at least about 1.5 times to 6 times of the inner diameter L 5 , for example, about 2 mm, and a length L 6  of the tip outer tube  6   c  is about 3 mm, for example. 
     [Assembling Method] 
     Next, a description will be given of a method of attaching the basket wires  41  and  42  to the distal end tip  6  with reference to  FIGS. 5A to 5D . 
     The assembling method first performs a step of inserting the proximal end sides of the basket wires  41  and  42  turned back approximately at the center portion of the elongated linear twisted wire from the distal end side of the distal end tip  6  toward the proximal end side (in a direction of an arrow Y in the drawing) as shown in  FIG. 5A , next a step of passing the rib  6   b  through the gap of the turned-back portions  41   a  and  42   a  in a state in which each of the wire turned-back portions  41   a  and  42   a  of the basket wires  41  and  42  protrude out of the distal end tip  6  as shown in  FIG. 5B , and a step of pressing the basket wires  41  and  42  toward the proximal end side of the distal end tip  6  (in a direction of an arrow Z in the drawing). 
     Next, the present assembling method performs a step of fitting the rib  6   b  to the groove  6   d  and fixing the rib  6   b  to the groove  6   d  by laser welding as shown in  FIG. 5C , and a step of cutting the protruding portion of the rib  6   b  protruding out of the distal end tip  6  as shown in  FIG. 5D . 
     According to the assembling method, in the distal end tip according to the present embodiment, the wire is not damaged by thermal welding, and the distal end tip can be easily manufactured since the wire is pressed into the distal end tip in a state in which two turned-back portions are put on the rib as the distal end. 
     In the present embodiment, there is shown the example in which the protruding portion is cut after the rib  6   b  is fixed to the groove  6   d . However, the structure is not limited to this, but the length of the rib  6   b  may be cut to the length which does not protrude out of the distal end tip and the rib  6   b  may be fixed to the groove  6   d.    
     Effect 
     As mentioned above, the basket-type treatment tool for the endoscope  1  shown in the present embodiment is configured to press the wire into the distal end tip in a state in which the turned-back portions  41   a  and  42   a  obtained by turning back two basket wires  41  and  42  are set as the distal end and put on the approximately columnar rib  6   b  as described above. The basket-type treatment tool for the endoscope  1  has the following effects. 
     The basket-type treatment tool for the endoscope  1  shown in the present embodiment can bring together the basket wires  41  and  42  with the distal end tip by putting each of the wire turned-back portions  41   a  and  42   a  of the basket wires  41  and  42  on the approximately columnar rib  6   b  and fixing the rib  6   b  to the groove  6   d  of the distal end tip  6  as described above without applying any heat of welding to each of the turned-back portions  41   a  and  42   a  of the basket wires  41  and  42 , and is no danger of damage in the basket wire due to the heat. Further, in addition to this, in the present basket-type treatment for the endoscope  1 , the basket wires  41  and  42  can be retained within the small inner diameter area N, since the basket wires  41  and  42  are pressed into the small inner diameter area N of the distal end tip. 
     Further, in the basket-type treatment tool for the endoscope  1  according to the present embodiment, the columnar outer periphery of the rib  6   b  smoothly comes into contact with the inner side of the wire turned-back portions  41   a  and  42   a  when the basket wires  41  and  42  are put, since the rib  6   b  is formed into the approximately columnar shape which has no angles. Therefore, the force applied to the wire turned-back portions  41   a  and  42   a  is dispersed in a case where the strong force is applied when crushing the stone, in comparison with the case of the angled shape, so that basket wires  41  and  42  are hard to be damaged. 
     Further, the present basket-type treatment tool for the endoscope  1  is a simple structure in which the rib  6   b  is fixed to the distal end tip  6  and the basket wire is put thereon. Thus, the present basket-type treatment tool for the endoscope  1  can be easily manufactured, and is in no danger of becoming too large in the outer diameter of the distal end tip to be out of the visual field of the endoscope. 
     Further, in the present basket-type treatment tool for the endoscope  1 , the basket wires  41  and  42  move in an allowable range formed by the gap  6   g  when gripping the stone since the gap  6   g  is provided between the basket wires  41  and  42  and the tip outer tube  6   c . Therefore, the basket-type treatment tool for the endoscope is hard to be incarcerated and the incarceration is easy to be cancelled even in a case where being incarcerated. 
     More specifically, the basket-type treatment tool for the endoscope  1  according to the present embodiment is provided with the gap  6   g  with respect to the inner periphery of the tip outer tube  6   c  of the distal end tip  6  in a state in which the basket wires  41  and  42  are narrowed. Thus, as shown in FIG.  3 A, even in a case where the basket wires  41  and  42  ( 42  is not shown) are expanded like a basket and the stone is stuck in the inner portion of the basket unit  40  and does not move, the basket wires  41  and  42  can move in the inner portion of the tip outer tube  6   c  in a direction of X (a direction in which the basket wires  41  and  42  is expanded like a basket and narrowed) by operating the operation wire  2  to push and pull. Therefore, the stone can be moved little by little and a gap is formed between the basket wires  41  and  42  and the stone gradually, thereby cancelling the incarceration. 
     Further, the basket wire  41  is folded at a small (acute) folding angle θ 2  from the protruding position from the distal end tube portion  6   f  having no gap in a case where the tip outer tube  6   c  is not provided, as shown in  FIG. 3B . On the contrary, in the basket-type treatment tool for the endoscope  1  according to the present embodiment, a folding angle θ 1  from the protruding position from the tip outer tube  6   c  is greater (obtuse) as shown in  FIG. 3A , thereby achieving an effect that the basket wire is less eaten into the stone and is hard to be incarcerated. 
     Embodiment 2 
     Next, a description will be given of an second embodiment 2 of the basket-type treatment tool for the endoscope  1  according to the present invention with reference to  FIGS. 6A to 6D . 
       FIG. 6A  shows an outer appearance diagram of a distal end tip  6 ,  FIG. 6B  shows a view of  FIG. 6A  as seen from a distal end side (an upward direction of  FIG. 6A ),  FIG. 6C  is a cross sectional view along a line D-D in  FIG. 6B , and  FIG. 6D  shows a cross sectional view along a line E-E in  FIG. 6B , in which basket wires  41  and  42  are shown in a state in which the basket wires  41  and  42  are not expanded like a basket, but are closed. 
     The other structures than the distal end tip are same as those of the embodiment 1 and a description thereof will be omitted. 
     In the embodiment mentioned above, there is shown the example in which the rib  6   b  putting each of the turned-back portions  41   a  and  42   a  of the basket wires  41  and  42  thereon is fixed to the groove  6   d  of the distal end tip  6 . However, the structure is not limited to this, but the basket-type treatment tool for the endoscope  1  according to the embodiment 2 may be structured, for example, as shown in  FIGS. 6A to 6D , such that two ribs are fixed to the distal end tip  6  and the basket wire is put on each of the ribs. 
     More specifically, in the basket-type treatment tool for the endoscope according to the embodiment 2, as shown in  FIGS. 6A to 6D , a groove  6   d  is formed in a distal end portion  6   e  of the distal end tip in the same manner as the embodiment 1, a first rib  6   b  putting the turned-back portion  41   a  of the basket wire  41  thereon is fixed to the groove  6   d , and an approximately columnar second rib  6   h  putting the turned-back portion  42   a  of the basket wire  42  thereon is fixed to a large inner diameter area M of a tip outer tube  6   c . The rib  6   h  may be directly welded to an inner portion of the tip outer tube  6   c  by laser, or a groove may be formed in a proximal end of the tip outer tube  6   c  at the center in a perpendicular direction to the tube axis and the rib  6   h  may be fixed to the groove. 
     The basket wire  41  is arranged in the large inner diameter area M so as to avoid the rib  6   h.    
     In the basket-type treatment tool for the endoscope according to the present embodiment, the approximately columnar rib  6   b  putting the wire turned-back portion  41   a  of the basket wire  41  thereon is fixed to the groove  6   d  of the distal end tip  6 , and the approximately columnar rib  6   h  putting the turned-back portion  42   a  of the basket wire  42  thereon is fixed within the tip outer tube  6   c , as described above. Thus, the basket wires  41  and  42  can be brought together by the distal end tip without applying any heat generated by welding to each of the turned-back portions  41   a  and  42   a  of the basket wires  41  and  42 , and it is possible to prevent the basket wire from being damaged by the heat. 
     Further, in the present basket-type treatment tool for the endoscope, the columnar outer peripheries of the ribs  6   b  and  6   h  smoothly comes into contact with the inner side of the wire turned-back portions  41   a  and  42   a  when the basket wires  41  and  42  are put, since the ribs  6   b  and  6   h  are formed into the approximately columnar shape which has no angles. Therefore, the force applied to the wire turned-back portions  41   a  and  42   a  is dispersed in a case where the strong force is applied when crushing the stone, in comparison with the case of the angled shape, so that basket wires  41  and  42  are hard to be damaged. 
     Embodiment 3 
     Next, a description will be given of an embodiment 3 of the basket-type treatment tool for the endoscope  1  according to the present invention with reference to  FIGS. 7A to 7C . 
       FIG. 7A  shows an outer appearance diagram of a distal end tip  50 ,  FIG. 7B  shows a view of  FIG. 7A  as seen from a distal end side (in an upward direction of  FIG. 7A ), and  FIG. 7C  shows a cross sectional view along a line F-F in  FIG. 7B , in which basket wires  41  and  42  are shown in a state in which they are not expanded like a basket, but are closed. 
     The other structures than the distal end tip are the same as those of the embodiment 1, and a description thereof will be accordingly omitted. 
     In the embodiment mentioned above, there is shown the example in which the distal end tip is constructed by assembling two members constituted by the tip main body and the tip outer tube. However, the structure is not limited to this, but the basket-type treatment tool for the endoscope according to the embodiment 3 may be structured such that the distal end tip  50  is formed into a tubular shape, grooves  50   b  and  50   b  are provided in a distal end thereof at the center in a perpendicular direction to a tube axis, and an approximately columnar rib  50   a  on which each of the wire turned-back portions  41   a  and  42   a  of the basket wires  41  and  42  is put, is fitted and fixed to the groove  50   a  and  50   b.    
     In the basket-type treatment tool for the endoscope according to the present embodiment, the basket wires  41  and  42  can be brought together by the distal end tip without applying any heat by welding to each of the turned-back portions  41   a  and  42   a  of the basket wires  41  and  42  by fixing the approximately columnar rib  50   a  on which each of the wire turned-back portions  41   a  and  42   a  of the basket wires  41  and  42  is put to the groove  50   b  of the distal end tip  50 , in the same manner as the embodiment mentioned above. Therefore, it is possible to prevent the basket wire from being damaged by the heat. 
     Further, in the present basket-type treatment tool for the endoscope, the outer periphery of the column of the rib  50   a  smoothly comes into contact with the inner side of the wire turned-back portions  41   a  and  42   a  when the basket wires  41  and  42  are put thereon since the rib  50   a  is formed into the approximately columnar shape which has no angles. Therefore, the force applied to the wire turned-back portions  41   a  and  42   a  is dispersed in a case where the strong force is applied when crushing the stone, in comparison with the case of the angled shape, so that basket wires  41  and  42  are hard to be damaged. 
     The rib on which each of the turned-back portions  41   a  and  42   a  of the basket wires  41  and  42  is put may be fixed at two positions constituted by the distal end side and the proximal end side by combining the present embodiment with the embodiment 2 mentioned above.