Abstract:
A catheter has an outer tube capable of turning an inner tube smoothly. The catheter comprises an inner tube  11  having a leading end portion formed into a suitable shape matching an affected part  18 , an outer tube  12  fitted movably on the inner tube  11  and a joint mechanism for enabling the inner tube  11  to move integrally with the outer tube  12  without preventing the movement of the outer tube  12.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a catheter and, more particularly, to a catheter capable of changing the direction of the leading end portion of an inner tube, guided in an outer tube, in a human body.  
           [0003]    2. Description of Related Art  
           [0004]    The catheter of the aforementioned type is disclosed in Unexamined Published Japanese Patent Application No. 2-13472 or 4-231068, for example. In this catheter of the prior art, the leading end portion of the inner tube can be changed in direction by turning the inner tube relative to the outer tube which is held stationary. Moreover, a clearance is left between the inner tube and the outer tube so as to allow turning of the former relative to the latter.  
           [0005]    However, the aforementioned catheter must have an external diameter as small as possible in its entirety and the internal diameter of the inner tube must have an internal diameter as large as possible due to the necessity of maintaining a desired flow rate of a contrast medium through the inner tube. The clearance is made as small as possible in the manufacture because of these conflicting demands. When the catheter is brought into actual use even if the inner tube and the outer tube are made of materials having low coefficients of friction, a drawback arises since the inner tube interferes with the stationary outer tube so that the turning motion of the inner tube relative to the outer tube cannot be effected smoothly. Since the relative position of the outer tube to the inner tube is not fixed, they may go out of the desired position relative to each other while the catheter is being used. Since the relative position of the outer tube to the inner tube is not indicated, the catheter is not convenient to use.  
         SUMMARY OF THE INVENTION  
         [0006]    Therefore, the object of the present invention is to provide a catheter having none of the foregoing defects.  
           [0007]    In order to achieve this object, according to a first aspect of the invention, there is provided a catheter comprising: an inner tube having a leading end portion formed into a suitable shape matching an affected part; an outer tube fitted movably on said inner tube; and a joint mechanism for enabling said inner tube to move integrally with said outer tube without preventing the movement of said outer tube. Thus, the change in the direction of the inner tube is made by the integral turning motion with the outer tube so that it can be made smoother than the case when the inner tube turns relative to the outer tube.  
           [0008]    According to a second aspect of the invention, there is provided a catheter comprising: an inner tube having a leading end portion formed into a suitable shape matching an affected part; an outer tube fitted movably on said inner tube; and a lock mechanism for stopping/fixing the movement of said outer tube at an arbitrary position. Thus, the movement of the outer tube on the inner tube can be stopped/fixed at an arbitrary position by the lock mechanism so that the catheter can be prevented from going out of position while it is used.  
           [0009]    According to a third aspect of the invention, there is provided a catheter comprising: an inner tube having a leading end portion formed into a suitable shape matching an affected part; an outer tube fitted movably on said inner tube; and an indication mechanism for indicating the stroke of the movement of said outer tube. Thus, the stroke movement of the outer tube on the inner tube can be indicated by the indication mechanism so that the catheter can be easily handled. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a side elevation showing a catheter according to a first embodiment of the invention;  
         [0011]    [0011]FIG. 2 is a section taken along line A-A of FIG. 1;  
         [0012]    [0012]FIG. 3 is a view showing the state in which the catheter shown in FIG. 1 is used;  
         [0013]    [0013]FIG. 4 is a side elevation showing a catheter according to a second embodiment of the invention;  
         [0014]    [0014]FIG. 5 is a section taken along line B-B of FIG. 4;  
         [0015]    [0015]FIG. 6 is a section taken along line C-C of FIG. 4;  
         [0016]    [0016]FIG. 7 is a side elevation showing a catheter according to a third embodiment of the invention;  
         [0017]    [0017]FIG. 8 is a section taken along line D-D of FIG. 7;  
         [0018]    [0018]FIG. 9 is a section showing a modification of the structure shown in FIG. 8;  
         [0019]    [0019]FIG. 10 is a side elevation showing a catheter according to a fourth embodiment of the invention;  
         [0020]    [0020]FIG. 11 is a side elevation showing a catheter according to a fifth embodiment of the invention;  
         [0021]    [0021]FIG. 12 is a section taken along line E-E of FIG. 11;  
         [0022]    [0022]FIG. 13 is a section showing a first embodiment of a lock mechanism;  
         [0023]    [0023]FIG. 14 is a section showing the lock mechanism of FIG. 13 in a locking state;  
         [0024]    [0024]FIG. 15 is a perspective view showing a tube to be used in the lock mechanism shown in FIG. 13;  
         [0025]    [0025]FIG. 16 is a perspective view showing a second mode of a lock mechanism;  
         [0026]    [0026]FIG. 17 is a side elevation showing a third embodiment of a lock mechanism;  
         [0027]    [0027]FIG. 18 is a section of the lock mechanism shown in FIG. 17;  
         [0028]    [0028]FIG. 19 is a side elevation showing a fourth embodiment of a lock mechanism;  
         [0029]    [0029]FIG. 20 is a section showing a fifth embodiment of a lock mechanism;  
         [0030]    [0030]FIG. 21 is a section showing a sixth embodiment of a lock mechanism; and  
         [0031]    [0031]FIG. 22 is a section showing a seventh embodiment of a lock mechanism. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]    In FIGS. 1 and 2, a catheter  10  is provided with an inner tube  11 . The leading end portion, as located at the lefthand end portion of FIG. 1 of the inner tube  11 , is suitably bent into a desired shape according to the related part (e.g., a blood vessel part to be inspected or treated) of a patient. On this inner tube  11 , there is fitted an outer tube  12  which is formed in a cylindrical shape so as to move freely in the axial directions. As will be described hereinafter, the inner tube  11  can turn integrally with the outer tube  12 . This outer tube  12  is equipped at its base end portion, as located at the righthand end portion of FIG. 1, with a grip member  21  to allow easy gripping of the catheter  10 .  
         [0033]    As clearly seen, especially from FIG. 2, the outer tube  12  has a round section, but a guide hole  13  extending axially through the outer tube  12  has a rectangular or square section. Thus, the inner tube  11  has a rectangular or square section dimensioned to leave a clearance  15  between the inner periphery of the guide hole  13  of the outer tube  12  and the outer periphery of the inner tube  11  which allows the inner tube to move axially through the guide hole  13 . By thus shaping the section of the inner tube  11  and the guide hole  13  of the outer tube  12 , the inner tube  11  and the outer tube  12  are turned together when either of them is turned. Therefore, it is necessary to maintain the accuracy of the clearance  15  to warrant a smooth movement of the inner tube  11  along the guide hole  13 . This accuracy of clearance is far better than when the inner tube  11  is enabled to turn without any friction within the guide hole  13 .  
         [0034]    The base end portion, as located on the righthand end portion of FIG. 1, of the inner tube  11  is adapted to be connected through a connector  90  to another tube  16 . This tube  16  is jointed to a syringe (not shown) so that a contrast medium, for example, is fed into an inner passage  17  extending axially in the inner tube  11 . As shown in FIG. 3, the catheter  10  is inserted into the body by a well-known method, and the inner tube  11  is then moved axially and turned so that the leading end portion of the inner tube  11  can be brought to a position near the part  18  to be inspected. At this position, the contrast medium, as having passed through the inner passage  17 , is fed from the leading end portion of the inner tube  11  to the part  18 .  
         [0035]    On the base end portion of the inner tube  11 , there is engraved or indicated a scale  19  which allows an easy determination as to how far the outer tube  12  has moved on the inner tube  11 . At the leading end portion of the inner tube  11 , on the other hand, there is mounted a soft tip  14 . This soft tip  14  softens as much as possible any impact when the leading end portion of the inner tube  11  comes into abutment against a blood vessel wall during the use of the catheter  10 . If the external diameter of the soft tip  14  is suitably adjusted, the outer tube  12  comes, when moved leftward, into engagement at its leading end portion (or its lefthand end portion) with the leading end portion of the inner tube  11  so that its further movement in the leftward direction is prevented. As a result, the movement of the outer tube  12  is confined between the connector  90  and the soft tip  14  so that the outer tube  12  is prevented from coming off the inner tube  11 .  
         [0036]    The inner tube  11  and the outer tube  12  may be identical in their materials and internal structures to those of the prior art. Specifically, the material can be exemplified by polyamide, polyurethane or polyethylene, or a mixture of the recited polymers as the case may be, such as when a higher bending strength or hardness is demanded. On the other hand, the internal structure may be exemplified by a single-layered tube or a two- or more-layered tube. In the latter case, a mesh of stainless steel or another metal may be sandwiched between the two adjoining layers. In order to observe the catheter clearly in an X-ray examination, the inner tube  11  (or the outer tube  12 , as the case may be) may contain a material such as an X-ray impermeable substance such as barium.  
         [0037]    In the catheter  10  thus far described, both the sectional shape of the guide hole  13  extending axially through the outer tube  12  and the sectional shape of the inner tube  11  are rectangular or square throughout the entire length to facilitate axial movement along the guide hole  13 . This structure is adopted because both tubes are turned simultaneously or integrally when either of them is turned. The invention should not be limited to this structure, but may adopt another structure as long as the simultaneous or integral turns of the tubes are ensured. As shown in FIGS.  4  to  6 , both the sectional shape of the guide hole  13  extending axially through the outer tube  12  and the sectional shape of the inner tube  11 , to facilitate axial movement along the guide hole  13 , are made partially rectangular or square. In the remaining portions, however, both the sectional shape of the guide hole  13  extending axially through the outer tube  12  and the sectional shape of the inner tube  11  may be made circular to move axially along the guide hole  13 . In this case, the sectional shape of the lefthand side of the outer tube  12  is also circular.  
         [0038]    On the outer circumference of the inner tube  11  having a round sectional shape, as shown in FIGS. 7 and 8, there is fixed a member  20  having keys  20   a  or an oval member  30  as shown in FIG. 9. The sectional shape of the guide hole  13  extending axially through the outer tube  12  is formed into a shape similar to that of the member  20  or the member  30  so that the inner tube  11  and the outer tube  12  can be turned simultaneously or integrally. In the device shown in FIG. 7, a grip member  21  is fixed on the inner tube  11 .  
         [0039]    In a bracket  40  arranged outside of the outer tube  12 , as shown in FIGS.  10  to  12 , there are formed a pair of slits  41  extending axially. A member  42  is comprised of two concentric rings connected by two radial ribs which are guided in the slits  41 . The inner ring is connected to the outer side of the outer tube  12 . Moreover, the bracket  40  is integrally connected at its righthand end portion with the connector  90 . By adopting this structure, by operating only the member  42 , the outer tube  12  and the inner tube  11  can be turned integrally and the outer tube  12  can be moved axially. The shape of the slit  40  should not be limited to the shown straight one but may be helical or stepped.  
         [0040]    On the outer tube  12 , as shown in FIG. 13, there are integrally formed a pair of projections  51 . On the outer tube  12 , there is also a ring member  52  which is made axially movable relative to the tube  12 . When the ring member  52  moves axially toward the projections  51  and rides on them, as shown in FIG. 14, the outer tube  12  is radially reduced to clamp onto the inner tube  11 . Thus, the inner tube  11  is locked by a lock mechanism  53  which is composed of the ring member  52  and the paired projections  51 , so that the outer tube  12  can be fixed at an arbitrary position.  
         [0041]    The lock mechanism for fixing the outer tube  12  at an arbitrary position relative to the inner tube  11  may be exemplified by a tube  55  which is made of an elastic material and has an expansion slot  54 , as shown in FIGS. 15 and 16.  
         [0042]    A second example of the lock mechanism  53  is shown in FIG. 17. In the structure shown in FIGS.  10  to  12 , a pair of wedges  56 , formed on the opposite sides of the member  42 , are fitted in the slits  41 .  
         [0043]    A third example of the lock mechanism  53  is shown in FIGS. 18 and 19. In the structure shown in FIGS.  10  to  12 , the wedges  56 , as formed integrally with a moving member  50 , are fitted axially in the inner circumference of the member  55  which is fixed on the bracket  40 .  
         [0044]    A fourth example of the lock mechanism  53  is shown in FIG. 20. In the structure shown in FIGS.  10  to  12 , a cylindrical portion  43  having an expansion slot  42   a  is made integrally with the member  42 . A nut member  60  fitted on the cylindrical portion  43  is fastened on a threaded portion  61  of the cylindrical portion  43 . The cylindrical portion is radially reduced, as shown in FIG. 21 as a result of a camming action by the nut member  60 , to grip the tube  12  to prevent the member  42  from moving on the bracket  40 . As a result, the outer inner tube  12  is locked.  
         [0045]    The bracket  40  shown in FIGS.  10  to  12 , is shown in FIG. 22 and is provided with an elastic joint  70  which is interposed between the bracket  40  and the outer tube  12  to prevent the catheter  10  from being damaged when bent.  
         [0046]    While the preferred embodiments have been described, variations thereto will occur to those skilled in the art within the scope of the present inventive concepts which are delineated by the following claims.