Abstract:
The catheter coupling is intended for providing the proximal end of a catheter with a plug connector forming a fluid transfer connection. The catheter coupling comprises two pivotable jaws enclosing a wavy channel. One of the jaws is provided with a hose in which the catheter may be inserted. When the other jaw is closed, the hose and the catheter is deformed to a wave-shape without any significant change in cross section. Thus, the catheter is secured against being pulled out.

Description:
BACKGROUND OF THE INVENTION 
     The present invention refers to a catheter coupling with integrated strain relief for allowing a catheter to be coupled to a syringe or to another liquid transfer device. 
     In epidural anesthesia, a catheter is introduced into the epidural space of a patient through a steel cannula. Subsequently, the steel cannula is withdrawn beyond the proximal catheter end, whereas the catheter remains in its position. The proximal end of the catheter must not have any enlargements or connecting devices, since the withdrawal of the steel cannula would be hindered thereby. After removal of the steel cannula, the catheter must be provided with a catheter coupling, e.g. in the form of a Luer-Lock connector, for connection to liquid supplying device. The catheter consists of a flexible hose with a small diameter. The outer diameter is generally less than  1  mm. A catheter coupling connected to the catheter must not squeeze the catheter so that the catheter lumen stays open. 
     From EP 0 415 665 A1, a catheter coupling is known, wherein the catheter is passed through an annular elastomer plug clamped between two screwed elements. By tightening the screw elements, the plug is rotated radially and pressed against the catheter with force. To operate the catheter coupling, two hands are required, while having to hold the catheter at the same time. An appropriate tightening of the catheter coupling would thus require three hands. More-over, the tightening requires great strength. When the catheter coupling has a Luer-Lock connector having to be turned for disengagement, there is a risk that the catheter coupling is opened instead of the Luer-Lock connector so that the catheter slips out. 
     Another hose coupling is described in U.S. Pat. No. 5 423 766. Here, the catheter coupling includes a trumpet-shaped tube member, the catheter being slipped onto the narrower end thereof. Subsequently, the clamping is performed with two clamping members tensioned by means of a bayonet catch. Again, inadvertently turning the bayonet catch may cause disengagement. 
     A catheter coupling with two articulated jaws is known from U.S. Pat. No. 4 006 744. Here, one of the jaws is provided with a hose piece through which the catheter is passed. The other jaw is folded over the hose piece, clamping the same. The catheter is held only by the radially pressed hose piece. In this case, there is a risk of inadvertently pulling out the catheter. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a catheter coupling with strain relief that is simple to apply to the catheter and guarantees a great holding force, without constricting the catheter. 
     According to the present invention, the jaws extend in the longitudinal direction of the hose piece receiving the catheter end and they are connected at the one end of the hose piece by a joint whose axis extends transversely to the hose piece. At the opposite end the jaws may be locked in the closed state. Thus, the end portion of the catheter to be clamped is engaged by the jaws in the longitudinal direction, thereby guaranteeing a-particularly good and safe hold, since a long covered portion can be realized. Further, when closing the jaws, the clamping force progressively increases from one end to the other. In this manner, a safe clamping is achieved over a relatively long distance. 
     Preferably, the grooves in the jaws that form the channel, does not have a continuous groove bottom, but the groove bottom has rises and indentations, to cause a wavy path of the hose piece when the jaws are closed. This generates high frictional resistance. 
     The catheter coupling is very easy to handle. It is only necessary to press the jaws against each other to close the channel. Moreover, there is no risk of the catheter coupling being inadvertently opened by turning movements as they are necessary for disengagement from a counter plug connector. 
     Preferably, the channel has at least two bends with a straight section in between. Here, the hose is deformed only in the bends, but not in the straight portion. This way, it is made sure that, with the jaws open, the hose assumes a stretched straight state so that the catheter can easily be introduced into the hose. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following is a detailed description of embodiments of the present invention with reference to the drawings. 
     In the Figures: 
     FIG. 1 is a side elevational view of the catheter coupling, 
     FIG. 2 is a front end view in the direction of the arrow II in FIG. 1, 
     FIG. 3 illustrates the catheter coupling with the jaws open, 
     FIG. 4 is an enlarged plan view in the direction of the arrow IV in FIG. 1, 
     FIG. 5 is a view similar to FIG. 1 with the hose being shown, 
     FIG. 6 is a longitudinal section through the open jaws with the hose arranged therebetween and the catheter illustrated below, 
     FIG. 7 is a sectional view along line VII—VII in FIG. 5, 
     FIG. 8 is a sectional view along line VIII—VIII in FIG. 5, 
     FIG. 9 illustrates another embodiment, 
     FIG. 10 is a longitudinal section through the lower jaw of the catheter coupling of FIG. 9, 
     FIG. 11 is a sectional view along line XI—XI of FIG. 9, and 
     FIG. 12 is a sectional view along line XII—XII of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The catheter coupling illustrated comprises two elongate substantially plate-shaped jaws  10 ,  11  connected at one end by a joint  12 . The jaw  10  forms a base jaw rigidly connected with the connecting member  13  and projecting the same axially, whereas the jaw  11  can be folded open, as illustrated in FIG.  3 . 
     At the end averted from the joint  12 , the jaw  10  has an end wall  14  with a throughgoing opening  15  for insertion of a catheter. A guiding funnel  16  is formed around the opening  15 . 
     The jaws  10 ,  11  have interlocking lock elements  17 ,  18  at the end averted from the joint  12 . The lock element  17  consists of a recess at the jaw  10  and the lock element  18  is a resilient hook engaging the recess when the jaw is closed. 
     At its two sides, the jaw  10  has wavy edges  19  and the jaw  11  has matching wavy edges  20 . In the closed state of FIG. 1, the edges  19  and  20  abut in a mating manner, whereas the lock elements  17 ,  18  at the ends of the edges are interlocked. 
     When closed, the jaws  10 ,  11  form a longitudinally extending channel  21  that is straight in plan view, as illustrated in FIG. 4, and extends from a passage  22  at the connecting member  13  to the end wall  14 . This channel  21 , shown dotted in FIGS. 3 and 4, has two bends  23 ,  23   a , as illustrated in the side elevational view of FIG.  5 . Both bends extend in the same direction, i.e., in the present case, into the jaw  10 . Thus, in the bends  23 ,  23   a , the channel  21  runs through a depression, respectively. In the section  24  between the bends  23 ,  23   a , the channel  21  is straight and extends axial to its end portions. The bends  23 ,  23   a  and the straight portion  24  each have about the same length. The channel  21  is circular in section. It is formed from a semi-circular groove  21   a  in the upper jaw and a semi-circular groove  21   b  in the lower jaw. 
     The channel  21  contains a hose piece  25  extending from the passage  22  to the opening  15 . The ends of the hose piece  25  may each be glued to the body of the jaw  10 . The hose piece  25  is an integral part of the catheter coupling. 
     When the jaw  11  is opened, the hose piece  25  associated to the jaw  10  takes a straight shape, as illustrated in FIG. 6, lifting itself from the bottom of the two bends  23 ,  23   a . The bottom of the groove  21   a  of the upper jaw  11  is provided with two rises  26 ,  27 . The bottom of the groove  21   b  is provided with corresponding recesses  46 ,  47 . 
     FIG. 6 illustrates the opened state of the jaws. In this state, the proximal end portion of the catheter  30  is inserted into the hose  25  through the opening  15  until the catheter tip  31  is in the passage  22 . 
     The connecting member  13  is made of transparent plastic material. The outer surface of the connecting member is formed with a lens  36  through which the passage  22  can be seen enlarged. Thus, it is easily determined whether the catheter tip  31  is in the appropriate position. 
     The connecting member  13  is a Luer-Lock plug connector  33  with an inner cone  34  and thread-like projections  35  on its outer surface. The plug connector  33  is plugged with a complementary counter plug connector for connecting the catheter  30  with a liquid source, e.g. via a filter. 
     It can be seen in FIGS. 7 and 8 that the channel  21  has a constant cross section of the same size in the straight sections  24 , as well as in the bends  23 ,  23   a . When the jaws  10 ,  11  are closed, the hose piece  25  is slightly pressed so that it firmly embraces the catheter  30 . The strain relief of the catheter is obtained by pressing the hose piece and the catheter therein into the bends  23 ,  23   a  of the channel  21 . 
     While, in the embodiment illustrated, the bends extend perpendicular at two locations in the groove bottom, escape openings  41 ,  42  are provided into which the soft material of the hose piece  25  may escape when the upper clamping jaw is closed. 
     In the embodiment of FIGS. 9-12, the lower and the upper jaws  10   a ,  11   a  are also connected by a joint  12 . The opposite ends of the jaws  10   a ,  11   a  are provided with lock elements  17 ,  18  locking the two jaws relative to each other when the upper jaw  11   a  is closed. For clarity of illustration, the hose piece  25  is not illustrated for the second embodiment. The groove  21  receiving the hose piece  25  has a straight groove bottom  40  without rises or depressions. The groove  21   b  is generally semi-circular in cross section. At two locations in the groove bottom, escape openings  41 ,  42  are provided into which the soft material of the hose piece  25  may escape when the upper clamping jaw is closed. 
     As in the first embodiment, the groove bottom of the upper jaw  11   a  is provided with raised portions  26  and  27  separated by a straight section. These raised portions each cause a local squeezing on the straight groove bottom  40  of the lower jaw  10   a  and of the catheter within the hose piece. The raised portions  26 ,  27  thus compress the hose piece  25 . 
     The channel  21  is defined circumferentially by the two opposed grooves  21   a  and  21   b . As illustrated in FIGS. 11 and 12, one groove  21   a  is provided with longitudinal projections in the form of triangular bars. The opposite groove  21   b  has corresponding recesses  44  into which the projections  43  enter when the jaws are closed. Although the parting plane of the jaws  10   a ,  11   a  extends diametrically through the channel  21 , the upper jaw  10   a  embraces more than half of the channel circumference with its longitudinal projections  43 , while the lower jaw  11   a  defines less than half the channel circumference because of the recesses  44 . The projections  43  prevent the material of the hose piece (not illustrated) within the channel  21  from creeping into the gap between the two jaws. Further, when closing the jaws, a precise guiding is guaranteed. 
     In the second embodiment, raised portions  26 ,  27  are provided only at the upper jaw  11   a  so that the cross section of the channel  21  is reduced at the locations of the raised portions  26 ,  27 . At these locations, the hose piece is squeezed.