Patent Publication Number: US-2022218946-A1

Title: Push device for the axial insertion of an elongate, flexible body

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 16/507,782, filed Jul. 10, 2019, now allowed, which is a continuation of U.S. patent application Ser. No. 13/261,735, filed Oct. 15, 2013, now U.S. Pat. No. 10,391,278, which is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/EP2012/001062, filed Mar. 6, 2012, published as International Publication No. WO 2012/119782 A1, which claims the benefit of U.S. Provisional Application No. 61/451,222, filed Mar. 10, 2011, and claims priority from European Patent Application No. 11075043.7, filed Mar. 10, 2011, the disclosures of which are hereby incorporated herein by reference. 
    
    
     The invention lies in the field of mechanics, in particular of mechanical engineering and precision technology. It concerns those mechanical problems which arise on inserting a flexible, elongate body into an opening or sheath, due to its tendency to buckle. To buckle in the context of the present invention is also to be understood as to abruptly bend, and could also be described as kinking in a two-dimensional manner, in accordance with the German word “knicken”. 
     Such flexible, elongate bodies may for example be cables, wires, threads, flexible tubings or a combination of such elements, which are typically to be inserted into sheaths or openings, tubes, hoses or generally cavities. Such an elongate body may also be a second sheath which is inserted into a first sheath or is to be held in a stationary manner with respect to this. If a resistance against a further pushing movement results when pushing such bodies, then the body must be prevented from buckling, in order to permit a further push movement, or corresponding radial deflection movements must be limited. 
     As a whole, amongst other things, it is case of designing the handling such that it is secure as possible. Thereby, it is advantageous if on introduction, a certain buckling angle is not exceeded and a certain bending radius is not fallen short of. 
     One application of the invention for example results on introducing a mechanical pipe cleaning device into a pipe conduit system, wherein the cleaning device is inserted with a flexible shaft. 
     Typically, such problems also result in medical technology, if for example a cannula or a catheter is to be inserted into a body opening, a lumen of the body or an artificial lumen. 
     Typical such situations are for example evident from the international patent application WO 02/43791 A1. There, it is described that an intravascular pump is introduced into a sheath, in order finally to be inserted it into a blood vessel of a human body. A further push movement takes place, also after the pump has passed the actual sheath region. 
     Since such pumps are to be pushed through a blood vessel over lengths of a few tens of centimeters within the body, one must reckon with a certain push resistance which renders necessary a certain push force on inserting. In particular with self-openable or self-expandable pumps heads, one is to reckon with an increased push resistance on account of the occurring restoring forces of the folded or compressed pump head. This is particularly due to the fact—that because with such pumps, a flexible shaft which is envisaged for high rotation speeds and a long service life and which is sensitive to buckling runs within a catheter to be pushed, it must be ensured that the necessary push force may be applied onto the catheter without this buckling out or deflecting in another manner. 
     It is therefore the object of the present invention, to provide a push device for the axial insertion of an elongate, flexible body into a sheath or for the secure mounting of such a body with respect to a sheath, which is constructed in an as simple as possible manner and which permits the simple production of a push movement and reliably prevents a deflection of the elongate body. 
     According to the invention, this object is achieved with the features specified in patent claim  1 . 
     A holding unit is provided for this, which may be designed as an axial force introduction unit which by way of a non-positive or positive fit, exerts an axial holding force or push force onto the elongate body and which is arranged in a stationary manner relative to the sheath or is led on a defined movement path. Axial direction in this context is to be understood as the longitudinal axis direction of the sheath and/or the elongate body. 
     Since one may not often engage directly on an end of the elongate body, an axial force introduction unit must engage on the elongate body either by way of clamping, i.e., non-positive fit and corresponding static friction forces, or by way of a positive fit on the elongate body, inasmuch as this comprises suitable shape elements on the outer side. A corresponding clamping or a positive fit then permits the application of an axial force and thus a holding force and a push movement. For example, one may envisage the (first) sheath as well as the elongate body which indeed may also be formed as a (then second) sheath, each comprising a flange as a fit piece, wherein each of the flanges may be each inserted into a recess of the push device, or both flanges together maybe inserted into a single recess of the push device, in particular of the holding unit or of a guide device for the holding unit which may then be fastened on the sheath, said insertion being such that the flanges are fixed in the axial direction and/or radial direction. 
     Advantageously, the fit piece of the sheath is not displaceable in the push device, disregarding the necessary mechanical play. 
     The fit piece of the sheath may advantageously be rotatable about the insert direction of the push device in different positions, in particular with a cylinder-symmetrical design may also be inserted into the recess at any angular position. 
     After inserting the fit piece into the recess, this fit piece may either still be freely rotatably about the insert direction or also be non-positively fixed or positively fixed with respect to the rotation angle. 
     The push device may be able to be dismantled for inserting the flange or flanges into the recess or recesses and for example be designed as a longitudinally divided hollow body, in particular hollow cylinder. The recess may also comprise a rinsing device, so that a rinsing fluid for cleaning the fit piece/pieces may be introduced there from the outside through a channel. 
     Due to the fact that the holding unit/axial force introduction unit is arranged in a stationary manner to the (first) sheath, in the push device, the distance and the alignment of the unit may be selected such that the axial loading of the elongate body is well controllable and is easy to limit, that only safe radial forces and radial deflections are applied onto the elongate body and that the free length of the elongate body between the axial force introduction unit and the sheath may be defined or limited. 
     Even if the axial force introduction unit is led on a defined movement path, this path may be accordingly selected such that the tendency of the elongate body to break out laterally given a push movement is minimized. Moreover, a mechanical guide for the elongate body may be well dimensioned and positioned with a given movement path of the axial force introduction unit. 
     The guide of the axial force introduction unit may for example be realized by way of a single-stage or multi-stage telescopic guide, for example with concentric tubes, or by way of guiding in a rail or in a cylindrical cavity. 
     Advantageously, one may envisage the push device being mechanically coupled onto the sheath in a direct manner. This for example may be achieved by way of a central thread, a bayonet closure, by the application of adhesion forces, by way of a magnetic coupling, by way of an eccentric screw connection (for example by way of screws distributed on the periphery), by way of gluing, by way of electrostatic attraction forces, by way of elastic holding elements such as springs, clips or rubber cords or by way of insertion of a fit piece of the sheath into a fittingly shaped recess of the holding unit. 
     In particular, a deflection of the elongate body on entry into the sheath should be avoided, since a mechanical guiding and radial support is usually given or may be simply created in the sheath or in the flexible tube belonging to the sheath, and the risk of buckling plays less of a role behind the sheath or the flexible tube belonging to the sheath, on account of the reduced restoring forces. 
     By way of coupling the push device onto the sheath, the distance between the holding unit/axial force introduction unit and the sheath is limited, and a defined guiding of the elongate body and/or a radial supporting is made possible. Also, it is particularly simple to fix the movement path of the axial force introduction unit, in the case that such is provided, with respect to the sheath. 
     For coupling, the sheath may for example comprise a flange or a plane front plate with an opening, into which the elongate body is to be introduced, wherein a corresponding counter flange of the push device may be coupled onto the front plate or the flange. Thereby, usually releasable connection techniques may be applied or also the usual joining techniques such as gluing or other adhesive measures, which advantageously however are to create a releasable connection. 
     If by way of the push device, only the first sheath and an elongate body, for example a second sheath, are to be axially pressed against one another, then a flange or a front plate of the first sheath on the one hand and a flange of the second sheath or of another elongate body may be fixed to one another. However, for example a connection may also be created by way of insertion into one another, which is held by a non-positive or positive fit. What is important here, is that the forces for holding the connection are greater than the forces which are necessary for pushing the elongate body, so that the connection is not unintentionally released on pushing the elongate body. 
     A mechanical coupling may advantageously also be provided directly between the axial force introduction unit and the sheath. A radial guiding between the axial force introduction unit and the sheath may be minimized or completely left out by way of this. The constructional size of the push device may thus also be kept very low. 
     Advantageously, the push device may comprise a guide device which may be fastened on the sheath by way of a coupling and which radially supports the elongate body, wherein the axial force introduction unit is arranged either in a stationary manner relative to the guide device or is guided on a defined movement path. In this case, the guide device is provided between the axial force introduction unit and the sheath and either serves for bridging a distance between the axial force introduction device and the sheath, and with this rendering the application of a push force manageable, and/or with a given small distance between the axial force introduction unit and the sheath, to design this distance by way of the guide device, in a manner such that the elongate body may in no case radially deflect with this distance. 
     The axial force introduction unit may advantageously comprise a radial clamping device which by way of pressing a clamping tool onto the elongate body in the radial direction produces a bond which serves for applying a push force or holding force in the axial direction. The clamping tool may be designed in a movable manner for example and roll on the elongate body. 
     In particular, at least one, on particular two, three or four friction wheels may be provided as a clamping tool, which lie radially opposite one another at least partly with respect to the elongate body. The elongate body may then be clamped between the friction wheels and be radially supported by these. A push movement may be applied onto the elongate body by way of a drive of the friction wheels. One may also arrange several sets of friction wheels or knurled wheels one after the other in the longitudinal direction of the elongate body. 
     One may also envisage the friction wheels or at least one of them comprising a freewheel means which permits a rotation in each case in only one direction, so that for example the friction wheels block and push the elongate body upon advancing the push device, and rotate the friction wheels in a manner such that the push device may be displaced with respect to the elongate body without force, upon retracting the push device. With this, the elongate body may for example be pushed in steps, for example by hand or by way of another drive, by way of displacement of the push device. 
     Such drives may for example be provided by way of electric motors on the friction wheels, so that the push device may stand still in a stationary manner. A reduced space requirement results with the application of the push device by way of this. 
     Generally, it may a make sense for the friction wheels to be able to be controlled with regard to their rotation, i.e., either be actively drivable or for example lockable in a controlled manner from the outside. The continuous drive of the push device by way of a rotation drive of the friction wheels for example also permits the control of the introduced push force in dependence on the advance, the advance speed or a detected counter-force. With this, one may prevent a catheter for example, which is inserted into a body, from being simply pushed further in the case that an increased resistance arises due to hitting a vessel wall. A suitable control may stop the advance procedure or slow it down. A suitable control which may designed in an electronic manner, may either control the advance force or the advance speed either according to a defined curve/characteristics or in dependence on the push resistance. 
     One may also advantageously envisage the clamping tool being provided with clamping jaws radially on both sides of the elongate body, and the clamping jaws with the elongate body fixed between them being movable in a guided manner with respect to the sheath and/or a guide device, essentially in the axial direction the elongate body. 
     The clamping jaws may thereby be designed as two or more bodies which are movable relative to one another in the radial direction with respect to the elongate body, and which for example may also be designed in a compliant manner, in particular softer that the elongate body itself. For this purpose, the clamping jaws should consist of a soft material such as plastic or elastomer for example or a coated with such a material. One may also envisage only a few of the clamping jaws being designed in a movable manner, whilst the other clamping jaws are fixed in a stationary manner. 
     For example, two, three, four, five or more clamping jaws may be provided, which lie opposite one another on the periphery of the elongate body. 
     Particularly advantageously, the clamping jaws may be formed by two or more parts for example of a hollow cylinder or of any other shape corresponding to the elongate body, said shape receiving the elongate body. The clamping jaws may then form sector bodies of the hollow cylinder. A hollow cylinder in this context is to be understood as a body which has an in particular cylindrical, continuous opening. Such a body may for example also have a cylindrical shape on its outer side. Instead of a hollow cylinder, one may also apply a different type of body with a continuous opening. 
     The respective sector bodies may for example have the same length as the hollow cylinder and be distributed on the periphery of the elongate body. The push device may also be designed in a manner such that first clamping jaws are arranged in a non-movable manner in the axial direction and consist of a material which has a low friction compared to the material of the elongate body. Second clamping jaws in contrast are axially movable and have a greater friction coefficient compared to the material of the elongate body, so that the elongate body may be pushed by the second clamping jaws against the first clamping jaws and may be slidingly moved in the axial direction on these, as on a guide rail. In this manner, the radial guiding for the elongate body may be realized by the clamping jaws, as well as the advance in the axial direction by way of individual ones of the clamping jaws. 
     The holding device may comprise a clamping device for the elongate body, said clamping device able to be clamped by hand by way of radial pressure and releasing the elongate body with the absence of an external pressure force. Spring elements may serve for this, which automatically opens the holding device/clamping device. 
     A method for realizing the invention envisages the speed of the advance of the elongate body being controlled by a control device. Thereby the speed may be activated as a constant speed or also according to defined speed characteristics/time characteristics or speed characteristics/displacement characteristics. 
     If unforeseen resistances to the elongate body result with the advance movement, for example if this is inserted into a blood vessel of a patient, then the respective drive force may be increased by way of the control, in order to ensure the advance speed according to the defined characteristics. 
     However, one may also envisage a control which keeps the advance resistance or the advance force constant, so that the drive force onto the push device is reduced with the occurrence of increased push resistances on the elongate body, for example in order to prevent a buckling of the elongate body due to the increase of push forces, or with a medical application, for example if the elongate body is a catheter which is introduced into a body opening, to prevent an injury of the patient. In this case, the advance may also be completely stopped by way of the control, and the elongate body retracted a little. The increase of the push resistance may be signaled by a light on the outside on the push device as well as by way of an acoustic signal transducer. 
     Inasmuch as this is concerned, the push resistance may be measured and the push movement may be controlled with or without a closed loop in dependence on the push resistance. For this, a drive, for example an electric or pneumatic drive, and a suitable sensor, for example a current sensor for measuring the magnitude of the applied current strength, a voltage senor or a suitable pressure sensor with the use of pneumatics, as well as a control device and correspond signal transducers are to be provided for this. 
    
    
     
       The invention is hereinafter shown by way of one embodiment example and described hereinafter. Thereby are shown in: 
         FIG. 1  the application of a heart catheter pump with a human heart, 
         FIG. 2  a pump device with a heart catheter pump and with a drive shaft which runs in a hose-like casing, 
         FIG. 3  a push device in a three-dimensional view, 
         FIG. 4  the push device of  FIG. 3  in a lined representation, 
         FIG. 5  a longitudinal section through the device of  FIG. 4 , 
         FIG. 6  a guide device designed as a hand grip, in a longitudinal section with the front end of a sheath, 
         FIG. 7  a guide device without an inserted sheath, 
         FIG. 8  the guide device of  FIG. 7  in a front view, 
         FIG. 9  a push device with at least two friction wheels, 
         FIG. 10  a plan view of the device according to  FIG. 9 , along the line indicated in  FIG. 3  at IV-IV, 
         FIG. 11  a similar view to that in  FIG. 10 , with four friction wheels distributed around the elongate body, 
         FIG. 12  a similar view as in  FIG. 11 , additionally with electromechanical drives of the friction wheels, 
         FIG. 13  an arrangement with two friction wheels which have friction surfaces which are concave in cross section, 
         FIG. 14  a push device similar to that of  FIG. 9 , with which the friction wheels only serve for the radial support and a different type of axial force introduction is envisaged, 
         FIG. 15  a view of the device of  FIG. 14  along the line which is characterized there at IX-IX, 
         FIG. 16  a further variant of the axial force introduction unit, 
         FIG. 17  a cross section of the axial force introduction unit of  FIG. 16 , 
         FIG. 18  a further design of the axial force introduction unit, 
         FIG. 19  a cross-sectional view along the line XIII-XIII of  FIG. 18 , 
         FIG. 20  another variant of the axial force introduction unit of  FIG. 18 , 
         FIG. 21  in a longitudinal section, a push device with axially stationary and axially movable clamping jaws, 
         FIG. 22  a cross section of the device of  FIG. 21  along the line characterized there at XVI-XVI and 
         FIG. 23  a detail of the drive device for a push device. 
     
    
    
       FIG. 1  in a longitudinal section shows a blood vessel  1  with a first sheath  2  in the form of a flexible tubing or hose and which with its distal end projects into the blood vessel  1  in the direction of a heart chamber  3  up to the aortic arch. The sheath  2  is introduced through an opening  4  into the blood vessel  1  and is ideally sealed there. The first sheath  2  at its proximal (outside the body) end  5  comprises a flange  6 . 
     A heart catheter  8  which is designed in a hollow manner and in which a drive shaft for a heart pump  9  which is represented in a dashed manner, is shown at the distal end  7  of the sheath  2 , also in a dashed manner. The pump  9  is inserted into the heart chamber  3  and comprises a rotor which rotates with a high rotation speed, driven by the shaft, in order to deliver blood out of the heart chamber into the blood vessel  1 . 
     An elongate body  10  is represented at the proximal end  5  of the sheath  2 , in front of the flange  6 , and is to be introduced into the sheath  2  in the direction of the arrow  11 . The elongate body  10  is shown only in sections there. In the shown case, the elongate body is formed for example by way of the heart catheter  8  which together with the flexible drive shaft arranged therein represents a flexible elongate body which is to be pushed through the sheath  2  into the blood vessel  1  and further into the heart chamber  3 . Depending on the point, at which the heart catheter is inserted into a blood vessel (typically at a femoral artery), the advance displacement for the catheter is more than 80 cm in the patient body. 
     The elongate body  10  may consist of a heart catheter  8  which is surrounded by a second, flexible-tube-like sheath. This second sheath is then designed such that it keeps the radially compressible pump compressed. The second sheath may usefully already be premanufactured with the heart catheter  8  and the pump before use on a patient body. 
     The second sheath may then be axially held onto the first sheath and fixed there, for example by way of the push device according to the invention. Whilst the second sheath is pressed axially against the first sheath, the heart catheter may then be pushed through the second sheath into the first sheath and by way of this may be pushed into the blood vessel. 
     A push device according to the invention may likewise be applied with the axial insertion of the heart catheter into the second sheath. This push device is then applied onto the second sheath opposite to the first sheath and encloses the section of the heart catheter in front of the second sheath. 
       FIG. 2  shows a more detailed, but schematic representation of the pump catheter  8  with the flexible drive shaft  12 . This is connected proximally to a drive in the form of a motor  13  and distally to a drive hub  14  within a pump housing  15 . The hub  14  carries rotor blades  16  for delivery of a fluid or blood. 
       FIG. 3  shows one design of a push device in a three-dimensional view. 
       FIG. 4  shows the same view as an outline drawing and  FIG. 5  a longitudinal section. 
     A guide device  56  in the form of a hollow cylinder divided into two, with a lower half  57  and with an upper half  58  is shown. The cylindrical cavity  59  receives the elongate body  60  to be pushed, as well as a second sheath and supports it in a radial manner. The upper half  58  is connected to the lower half  57  via screws  61 ,  62  which slide in elongate holes. The elongate holes are widened at one end, so that the upper half may be removed after displacing this. By way of this, the elongate body with the second sheath, just as the first sheath, may be inserted with its flange  64  without any problem, and the front-side end  63  of the sheath (cf.  FIG. 6 ) in particular the flange  64  may be inserted into the undercut cavity  67  of the hollow cylinder  56  ( FIGS. 6, 7 ). A reliable, releasable coupling of the guide device onto the sheath is ensured by way of this. A channel of a rinsing device which runs out into the cavity  67  is indicated in  FIG. 5  with the reference numeral  66 . 
     A holding unit/axial force introduction device may comprise recesses for tear tabs  65  of a second sheath, if the second sheath is designed as a so-called “peel-off sheath”. This means that the second sheath on account of its material structure (molecular alignment, anisotropic structure) and/or the incorporation of predefined breakage locations (perforation), is set up to be longitudinally torn open and removed, after pushing through a heart catheter. 
       FIG. 8  shows a further illustration of a cross section of  FIG. 6 . 
       FIG. 9  specifically shows another embodiment of an advance device, wherein the flange  6  of the first sheath  2  is shown on the left side and the push device in the right region of the figure. The push device comprises a tubular housing  17  whose distal end  18  may be pushed onto the flange  6  and is fixed there with respect to the flange  6 . The fixation may for example be realized by way of a central thread on the flange  6  as well as on the housing end  18  or by way of a bayonet connection between these parts. Other types of screw connections or and other bonding connections such as gluing or magnetic bonding are conceivable. It makes sense if the 
     connection between the push device and the flange  6  of the sheath can be easily released again. The push device may also comprise a cavity for receiving and fixing the flange  6 , as well as an opening for incorporating the flange into the cavity, 
     At least two friction wheels  19 ,  20  as part of an axial force introduction device or holding unit are rotatably mounted within the housing  17  and on their periphery, each have a friction coating  19   a ,  20   a  which has a greater coefficient of friction compared to the material of the elongate body  10 . The elongate body  10  is typically clamped in between the friction wheels  19 ,  20 . The elongate body may thereby be a catheter as well as a second sheath. 
     The friction wheels  19 ,  20  may for example be controllable with regard to the rotation ability. If they are blocked, as a whole the elongate body may be advanced in the direction of the arrow  21  by way of axial movement of the push device together with the friction wheels if these are movable in a guided manner in the housing  17 . If the push device is retracted opposite to the direction of the arrow  21 , then the friction wheels  19 ,  20  may be released for example by way of a control or a freewheel, so that with this movement of the push device, the elongate body  10  is not caught, but remains in the position relative to the sheath  2 . The friction wheels  19 ,  20  may be blocked again before a renewed advance of the push device in the direction of the arrow  21 . For example, for realizing such a drive mechanism, the housing  17  may be axially advanceable and retractable on a connection of the flange  6 . 
     Another variant of the drive may envisage the friction wheels  19 ,  20  being able to be driven in the direction of the arrows  22 ,  23  when the push device is stationary, in order to push the elongate body  10  in the direction of the arrow  21 . This variant has the advantage that the speed of the friction wheels  19 ,  20  or the torque may be detected for example by way of the current of an electric motor driving the friction wheels. The respectively detected variables may be used for controlling the advance speed of the elongate body or for the control of the push force, in order to limit this and thus to prevent injuries on inserting a catheter into a lumen within a body of a patient. Alternatively, the push force may also be limited by way of a slip coupling for example. 
       FIG. 10  in a plan view along the line IV-IV according to  FIG. 3  shows the two friction wheels  19 ,  20  as well as the elongate body  10  which is clamped between them. 
     In  FIG. 11  it is shown that indeed also more than two, for example four friction wheels  19 ,  20  may be provided distributed on the periphery of the elongate body. This may be three, five or six friction wheels for example. 
     A rotatable mounting is represented schematically for each individual friction wheel by way of a stylized pivot. The friction wheels may be drivable for example by way of individual motoric drives or together via a coupling gear. One may also envisage only individual ones or only a single one of the friction wheels being drivable. The other friction wheels in this case would automatically co-rotate with the drive of a single friction wheel. 
       FIG. 12  shows an example of an implementation of a drive via two electric motors  24 ,  25 . 
     Two friction wheels are represented in the  FIGS. 4 to 6  schematically as cylindrical wheels, as the case may be with a friction coating. 
     In contrast to this design, a concave outer peripheral surface of the friction wheel  19 ′,  20 ′ may also be provided according to  FIG. 13 . The concave surfaces  26  are designed in a manner such that they snugly bear on the elongate body  10  and also hold this laterally, so that one may ensure a reliable radial guiding of the elongate body already with two friction wheels. 
       FIG. 14  shows an advance device with an axial force introduction unit  27  in the form of a push cylinder  28  which on a guide body  29  is displaceable to and fro in the direction of the arrow  30 . The push cylinder  28  at one end comprises a bead-like disk  31  with a centric opening which is surrounded by a peripheral, movable lip  32 . The opening is dimensioned in a manner such that the edge of the lip  32  lies on the elongate body  10 . If the push cylinder  28  is pushed to the sheath  2 , then the lip  32  is deflected in the direction of the arrow  33 , and the centric opening of the bead disk  31  reduces in size and clamps the elongate body  10 . This is then caught in the direction towards the sheath  2  and is displaced to there. 
     With a withdrawal movement of the push cylinder  28 , the lip  32  moves in the direction of the arrow  34 , so that the centric opening of the bead disk  31  is enlarged and the push cylinder  28  may be retracted with respect to the elongate body  10  which remains stationary. 
     In this manner, the elongate body  10  may be moved into the sheath  2  in steps. The movement of the push cylinder  28  is guided on the guide body  29 , so that the movement path of the axial force introduction unit is fixed. The elongate body moreover is led in a cylindrical opening  35  of the guide body  29  and further in the direction of the sheath  2  through two or more friction wheels  19 ,  20  which are movable in a freely rotatable manner and lie opposite one another. A guiding by way of several groups of friction wheels, said groups lying axially behind one another, may be provided on the one hand, or exclusively by way of a long, hollow-cylindrical opening up to the flange  6  of the sheath  2 . 
     Opposite the flange  6  of the sheath  2  lies a similarly constructed flange  36  of the guide body  29 , so that the two flanges  6 ,  36  may be connected to one another by way of a screw connection which is shown by way of example by way of a dashed line  37 . For this, several screws may be distributed on the periphery of the flange, in particular in a symmetrical manner. 
     A cross section along the section line IX-IX in  FIG. 14  is represented in  FIG. 15 , with the centric opening  15  in the guide body  29  which is surrounded by the cylinder  28  of the axial force introduction unit  27 . 
       FIG. 16  shows another variant of an axial force introduction device which may be used for example in the push device according to  FIG. 14  instead of the axial force introduction device  27 . A push cylinder  28 ′ is shown in  FIG. 16 , which may be guided in an axial manner on the guide body  29 . A foam body  38  serves for clamping in the elongate body  10  and may be pressed together radially by way of pressure in the direction of the arrows  39 ,  40 , in order to compress the opening  35 ′ and to firmly clamp the elongate body in the opening  35 ′. For example, the foam cylinder  38  may be pressed together by hand, whilst simultaneously a push movement is carried out in the direction to the sheath  2 . With this, the elongate body may be pushed somewhat into the sheath  2 . 
     On retracting, the radial pressure on the foam cylinder  38  is reduced, so that the opening  35 ′ elastically enlarges again in the radial direction and the elongate body is released. Thus, the axial force introduction unit may then be retracted proximally with respect to the elongate body. 
       FIG. 17  shows a cross section through the foam cylinder  38  with the opening  35 ′. 
     A further variant of an axial force introduction unit is represented in  FIG. 18 , with a solid push cylinder  41  which comprises a guide tube  28 ″ which may be guided on the guide cylinder  29  as is represented in  FIG. 14 . 
     In the case which is represented in  FIG. 18 , the cylinder  41  itself is manufactured from an incompressible material, but is divided in the longitudinal direction into two halves, so that two segment bodies of the cylinder  41  result, as is represented in  FIGS. 19 and 20  in different variants. Firstly, according to  FIG. 19 , the cylinder  41  may be completely cut through and consists of two halves  44 ,  45  connected only by springs  42 ,  43 . These in the relaxed condition of the springs  42 ,  43  have a distance which is dimensioned such that the elongate body  10  is located in the central recess  35 ″ with play. If the halves  44 ,  45  are pressed together against the force of the springs  42 ,  43 , the elongate body may be clamped in the opening  35 ″. The elongate body may then be advanced in the clamped condition. The two halves  44 ,  45  of the cylinder  41  may for example be pressed together by hand on manipulating the push device, and may be let go when retracting the cylinder  41 . 
       FIG. 20  shows a similar design form, wherein the cylinder  41  is not completely separated into two halves, but a film joint  46  remains on one side of the cylinder  41 , and this joint permits the two halves  44 ′,  45 ′ to be folded open. One may also provide a separate hinge instead of the film joint  26 . The manner of functioning on clamping the elongate body corresponds to that represented by way of  FIG. 19 . 
       FIG. 21  shows a push device which is different from the devices which are represented in the previous figures. Here, a flange  46  of a guide body  47  is fastened on a sheath  2 , and to be more specific, on its flange  6 . The guide body  47  comprises a guide rail for the elongate body  10  which for example may be given by a semi-cylindrical or part-cylindrical recess, in which the elongate body  10  may lie. 
       FIG. 22  in a cross section shows the guide body  47  with the part-cylindrical recess  48  in which the elongate body  10  lies. 
     In  FIG. 21 , a drive body  49  is represented above the guide body  47 , and this drive body forms the axial force introduction unit. This drive body  49  for example likewise comprise a part cylindrical recess which receives the elongate body  10  at least partly. The drive body  49  may be displaced proximally or distally in the axial direction, represented by the double arrow  50 . A particular feature of the guide body  47  and of the drive body  49  may for example be realized by way of the friction between the drive body  49  and the elongate body  10  on account of the material selection with higher coefficients of static friction, being significantly larger than the friction between the elongate body  10  and the guide body  47 . For example, the guide body  47  may consist of a particularly smooth material with a low coefficient of friction, for example PTFE or may be coated with such a material. 
     The drive body  49  for its part may consist of a material which has a greater coefficient of friction compared to the elongate body  10 , such as of an elastomer, particularly rubber or silicone rubber. By way of this, if the drive body  49  is pressed radially against the elongate body  10 , the elongate body  10  may be moved axially in the fixed guide rail by way of displacement of the drive body in the axial direction. 
     Usefully, on introducing the elongate body  10  into the sheath  2 , this is simultaneously pressed onto the drive body and moves this distally in the direction of the sheath  2 . On retracting the drive body away from the sheath  2 , the pressing force on the elongate body is reduced, so 
     that this is not caught and remains in the sheath  2 . In this manner, the elongate body may be moved along in the sheath  2  in steps. 
     According to  FIG. 23 , a pistol-like handgrip may also be provided on the guide body  47  and this hand grip comprises a lever  51  which is movable against a spring  52 . The lever  51  is pivotably mounted and comprises a plunger  53  which presses against a clamping disk  54 , clamps this with respect to the drive body  49  and thereupon effects a push movement of the drive body  49 . The clamping disk is spring-loaded opposite to the direction of the arrow  55 . 
     The device shown in the  FIGS. 9-23  may on the one hand be used for a second sheath, in order to press this as an elongate body against a first sheath and to permit the pushing-through of a pump head with a minimized risk of a buckling of the pump catheter. On the other hand, this device may also be connected proximally to a holding device of a second sheath which is shown in the  FIGS. 3-8 , in order to permit the inserting of a catheter (as the case maybe with a pump head) into the second sheath without a buckling. Thus, two push devices may be combined with one another in this manner.