Abstract:
A device for administering a cannula ( 14 ), having a basic element ( 10 ),the cannula ( 14 ), a tip ( 16 ) of which protrudes beyond the basic element ( 10 ) in a ready to use position of the device, a traction element ( 12 ), which is movable with respect to the basic element ( 10 ), and a releasable pretensioning device ( 36, 38, 40 ) for pretensioning the traction element ( 12 ) with respect to the basic element ( 10 ) in the ready to use position of the device, wherein the traction element ( 12 ) interacts with the cannula ( 14 ) so that, when the pretensioning device ( 36, 38, 40 ) of the traction element ( 12 ) is released, the tip ( 16 ) of the cannula ( 14 ) retracts into the basic element ( 10 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is the national stage entry of PCT/EP2008/006211, filed Jul. 28, 2008, which claims priority to German Patent Application No. 20 2007 011 154.1, filed Aug. 9, 2007. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a device for administering a cannula. 
     In particular, the invention relates to a device for the percutaneous introduction of a cannula into an implanted port of a port catheter system. Such a port typically has a closing element, for example, of silicone, which is pierced by the cannula. The port catheter system may, for example, be a venous catheter for chemotherapy. 
     A device for administering a cannula is known, for which, after the port of a catheter is punctured with the cannula and after a drug, for example, has been injected through the cannula, the device for pulling out the cannula is restrained at the patient in order to retract the cannula into the device. The cannula is retracted into the device in order to hide the tip of the cannula and, by so doing, to decrease the risk of injury. The counter pressure, exerted on the device during this procedure, may cause the tip of the cannula to become slightly curved before it is pulled out, so that the closing element of the port is damaged by the deformed tip during the retraction. For example, small parts of the closing element could be cut out so that, after being punctured repeatedly, the closing element may start to leak. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to create a device of the type mentioned above, which, after an implanted port is punctured, makes it possible to withdraw the cannula easily and with the least possible destruction. 
     This objective is accomplished by a device for administering a cannula, which has
         a basic element, for example, for supporting the device on the skin of a patient,   a cannula, the tip of which, in the ready to use position of the device, protrudes beyond the basic element,   traction element, which is movable with respect to the basic element, and a separable prestressing device for prestressing the traction element with respect to the basic element in the ready to use position of the device,
 
wherein the traction element interacts with the cannula in such a manner that, when the prestressing device is released, the traction element retracts the tip of the cannula back into the basic element.
       

     In the ready to use position, the traction element preferably is disposed at the basic element and, in particular, is held at the latter. Preferably, the traction element is disposed at a lid of the device. 
     Since, according to the invention, the prestressing device retracts the cannula by way of the traction element, the basic element can, in the meantime, be held fast in the unchanged position without the need for exerting a counter pressure in the direction of the puncture site. By these means, it is ensured that the tip of the cannula is not curved or bent. Accordingly, the cannula is taken care of and damage to the port is avoided. In addition, the inventive device may be operated with one hand, since a second hand is not required for taking hold of the cannula. This simplifies the progress of the work appreciably. 
     The device is used in that, in the ready to use position, the cannula, protruding with its tip over the basic element, is introduced through the skin of the patient into the port implanted thereunder. In so doing, the basic element of the device comes to rest against the skin of the patient and can then serve to support the device on the skin of the patient. After, for example, a medicament has been injected via the cannula, the basic element is held firmly, for example, by taking hold of it at the side, for pulling out the cannula, and the pretensioning device is separated. By these means, the tip of the cannula is retracted automatically into the basic element. 
     Advantageous developments of the invention arise out of the dependent claims. 
     Preferably, the device is designed for a one-handed manipulation for holding the basic element in place and for releasing the pretensioning device, while the basic element is in contact with the skin of a patient. This means that the needle can be pulled out while, at the same time, the basic element is held fast, and that only one hand is required for this. In contrast to this, a manipulation with two hands is always required for administering a cannula with conventional devices, since the cannula is pulled out with one hand in that, for example, a handle element is taken hold of and pulled away from a basic element in a direction parallel to the main axis of the cannula, while the device is restrained at the patient with a second hand. 
     Preferably, the device has at least one actuating element for releasing the prestressing device, the actuating device being actuated by moving, especially by pressing the actuating element in a direction at right angles to the cannula. Accordingly, for releasing the prestressing device, pressure is not exerted in the direction of the port. Preferably, especially the actuating element is actuated by pressing the actuating element in the direction of the central axis of the cannula. In particular, the aforementioned pressing is pressing with one hand, that is, with one or more fingers. 
     Preferably, the basic element can be held by taking hold of the actuating element and of an opposite side of the actuating element, especially with only one hand. 
     Preferably, the pretensioning device can be released by pressing the actuating element by taking hold of the basic element at the side. Preferably, the actuating element can be pressed in a direction at right angles to the cannula, in order to release the pretensioning device. In other words, the pretensioning device can be released in that the actuating element can be pressed in a direction at right angles to the cannula by laterally taking hold of the basic element at least in one area of the actuating element and exerting pressure on the actuating element. 
     Together with the cannula, inserted into the skin of the patient, the device is thus taken hold of at the side with one hand, that is, at right angles to the cannula on two opposite sides, for example, with two fingers, such as the forefinger and the thumb, and the pretensioning device is released by a compression. 
     Preferably, a locking element is disposed at the actuating element and a counter piece to the locking element, which is held in the ready to use position at the locking element, is disposed at the traction element. The pretensioning device is released in that the locking element releases the counter piece. For example, the locking element, disposed at the actuating element, is released from its counter piece by pressing and shifting the actuating element in the direction of the central axis of the cannula. It is particularly preferred if the actuating element forms the locking element or several locking elements for corresponding counter pieces of the traction element. Since there is only a movement at right angles to the direction of the cannula and accordingly at right angles to the direction of force of the pretensioning device, the pretensioning device can be released particularly easily, without the need for exerting a force in the direction of the port. 
     Preferably, the actuating element is plate-like and held at the basic element. In the ready to use position, the traction element is locked at the actuating element; the locking can be released by moving the actuating element in a direction at right angles to the cannula. As a result, the construction of the device is particularly simple and flat. 
     Preferably, the actuating element is held movably at the basic element and, in particular, displaceably in a direction at right angles to the cannula. In the ready to use position, at least one locking element of the traction element engages from behind a locking element of the actuation element in the form of a region of the actuating element. This region is shaped, so that it can be disengaged from the locking element of the traction element by moving the actuating element in a direction at right angles to the cannula. Since the region of the actuating element releases the locking element of the traction element in this manner, the pretensioning device is releaseable. 
     Preferably, a region, engaged from the rear in the ready to use position by a locking element of the traction element, is located at an edge of the actuating element, particularly at a lateral edge, which edge runs at right angles to a displacement direction of the actuating element and/or at which edge the actuating element is held displaceably at the basic element. 
     The arrangement of several such locking elements of the traction element in the ready to use position around the cannula, for example, four locking elements at opposite edges of an essentially rectangular actuating element, is particularly preferred. Preferably, a recess, through which the respective locking element can pass for its release, is provided at the respective region. 
     Since only a movement of the actuating element at right angles to the direction of the cannula and consequently at right angles to the direction of force of the pretensioning device is required for releasing the locking elements of the actuating element from the counter pieces of the traction element, the pretensioning device can be released particularly easily. Moreover, it is sufficient to provide a single, displaceable actuating element, which can be shifted, for example, directly by pressing against the outer edge thereof, which is disposed at the periphery of the device. 
     In a further embodiment, the at least one actuating element is disposed at a frame, which extends in the vicinity of the outer edge of the basic element and is connected at its ends with the basic element. In particular, the frame extends semi circularly around the basic element. By these means, the frame with the actuating element can be taken hold of particularly well. Furthermore, because it is connected with the basic element on both sides, the frame ensures that the actuating element is guided to some extent. 
     Optionally, two actuating elements for releasing the pretensioning device are disposed opposite to one another at the basic element. As a result, the actuating elements are particularly suitable for holding the basic element with one hand and, while simultaneously compressing the two actuating elements, a lateral displacement of the cannula or the exertion of a transverse force on the cannula is effectively prevented. The two frames of the fastening element form, for example, a ring, which encompasses the basic element. 
     Preferably the device has at least one closing element for hiding the tip of the cannula, when the latter is retracted into the basic element. 
     Optionally, the closing element can be moved by the force of a spring into a position, in which the tip is hidden. For example, the closing element may be disposed at a spring element and be pretensioned in the ready to use position and actuated by actuating the actuating element, in order to assume a hiding position, in which the tip is retracted into the basic element. For example, the closing element may be pretensioned laterally against the cannula in the ready to use position. When the tip of the cannula is retracted past the closing element into the basic element, the closing element is thus triggered automatically. The closing element may, for example, be a plate-like element, which is constructed in one piece with a laterally protruding leaf spring. By loosening the pretensioning, the plate-like element can be moved laterally and transversely to the cannula. 
     It is particularly preferred if the actuating element forms the closing element. Preferably, the actuating element has an opening for the cannula in the ready to use position. Since the actuating element forms the closing element directly, a construction results, which can be actuated a particularly easily and reliably. 
     Preferably, the closing element is disposed in the vicinity of an underside of the basic element, that is, in the vicinity of the side directed to the tip of the cannula. This is the side facing the skin of the patient. For example, the device has two closing elements on opposite sides, which can be shifted into a position, in which the front ends thereof are in front of the tip. Due to the at least one closing element, damage to the tip of the cannula after use of the device is precluded. Preferably, the closing element is held so that it can be shifted at the basic element. 
     Preferably, the closing element is held at the basic element so that, if the actuating element is pressed in the direction at right angles to the cannula, the closing element can be moved in front of the tip of the cannula, which has been retracted into the basic element. This is accomplished, for example, in that the actuating element has a finger or is connected with a finger or controls a finger, which shifts the closing element. For example, the finger may be disposed at the above mentioned locking element or connected therewith. By these means, the pretensioning device can be released with a single movement of the actuating element and, after the cannula has been retracted immediately, the closing element can be moved in front of the tip. 
     In turn, it is particularly preferred, if the actuating element forms the closing element. 
     Preferably, the device has a locking arrangement for locking the closing element in the position, in which the tip is hidden. The locking arrangement preferably consists of detent elements, which are provided at the actuation element and at the basic element. For example, the displaceable actuating element, held at the basic element, may have detent lugs, which protrude transversely to the displacement direction and engage the position in the detent notches of the basic element, hiding the tip. Furthermore, the locking arrangement may, for example, consist of a second locking element, which is connected with the actuating element or is disposed at this element and of a receptacle at the basic element assigned to the locking element. The locking element may be disposed, for example, at the aforementioned finger. The locking arrangement ensures that the tip of the cannula is not exposed once again. 
     The locking with the detent element prevents the closing element being pushed back once again. 
     Preferably, the actuating element is plate-like and is held displaceably at the basic element, forms the above-mentioned closing element and, in the ready to use position, engages the above-mentioned locking elements of the traction element. The pretensioning element can be released by shifting the actuating element and, by shifting the actuating element further, a closing region of the actuating element can be moved in front of the tip of the cannula, which has been retracted into the basic element. Since first of all the pretensioning device is released by pressing on the actuating element, so that the cannula can be retracted and the tip of the cannula is then hidden and optionally the actuating element is locked in the position hiding the tip, the pretensioning device is released and the retracted cannula is secured thereby by a single, linear movement of the actuating element. A particularly functionally secure construction of the device and very reliable handling accordingly thus result. 
     Optionally, the device has at least one latch, which protrudes into the basic element transversely to the cannula and can be advanced by actuating the actuating element. The latch has the locking element, forms a finger for moving the closing element in front of the tip of the cannula, which is retracted into the basic element, and has a component of the locking arrangement for locking the closing element. With this component, the latch can be engaged at the basic element at an assigned receptacle. Preferably, the latch is connected with the actuating element or is a part of the latter. The locking arrangement accordingly consists of its component, which forms a part of the latch, and of the assigned receptacle at the basic element. Preferably, the latch protrudes in the direction of the central axis of the cannula into the basic element. Since the latch is moved in this direction by pressing on the actuating element, first of all the pretensioning device is released by a single, linear movement, so that the cannula is retracted, and the closing element is then pushed in front of the tip of the cannula, the latch being engaged at the basic element. As a result, the closing element cannot be pushed back again. Once again, the handling of the device is very simple. This construction of the device is also particularly secure functionally. 
     Once again, by pressing on the actuating element with a single, linear movement, the pretensioning device is released, the closing element is shifted in front of the tip of the cannula and the latch is engaged at the basic element. 
     Preferably, the cannula is a port-puncturing needle for a port catheter system, in particular, a Huber needle. Preferably, the cannula is provided with a connection for a tube. 
     Preferably, in the vicinity of the tip, the cannula is provided with a section, the cross-section of which is enlarged relative to a cannula shaft. This is the case, for example, for a port needle, which has a Huber ground surface and a cannula shaft with a diameter of 1.1 mm and, at a bend in the vicinity of the tip, a maximum diameter of 1.4 mm. Preferably, at a site remote from the underside of the basic element, the latter has a passage opening for the shaft of the cannula and this passage opening has a cross-section, through which the section of the cannula with the enlarged cross-section cannot pass. In the example named, the passage opening is cylindrical with a diameter of 1.2 mm. The passage opening and the closing element or actuating element are disposed so that, when the tip of the cannula is retracted, the cannula section with the enlarged cross-section remains hanging at the passage opening, so that the tip of the cannula is in the interior of the basic element between the passage opening and the closing element. With that, secure protection against injury is achieved. 
     Preferably, the pretensioning device has a compression spring, which is disposed between the basic element and the traction element or a lid, at which the traction element is disposed. The compression spring is, for example, a helical spring, preferably a spirally extending, for example, conical leaf spring, the main loading direction of the compression spring extending in the direction of the cannula. Preferably, the compression spring is disposed ring-shaped or spiral-shaped around the middle axis of the cannula. Preferably, in the case of the pretensioned pretensioning device, the transverse extension of the compression spring is larger than the axial extension and, in particular, several times as large as the axial extension. This results in a flat construction of the device. 
     Preferably, a bottom element, particularly a bottom plate of the basic element, is disposed in front of an underside of the actuating element, that is, in front of that side, at which the cannula protrudes in the ready to use position. Preferably, this forms a support for supporting the device on the skin of the patient. The movement of the actuating element is facilitated by such a bottom element while the device is lying in contact with the skin of the patient, since the actuating element does not have to be shifted directly on the skin. 
     Preferably, in the longitudinal direction of the cannula, the actuating element is at a distance from the supporting surface of the basic element for supporting the device on the skin of a patient. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, examples of the invention are explained in greater detail by means of the drawing, in which 
         FIG. 1  shows a section through an inventive device with a basic element and a traction element in the form of a lid, at which the cannula is held, 
         FIG. 2  shows a view of the device from below with the bottom plate removed, the line I-I corresponding to the section shown in  FIG. 1 , 
         FIG. 3  shows an exploded representation of the device corresponding to  FIG. 1 , 
         FIG. 4  shows a view of the device, together with the bottom plate, from below, 
         FIG. 5  shows a view of the device from above, 
         FIG. 6  shows a section through a device of a second embodiment with a basic element and a traction element in the form of a lid, at which a cannula is held, 
         FIG. 7  shows a view of the basic element of the device of  FIG. 6  from below, the line VI-VI corresponding to the section shown in  FIG. 6  and 
         FIG. 8  shows a side view of the traction element and the lid of  FIG. 6  with the cannula. 
     
    
    
     DETAILED DESCRIPTION 
     The device, shown in  FIG. 1 , has a housing, which consists of a basic element  10  and a traction element  12 , which, at the same time, forms a lid of the housing. The basic element  10  and the traction element  12  have essentially a cylindrical external cross section. Along their common central axis, a cannula  14  is disposed, the tip  16  of which protrudes through an opening  15  in the basic element  10  and, in the ready to use position shown in  FIG. 1 , protrudes so far beyond the flat underside of the basic element  10 , that a port of a port catheter system, implanted subcutaneously, can be reached. The protruding length of the cannula is dimensioned, for example, so that, when the cannula  14  is introduced into the port, the basic element  10  can be supported with its underside on the skin of the patient. The cannula  14  is constructed, for example, as a Huber needle and has a shaft with a diameter of 1.1 mm and, above the cannula opening at a bend, a section  17  with a maximum diameter of 1.4 mm. 
     The basic element  10  forms a flat pot  18  with a ring-shaped side wall  19 . In the center of the pot  18 , an internal, cylindrical wall  24 , which at its upper end has a passage opening for the shaft of the cannula in the form of a constriction  25  with a diameter of, for example, 1.2 mm, is formed above the opening  15 . 
     The traction element  12  forms a lid for the pot  18  and, in the center thereof, carries a holding device  26  for the cannula  14  and a tube  28 , which is connected liquid-tight therewith. 
     In a depression at the underside of the pot  18 , a plate-shaped element  30  is mounted displaceably and is received at its underside by a bottom plate  32  of the basic element  10 . In  FIG. 1 , the element  30  can be shifted back and forth in the viewing direction. 
       FIG. 2  shows that the actuating element forms locking elements in the form of regions  36 . Counter pieces  38  thereto are formed at the underside of the traction element  12  in the form of locking elements, which protrude downward from either side of the element  30  and are essentially L-shaped with a projection  39  extending below a region of the element  30 . This can be seen especially in  FIGS. 2  and  3 . For a better illustration,  FIG. 3  shows the sectional view of  FIG. 1  in an exploded representation. 
     In a ready to use position of the device, element  30  is taken hold of from the rear at the regions  36  of the counter pieces  38  with the projections  39 , so that the traction element  12  is locked by way of the projections  39  at the element  30  and, accordingly, at the basic element  10 . In this position, the traction element  12  is pretensioned against the basic element  10 , in that a compression spring  40  ( FIG. 1 ) is disposed pretensioned between the bottom of the pot  18  and the lid of the traction element  12 .  FIG. 3  also shows the compression spring  40  in the pretensioned state. 
     In  FIG. 2 , it can be seen that the element  30  has the regions  36 , as well as lateral recesses  41  at the edge. At its front edge (in  FIG. 2  at the top), the element  30  has a gripping surface  42  which is freely open and accessible by a first finger of a hand of a person. The pretensioning device, formed by the locking elements  38 , the regions  36  of the element  30  engaging the pretensioning device and the compression spring  40 , is released by taking hold of the gripping surface  42  and pressing the element  30  inward in the direction of the central axis of the cannula  14 , in that element  30  is shifted, so that the projections  39  reach the recesses  41  and are released by the regions  36 . Appropriate recesses  43  are provided in the bottom of the pot  18  and indicated by broken lines in  FIG. 1 . 
     Because of the release of the locking elements  38 , the traction element  12  is lifted from the basic element  10  by the pressure of the compression spring  40 . At the same time, the projections  39  emerge upward out of the bottom of the pot  18 . The gripping surface  42  and the element  30  accordingly form an actuating element for releasing the pretensioning device. 
     When the traction element  12  is lifted from the basic element  10 , it takes along the cannula  14 . By these means, the tip  16  is retracted behind the opening  15 . Element  30  has a sufficiently large opening  46 , to permit element  30  to be shifted in spite of the cannula  14  passing through. The cannula, with its section  17  of larger cross section, gets stuck at the constriction  25  of the wall  24 , so that the tip  16  is hidden in the interior of the pot  18 , surrounded by the wall  24  and, in this way, protected against contact. 
     When element  30  is pushed further, it finally closes the opening  15  in that a closed region of the element  30  is now located in front of the tip  16  of the cannula  14 , which has been retracted into the basic element  10 . Small detent lugs  48 , which, when element  30  is pushed in completely, engage detent accommodations  49  in the bottom of the pot  18 , are formed laterally at the element  30 . The detent lugs  48  and the detent accommodations  49  together form a locking device for the element  30 , which prevents element  30  being pushed back. By these means, the opening  15  is closed reliably, so that the tip  16  of the cannula  14  cannot emerge once again. Accordingly, the element  30  hides the tip  16 . 
     By taking hold of the gripping surface  42  and, optionally, the opposite side of the pot  18  of the device described and pressing the element  30  inward, initially the locking element  38  of the lid of the traction element  12  is released through the recesses  41  and, in this way, the pretensioning device is released and the cannula  14  is retracted into the basic element  10 . As the element  30  is pressed in further, it ends up in front of the retracted tip  16  of the cannula  14 , hiding the latter, and is locked in this position by the locking device  48 ,  49 . 
       FIG. 4  shows a view corresponding to  FIG. 2 , however, with the bottom plate  32  set down. The latter is aligned over four projections  50  at the underside of the pot  18  and corresponding recesses in the bottom plate  32 . The bottom plate  32  also has recesses for the locking elements  38  with the projections  39 , so that a particularly flat construction is achieved. 
       FIG. 5  shows a view of the device from above. A safety element  52  is inserted between an upwardly protruding edge of the element  30 , at which the gripping surface  42  is formed, and the outer wall of the pot  18 . The safety element  52  may be jammed, for example, between an upwardly protruding edge of the element  30  and the wall of the pot  18 . Its function is to prevent element  30  being pushed in accidentally. The safety element  52  can be removed by taking hold of a handle  54 , when the device is to be actuated. 
       FIGS. 6 to 8  show a second embodiment of the device, which differs from that shown in  FIGS. 1 to 5  with respect to the number and type of actuating elements as well as the construction of the locking device for the pretensioning device. Elements, which correspond to one another, have been given the same reference numbers. 
     The side wall  19  of the pot  18 , indicated by a broken line in  FIGS. 6 and 7 , and the pot  18  are surrounded at a distance by an annular element, which is connected with the pot  18  at two opposite sides by bridges  60  and, in this way, is divided into two frames  62  in the form of half rings. 
       FIG. 7  shows that, at each frame  62 , a latch  70 , directed inwardly to the pot  18 , is integrally molded in the middle between the bridges  60 . At its front end, the latch  70  forms a harpoon-like spread  48 ′, which interacts with a suitably shaped detent receptacle  49 ′. When the latch  70  is pushed into the detent receptacle  49 ′, the spread  48 ′ engages the detent receptacle  49 ′, so that the latch  70  is held firmly. 
     Locking elements  36 ′ are formed on the latches  70  in the shape of lateral projections behind the spread  48 ′. These locking elements  36 ′ are disposed at the upper side of the latch  70 . Corresponding locking elements, which form counter pieces  38 ′ of the locking elements  36 ′ and, in the ready to use position, are held at the locking elements  36 ′, so that the traction element  12  is locked at the latches  70  and, with that, at the basic element  10 , are disposed at the edge of the lid of the traction element  12 . In this position, the traction element  12  is pretensioned in turn against the basic element  10 , in that the compression spring  40  ( FIG. 6 ) is disposed pretensioned between the bottom of the pot  18  and the lid of the traction element  12 . 
     At the outside in each case opposite the latch  70 , the frames  62  have a gripping surface  42 . The pretensioning device, formed by the locking elements  36 ′, the counter pieces  38 ′ thereof and the compression spring  40 , is released by taking hold of the opposite gripping surfaces  42  and pressing the latches  70  inward in the direction of the central axis of the cannula  14 , in that the locking elements  36 ′ are moved radially inward and, at the same time, release the counter pieces  38 ′, so that the traction element  12  is raised up from the basic element  10  by the pressure of the compression spring  40 . The gripping surfaces  42  and the latch  70  accordingly form the actuating element for releasing the pretensioning device. In much the same way as with the first embodiment, the cannula  14  is taken along when the traction element  12  is raised from the basic element  10  and the tip, surrounded by the wall  24 , is hidden in the interior of the pot  18 . 
     Two mutually opposite closing elements, in the form of closing plates  84 , are disposed displaceably in the bottom of the pot  18 . The closing plates  84  are on an imaginary line, connecting the two latches  70  and passing through the cannula  14 , and can be shifted parallel to this line. The closing plates  84  extend to the outside in each case as far as just before the latch  70 , so that, when the latch  70  is pushed into the detent receptacle  49 ′, they are advanced in the direction of the center axis of the cannula  14 . When the latch  70  with the spread  48 ′ is locked at the detent receptacle  49 ′, the respective front end of the closing plate  84  is in front of the tip  16  of the cannula  14 , which has been retracted into the basic element  10 . Accordingly, the latch  70  forms a finger for moving the closing plate  84  inward from the tip  16  of the retracted cannula  14 . The spread  48 ′ and the detent receptacle  49 ′ together form a locking device for the closing plate  84 , which prevents the closing plate  84  being pushed back. By these means, the opening  15  is closed reliably, so that the tip  16  of the cannula  14  cannot emerge once again. Accordingly, the closing plates  84  hide the tip  16 . 
     For the second embodiment of the device, by taking hold of the gripping surfaces  42  which are freely open and accessible by the fingers of a hand of a person and pressing the frames  62  together, it is achieved, first of all, that the locking elements  36 ′ release the lid of the traction element  12  by pressing the latches  70  inward and thus release the pretensioning device, and that the cannula  14  is retracted into the basic element  10 , whereupon, as the latches  70  are pressed inward further, the closing plates  84  move in front of the tip  16  of the cannula  14 , hiding the latter, and are locked in this position by the locking device  48 ′,  49 ′.