Patent Publication Number: US-2011060312-A1

Title: Connection system for connecting a fluid line to a fluid reservoir

Description:
TECHNICAL FIELD 
     The disclosure relates to a connection system for connecting a fluid line to a fluid reservoir located within a device, and in particular within a medical device such as, e.g., an insulin pump. 
     BACKGROUND 
     It is known to connect a fluid line to a fluid reservoir by way of adapted connectors. The reservoir may be an ampoule provided with a connector to which a so-called Luer connector fixed to one end of the fluid line can be attached. Such connection systems are, for example, used in medical pumping devices, e.g., portable insulin pumps, wherein the ampoule contains insulin is placed within the pump. The insulin is dosed by the pump and fed via the fluid line to the patient in a known manner. An improved connection system is still desired. 
     SUMMARY 
     In one embodiment, a connection system for connecting a fluid line to a fluid reservoir located within a device by way of a cannula is disclosed. The connection system may include a cannula holder holding the cannula and comprising a movable cannula cover and a lock for the cover, which prevents the movement of the cannula cover in a first state covering the cannula. A receiving element which receives the cannula holder can be provided, wherein the receiving element can be fixed to the device or formed a part thereof. The receiving element may comprise a release which interacts with the lock, and wherein the release and the lock are arranged to release the cannula cover by the release interacting with the lock, so that the cannula cover is movable by the inserting force to expose the cannula when the cannula holder is inserted into the receiving element, and so that the cannula cover is in a second state exposing the cannula when the cannula holder is inserted within the receiving element. 
     In another embodiment, a medical pumping device is disclosed having a receiving element of a connection system according to any one of the embodiments described herein. 
     In still another embodiment, a method of connecting a fluid line to a fluid reservoir located within a device by way of a cannula is disclosed. The method comprises utilizing a connecting system according to any one of the embodiments described herein. 
     These and other features of the various embodiments of the invention will become apparent from the following detailed description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the figures, like reference numerals depict the same or functionally equivalent elements, wherein: 
         FIG. 1  shows a first embodiment of a connecting system wherein a receiving element is an adapter to be fixed to a device; 
         FIG. 2  shows a sectional view of the cannula holder of  FIG. 1  with a cannula cover in a first state covering a cannula; 
         FIG. 3  shows the cannula holder of  FIG. 2  with the cannula cover in the second state exposing the cannula; 
         FIG. 4  shows a sectional view of the cannula holder of  FIGS. 1 to 3  ready to be inserted in the receiving element of the system; 
         FIG. 5  shows a sectional view of the cannula holder of  FIG. 4  inserted into and fixed to the receiving element and with a pierced ampoule; 
         FIG. 6  shows a sectional view similar to  FIG. 4 , but rotated 90 degrees about the longitudinal axis of the cannula so that a lock and a release can be seen; 
         FIG. 7  shows the sectional view of  FIG. 6  with the cannula holder inserted within the receiving element; 
         FIG. 8  shows a perspective view of a cannula cover with parts of a lock; 
         FIG. 9  shows a perspective view of a part of a cannula holder with other parts of a lock; 
         FIG. 10  shows a sectional view of a cannula holder with a cannula cover and a part of a receiving element with a release; 
         FIG. 11  shows a sectional view of a part of a cannula holder inserted into a receiving element; 
         FIG. 12  shows a sectional view of a device with a connection system according to a second embodiment with a cannula holder and a receiving element, wherein the receiving element forms part of the device itself; 
         FIG. 13  shows the cannula holder and the device of  FIG. 12  in separated state before loading of the ampoule into the device; 
         FIG. 14  shows a first step of the opening of the device of  FIG. 13 ; 
         FIG. 15  shows a second step of the opening of the device of  FIG. 14 ; 
         FIG. 16  shows the insertion of an ampoule into the device of  FIG. 15 ; 
         FIG. 17  and  FIG. 18  show the closing of the device of  FIG. 16 ; 
         FIG. 19  shows a cannula holder in perspective view in exploded and assembled form; 
         FIG. 20  shows an exploded view for explaining a blocking element of the connection system according to the second embodiment; 
         FIG. 21  shows the elements of  FIG. 20  in assembled form; 
         FIG. 22  shows an unblocking of a cannula holder; 
         FIG. 23  shows blocking and unblocking elements of a third embodiment in exploded view; 
         FIG. 24  shows the blocking and unblocking elements of  FIG. 23  in a sectional view; 
         FIG. 25  shows in exploded view a connection system according to another embodiment with a form which locks rotational movement of a cannula cover; and 
         FIG. 26  shows the embodiment of  FIG. 25  in sectional view before inserting the cannula holder into a receiving element. 
     
    
    
     DETAILED DESCRIPTION 
     In one embodiment, a connection system for connecting a fluid line to a fluid reservoir located within a device by way of a cannula is disclosed. The system may comprise a cannula holder holding the cannula, a movable cannula cover, and a lock for the cover which prevents movement of the cannula cover in a first state which covers the cannula. The system may also comprise a receiving element for receiving the cannula holder. The receiving element may be either adapted for fixation to the device or form part of the device. The receiving element may comprise a release adapted for interaction with the lock. The release and the lock may be arranged to release the cannula cover by the release interacting with the lock, so that the cannula cover is movable by the inserting force to expose the cannula when the cannula holder is inserted into the receiving element, and so that the cannula cover is in a second state exposing the cannula when the cannula holder is inserted within the receiving element. By this connection system the cannula is protected automatically and gives, on the one hand, secure operation to the operator thereby preventing injury risks by the cannula, and prevents, on the other hand, staining of the cannula. The connection system can be easily adapted for one-hand operation. 
     In another embodiment of the connection system, while the cannula holder is being removed from the receiving element, the cannula cover is moved by an energy storage device in a direction opposite to the movement of the cannula cover during insertion of the cannula holder into the receiving element. This helps considerably for a one-hand operation if the energy storage element is selected such that it actively pushes the cannula holder out of the receiving element when the connection is released again. If the connection accidentally becomes loose, it will disconnect by itself if the energy storage element is selected for providing enough force, so that a connection that has become loose-fitting by accident is released. In one embodiment, the cannula cover is held slidably within the cannula holder for a sliding translation movement in longitudinal direction of the cannula. This embodiment allows for a very compact connection as the cannula cover does not have to have a size which takes up the collar of the reservoir. In one embodiment, the energy storage device may be a coil spring. 
     In an alternative embodiment to the energy-storing element, the cannula cover is held within the cannula holder by a guide imparting a rotational screw-in and screw-out movement to the cannula cover within the cannula holder during the insertion and the removing of the cannula holder from the receiving element. In one embodiment the lock comprises a catch on the cannula cover which is adapted to lock into a recess of the cannula holder, and the release comprises a rib within the receiving element which is adapted to release the catch from the recess. The catch may be a two-stepped catch comprising a first block-shaped step and a second step which is held by an elastically deformable tongue. In one embodiment, the connection system may comprise blocking elements for blocking of the cannula holder after full insertion into the device and unblocking elements for unblocking of the cannula holder and for releasing the cannula holder from the device. In another embodiment, an unblocking element is provided for one-handed operation of the release, which allows for easy operation of the connection system. The receiving element in one embodiment is part of a medical device, which obviates the need for a separate adapter. In such an embodiment, the medical device takes up the forces in connection with the pumping of the liquid, which allows a simpler construction of the connection. In one embodiment, the receiving element may be a part of an insulin pump. In still another embodiment, the cannula holder is essentially L-shaped, wherein the cannula is held essentially in a 90 degree angle to the line exiting the cannula holder. This embodiment allows a full integration of the connection system into the shape of the medical device and results in an advantageous exit of the fluid line. In another embodiment, the receiving element may be mounted to the device such that it can be swiveled about an axis for opening a chamber that is adapted to receive the liquid reservoir. This embodiment, as well, allows for a good adaptation of the connection system to a portable fluid pump. 
     Other embodiments of the invention further relate to a medical pumping device with a receiving element according to the invention. This medical pumping device may be a portable medication pump in one embodiment and in particular, an insulin pump in another embodiment. 
     With reference to  FIGS. 1 to 11 , a first illustrated embodiment of the invention is now described.  FIG. 1  shows an overview of this first illustrated embodiment of the connecting system  1 . There is provided a cannula holder  4  holding a cannula that cannot be seen in  FIG. 1  since this cannula is covered by cannula cover  7  which prevents an accidental touching of the cannula by the user of the system. Within cannula holder  4 , the cannula is in fluid connection with line  6  which shall be connected by the system to a reservoir  3  containing the fluid. This reservoir, in particular an ampoule, for example, containing insulin, is provided within a device  2  which is only indicated in this embodiment by a part of its housing. 
     This device is, for example, a medical device in one embodiment and in particular, an insulin pump in another embodiment for dosing insulin out of reservoir or ampoule  3 , respectively, to a patient via tube or line  6  that leads to another cannula at its other end (not shown) for insertion into the body of the patient. The system according to this embodiment comprises a receiving element  10  into which the cannula holder  4  is to be inserted in the form of an adapter, which is shaped so that it fits the device  2 , and preferably surrounds the upper part of the reservoir  3  in another embodiment. The cannula  5  ( FIG. 2 ) within the cannula holder  4  is inserted into the reservoir  3  when the cannula holder  4  is inserted into the adapter or receiving element  10  in this embodiment. A lock, generally shown as  11 , prevents the cannula cover  7  from being moved or released, respectively, unless upon insertion of the cannula holder  4  into the receiving element  10 . 
     Upon insertion, a release within the receiving element  10  interacts with the lock  11  so that the cannula cover  7  moves. In one particular embodiment, the cannula cover  7  slides backwards, away from the tip of the cannula  5 , to expose the cannula within the receiving element  10 , so that the reservoir  3  can be pierced by the cannula  5  to establish the fluid connection between the reservoir  3  and line  6 . In case of an ampoule, a septum closing the ampoule is pierced by the cannula. One or more blocking elements, generally depicted as  20  in  FIG. 1 , lock the fully inserted cannula holder  4  within the adapter or receiving element  10 . An unblocking element, part of which is generally shown as  40  in  FIG. 1 , serves for releasing the cannula holder  4  from receiving element  10 . Upon releasing the cannula holder, the cannula cover  7  is again brought in position as shown in  FIG. 1  to cover the cannula so that no contact of the person using the system with the cannula is possible, as will be explained in greater detail below. By this arrangement, the person is protected against injury by the cannula on the one hand and on the other hand, the cannula is protected against contamination. 
     The cannula holder  4  of this embodiment is generally shown as having a cylindrical outer shape and consequently the cannula cover  7  and the inner shape of the receiving element  10  receiving the holder is shown cylindrically as well. Of course, other shapes can be selected as well. The cannula holder  4  and the receiving element  10  of the system  1  will usually be made of plastic material. In some embodiments, the cannula holder  4  and the receiving element  10  are preferably one-piece elements as shown in the drawings, but may of course as well be multi-piece elements in other embodiments. 
       FIGS. 2 and 3  show a sectional view of the cannula holder  4  of the first embodiment of the connection system  1 . In these sectional views, the cannula  5  can be seen which is fixedly mounted within the cannula holder  4 , for example by being fully enclosed by plastic core  4 ′ of this cannula holder. Within holder  4 , the cannula  5  is in fluid connection with line  6 , so that fluid entering the cannula at its tip enters the line  6 . The cannula cover  7  fully covers cannula  5  in the first position or state, respectively, shown in  FIG. 2 . The cover  7  is locked in this position by the lock  11 , which is not visible in this section, until the release of the receiving element  10  ( FIG. 1 ) releases the lock, as will be explained below. When the lock  11  ( FIG. 1 ) is released, the cover  7  can be moved. 
     In one particular embodiment, the cannula cover  7  can slide backwards within space  9  in the cannula holder  4 , so that the cannula  5  becomes exposed as can be seen in  FIG. 3 , which shows the cover pushed fully backwards; because of the lock  11  ( FIG. 1 ), in this second position or state, respectively, shown here in  FIG. 3  for explanation purposes, the “free” cannula holder  4  can only be assumed when this holder is inserted within the receiving element  10  of the connection system  1 . The cannula  5  passes through the small opening  7 ′ of the cannula cover  7  during the backwards movement of the cannula cover. Preferably, an energy storage element  8  is provided which stores energy that becomes available by the insertion force applied by the user of the system  1  upon inserting the cannula holder  4  into the receiving element  10 . In some embodiments, the energy storage device  8  is a coil spring. 
     When the cannula holder  4  is again removed from the receiving element  10 , the stored energy is available to push the cannula cover  7  back into the first position covering the cannula  5  as shown in  FIGS. 1 and 2 , such that the lock  11  will again lock the cover  7  in this position. In some embodiments, the force exerted by the coil spring or energy storage device  8  on the cannula cover  7  may be selected to be relatively low by a corresponding spring size and spring rate. In this manner, this force of the energy storage device  8  serves essentially only to push the cannula cover  7  back over the cannula  5  when the cannula holder  4  has been unblocked by the user and is pulled out of the receiving element  10 . On the other hand, and preferably in one embodiment, the spring force is selected as being so great that the spring or energy storage device  8  acting on the cannula cover  7  significantly helps pushing the cannula holder  4  out of the receiving element  10  by the cannula  7  cover abutting on the receiving element  10  when the unblocking element  40  has been actuated by the user. 
       FIGS. 4 and 5  show the insertion of cannula holder  4  into the adapter or receiving element  10 , which is depicted in this embodiment within device  2  and in sectional view. In the sectional view of  FIG. 4 , a part of the release within receiving element  10  can be seen in the form of an elongated protruding member or rib  16  that interacts with the lock  11  for the cannula cover  7  of cannula holder  4  when the holder  4  is inserted into the receiving element  10 . In the section of  FIGS. 4 and 5  the lock  11  ( FIG. 1 ) cannot be seen, but will be shown and explained below with reference to  FIGS. 6 to 11 . On the one hand,  FIGS. 4 and 5  show the insertion of the cannula holder  4  and the piercing of the reservoir  3 , which in this embodiment is provided as an ampoule, by the cannula  5  in the inserted position ( FIG. 5 ). On the other hand these Figures show the blocking elements  20  for securing the inserted holder  4  within the receiving element  10  and the unblocking element  40  for the release of the holder  4  from the receiving element  10  by the user, which is usually done when an empty ampoule or reservoir  3  and/or the line  6  with the cannulae on both ends have to be replaced. In this embodiment, the blocking elements  20  are provided by interacting protrusions on the outside of the cannula holder  4  and on the inside of the receiving element  10 . In particular, wedge shaped protrusions  21  are provided on the outer circumference of the holder  4  and corresponding latches  22  are provided on the inner circumference of the receiving element  10 . The interaction of the protrusions  21  and latches  22  allows to insert the cannula holder  4  into the receiving element  10  and to block the holder in the fully inserted state. In the shown example, the latches  22  are bended by the wedge shaped protrusions  21  during the insertion and spring back (into their normal unbent positions shown in  FIGS. 4 and 5 ) in the fully inserted state of the cannula holder  4 . In the fully inserted state, the latches  22  contact the horizontal planes of the wedge shaped protrusions  21 , thus blocking the holder  4  in the fully inserted state. Several such interacting protrusions  21  and latches  22  may be arranged around the holder  4  and the receiving element  10 . The holder  4  and the receiving element  10  may be keyed, for example by a corresponding guide, so that the insertion can only be done in a position where the interacting protrusions align. This guiding is preferably provided by the interacting lock and release for the cannula cover  7 , but other matching keying elements can be provided to allow an insertion in a correct position only, so that interaction of the blocking elements occurs. 
       FIGS. 4 and 5  show as well the unblocking element  40 , which is in this example is provided as a collar that is slidably secured to the receiving element  10  and is provided with a ring or fingers  23  at the positions of the latches  22 , that bend the latches  22  in radial direction away from the wedge shaped protrusions or wedges  21  when the collar or unblocking element  40  is moved by finger pressure by the user in direction towards the cannula tip. In this manner, the latches  22  no longer block the wedges  21 , and thus the user can pull the cannula holder  4  out of the receiving element  10 . The pulling out is helped more or less, as outlined above, by the force of coil spring or energy storage device  8  that at the same time presses cannula cover  7 , abutting on ampoule  3 , over the cannula  5  during the pull-out movement of the cannula holder  4 . 
     With reference to  FIGS. 6 to 11 , the lock and the release for the cannula cover  7  can now be described in greater detail.  FIGS. 6 ,  7 ,  10  and  11  show sectional views wherein these means can be seen and  FIGS. 8 and 9  show perspective views of the cannula cover  7  and the main part of the cannula holder  4  for a better explanation. Further reference is made to  FIG. 4  wherein a part of the release is shown by rib  16  already mentioned. In one embodiment, the cannula cover  7  is provided with a two-step catch  25  having a narrower, wedge shaped step  26  and a wider, block-shaped step  27  and in other embodiments, with two such catches  25  that may be arranged opposed each other along the circumference of the cover  7 . In still other embodiments, two or more such catches  25  may be provided around the circumference of the holder  4 . In some of the embodiments, each catch  25  is formed at the end of an elastic tongue  28 , which allows the catch to be bent in inward direction of the cannula cover  7 , as can be seen in particular in  FIG. 11 , and to spring back into its rest position shown in  FIGS. 6 ,  8  and  10 . This tongue  28  and the catch  25  is preferably in one embodiment, in one piece with the wall  29  of the cannula cover  7  by providing slits into the wall which define the tongue. Further protruding ribs  30  may be provided on the outside of this wall  29  to provide sliding guides for the cannula cover  7  within the holder  4  that is provided in this case with corresponding groves or slits taking up these sliding guides. 
     The cannula holder  4  is provided with a hole or recess  31  for taking up the block-shaped step  27  of catch  25  (and in the case of several catches/tongues is provided with the same number of corresponding holes  31  for the block-shaped steps of these catches). In one embodiment, the recess  31  may be a hole. When the cannula cover  7  is mounted in the cannula holder  4  and the cover  7  is in the first locked state covering the cannula, then the block-shaped step  27  of catch  25  sits in the correspondingly shaped hole  31 . In this position, for example, shown in  FIGS. 1 and 6 , the cannula cover is thus locked against movement. When the cannula holder  4  is inserted into the adapter or receiving element  10 , then the release will remove the catch  25  from this locked position, allowing the moving of the cannula cover  7  during the insertion of the cannula holder  4  into the receiving element  10 . In the shown example, the rib  16  (and in the case of several catches  25 , the correspondingly placed several ribs  16 ) on the inside of the receiving element  10  first slides within a groove  32  of the cannula holder  4  leading to the hole  31 . Then, when the insertion of the cannula cover  7  into the receiving element  10  proceeds, rib  16  contacts the wedge-shaped, narrower step  26  of catch  25  that protrudes into groove  32  ( FIG. 10 ). Rib  16  then forces the catch  25  inwardly (e.g., in direction towards the cannula  5 ), thereby elastically deforming the tongue  28 , which frees the block-shaped step  27  from hole  31  such that the cover  7  can slide upwards (away from the tip of the cannula  5 ). During the upward movement step  26  of catch  25  is sliding within longitudinal slit  33  of the cannula holder  4  that connects to hole  31 . When the cannula cover  7  is fully moved backwards (which, as well, corresponds with the full insertion and the blocking of the cannula holder  4  in the receiving element  10  by the blocking element  20  as explained above) the position of  FIG. 11  is taken in which the rib  16 , the wedge-shaped, narrower step  26 , and the inwardly bent tongue  28  (bending shown only for the right tongue in the Figure) can be seen. When the blocking elements  20  are unblocked and the cannula holder  4  is pulled out of receiving element  10 , rib  16  moves accordingly downwards (in direction towards the tip of the cannula) and the cannula cover  7  is pressed downwardly by the coil spring or energy storage device  8  as well. During this downward movement, catch  25  again reaches hole  31  where the block-shaped step  27  of catch  25  again enters the hole  31  due to the spring back elasticity of the tongue  28 . Thus, cover  7  moves during the pull out movement over the cannula  5  again, covering the same more and more until once again the cover  7  is locked in the state of fully covering the cannula  5  when the cannula holder  4  is fully removed from the receiving element  10 . Thus, a fool prove cannula cover results having a fully automatic function both during insertion of the cannula holder into the receiving element and during pulling out of the cannula holder from the adapter or receiving element  10 , and thus also into and from device  2 . In the fully inserted state shown in  FIGS. 5 and 7 , the cannula  5  has pierced the reservoir  3  (and in case of an ampoule, the septum  39  thereof) so that a fluid connection between reservoir  3  and line  6  is provided by means of the cannula  5 . 
     With reference to  FIGS. 12 to 21 , another embodiment of the invention is now described. Same reference numerals as before depict same elements or functionally equivalent elements. In this illustrated embodiment, the connection system  1  may comprise a receiving element  10  that is not an adapter but rather forms a part of the device  2  itself.  FIG. 12  shows a sectional view through a device  2 , but of which only the functional elements relevant for the connection system are shown. In one embodiment, the device  2  may be a portable medical pump, and in another embodiment, the device  2  may be an insulin pump. Within the device,  2  a reservoir  3  in form of an ampoule can be placed which is in fluid connection with line  6 ′,  6  by means of cannula  5 . It is to be appreciated that the cannula  5  pierces the septum  39  of the ampoule or reservoir  3  when the cannula holder  4  is inserted into the receiving element  10 , which may be also part of device  2 . The building elements of this embodiment are now explained in greater detail. 
       FIG. 13  shows the “empty” device  2  without an ampoule  3  and the cannula holder  4  pulled out of the device. The cannula holder  4  has essentially an L-shape wherein the cannula  5  stands in a 90-degree angle to the line  6  as its exits the holder  4 . The straight cannula  5  is connected to the line  6  for example via a curved conduit  6 ′ and a valve  58  may be present between the conduit  6 ′ and line  6 , allowing a fluid flow only by pressure of the pump. The part of the holder  4  where the cannula  5  is held and the cannula cover  7  are still essentially cylindrical parts but may be of different shape as well. 
     As shown in  FIG. 14 , the receiving element  10  may comprise, for example, a sliding lid  45  which is slidable with regard to the part  48  for taking up the cannula holder  4 . The sliding lid  45  may comprise catch mechanisms  45 ′ for holding the sliding lid  45  shut and for allowing the opening thereof by the user. As the design of mechanisms  45 ′ for a lid is well known to person in the art, no further explanation is provided herein. The preferred receiving element  10  of this embodiment is further provided with an axis  55  that, after sliding the lid  45  to its opening position allows a swiveling motion of the receiving element  10  ( FIG. 15 ) to open the reservoir chamber  46  of the device  2  into which the ampoule can be inserted ( FIG. 16 ). The receiving element  10  is then swiveled back ( FIG. 17 ) and the lid  45  is slid closed, so that the ampoule  3  is enclosed in the device ( FIG. 18 ). In this embodiment, the release uses at least one rib  16  as well, but this rib is provided by two rib sections  16 ′ and  16 ″ on the ampoule seat  48  and the sliding lid  45 , respectively. The two rib sections  16 ′ and  16 ″ align to rib  16  when the lid  45  is closed ( FIG. 18 ). The lid  45  is held in its closed state for example by snapping means as catch mechanisms  45 ′. The pump user can use any kind of closing means that allow an easy closing and of course opening of the reservoir chamber  46 . At the same time, the receiving element  10  and the closing means on this element must obviously be designed to hold the ampoule or reservoir  3  firmly in place while the pump is pressing liquid out of the ampoule and—via cannula  5 —into line  6 . The pump is, for example, working by a motor and spindle drive for a piston provided within the ampoule at the other end of the ampoule facing away from the cannula. This way of driving the fluid out of the ampoule is known in the medical pump art and is therefore not explained in detail here. The design of a cover for the chamber  46  that can be opened and closed, and which at the same time provides the second part  10  of the connection system for inserting the cannula holder  4  and holding the ampoule or reservoir  3  in place, can be chosen in different ways by the person skilled in the art. Accordingly, as explained so far and shown in the drawings, the sliding lid  45  and swivable element  10  is a preferred example only. 
     Now, referring again to  FIG. 18 , the rib  16  is ready to act on the lock for the cannula cover  7  of the cannula holder  4 . The rib  16  is an example for the release in one embodiment, which in some embodiments, at least two of such ribs facing each other on the inner circumference of the cylindrical seat  48  for the cannula holder are provided. In the illustrated embodiment of  FIG. 18 , the lock is preferably constructed identically as explained in the former embodiment of  FIGS. 1 to 11 . Thus, for the second embodiment shown by  FIG. 19  (showing an exploded view and an assembled view of cannula holder  4  in the same Figure), the cannula holder is shown with the two stepped catch  25  within hole  31  as well and with groove  32  for the rib and slit  33  for the second, narrower step  26 . The function of the lock and release is therefore identical with the first embodiment discussed above previously. 
     In one embodiment, the cannula cover  7  is provided with a two-step catch  25  having a narrower, wedge shaped step  26  and a wider, block-shaped step  27  and in other embodiments, with two such catches  25  that may be arranged opposed each other along the circumference of the cover  7 . In still other embodiments, two or more of such catches  25  may be provided around the circumference of the holder  4 . In some of the embodiments, each catch  25  is formed at the end of an elastic tongue  28 , which allows the catch to be bent in inward direction of the cannula cover, as seen in  FIG. 11  and to spring back into its rest position shown in  FIGS. 6 ,  8  and  10 . This tongue  28  and the catch  25  can be in one piece with the wall  29  of the cannula cover  7 . Further protruding ribs  30  may be provided on the outside of this wall  29  to provide sliding guides for the cannula cover  7  within the holder  4  that is provided in this case with corresponding groves or slits taking up these sliding guides. The cannula holder  4  is provided with the hole  31  for taking up the block-shaped step  27  of catch  25  (and in the case of several catches/tongues is provided with the same number of corresponding holes  31  for the block-shaped steps of these catches). 
     When the cannula cover  7  is mounted in the cannula holder  4  and the cover  7  is in the locked state covering the cannula, then catch block-shaped step  27  of catch  25  fits in the correspondingly shaped hole  31  and the cannula cover is thus locked against movement in this position, for example, as shown in  FIGS. 1 and 6 . When the cannula holder  4  is inserted into the receiving element  10 , then the release will remove the catch from this locked position, allowing the moving of the cannula cover  7  during the insertion movement of the cannula holder  4  into the receiving element  10 . In the shown example, the rib  16  (and in the case of several catches  25 , the correspondingly placed several ribs  16 ) on the inside of the receiving element  10  first slides within a groove  32  of the cannula holder  4  leading to the hole  31 . Then, when the insertion of the cannula cover  7  into the receiving element  10  proceeds, rib  16  contacts the wedge shaped, narrower step  26  of catch  25  that protrudes into groove  32  (as explained before with reference to  FIG. 10 ). The rib  16  then forces the catch  25  inwardly (in direction towards the cannula  5 ), thereby elastically deforming tongue  28 . By this inwardly forcing, block-shaped step  27  frees from hole  31  and the cover  7  can slide upwards (away from the cannula tip). During the upward movement, step  26  of catch  25  is sliding within slit  33  of the cannula holder  4  that connects to hole  31 . 
     When the cannula cover  7  is fully moved backwards (which, as well, corresponds with the blocking of the cannula cover in the receiving element  10  by the blocking element  20  explained above), the position of  FIG. 11  is taken, wherein the inwardly bent tongue  28  and step  26  and rib  16  can be seen. When the blocking elements  20  are unblocked and the cannula holder is pulled out of receiving element  10 , rib  16  moves accordingly downwards (in direction towards the tip of the cannula  5 ) and the cannula cover  7  is pressed downwardly by coil spring or energy storage device  8  as well. During this downward movement, catch  25  again reaches hole  31  where the block-shaped step  27  of catch  25  again enters the hole due to the spring back elasticity of the tongue  28 . Thus, cover  7  has moved, during the pull out movement, over the cannula  5 , thereby covering same more and more until the cover  7  is again locked in the state of fully covering the cannula when the cannula holder  4  is fully removed from the receiving element  10 , and thus from device  2 . Thus, a fool-prove cannula cover results with a fully automatic function both during insertion of the cannula holder into and pulling out of the cannula holder from the receiving element, and thus from device  2 . In the fully inserted state shown in  FIG. 12 , the cannula  5  has pierced the reservoir  3  (and in case of an ampoule, the septum  39  thereof) so that a fluid connection between reservoir  3  and line  6  is provided by means of the cannula  5 . 
     The blocking and unblocking elements of this embodiment could have been selected identical to the blocking and unblocking elements of the first embodiment but have been selected differently from the first embodiment. Here, two latches  50  and  51  are provided on the lower outside of the horizontal part of the L-shaped cannula holder  4 , as can be seen in  FIGS. 19 and 20 . When the cannula holder  4  is inserted into the receiving element  10 , these latches  50  and  51  snap into a hole  56  within plate  52  of the cover when the cannula holder  4  is fully inserted into device  2 , as can be seen in  FIG. 21 . To unblock the cannula holder  4 , the two latches  50  and  51  are pressed together by a V-shaped lifter  53  that can be manually actuated by a knob on the outside of the pump housing against the force of spring  57 . In this manner, the latches  50  and  51  come free of plate  52 , which are then pressed upwardly to unblock the cannula holder  4 .  FIG. 22  shows the action of the lifter  53  that has already pushed the latches  50  and  51  away from the plate  52 . 
     With reference to  FIGS. 23 and 24 , a further embodiment is described with different means for blocking and unblocking of the cannula holder.  FIG. 23  shows an exploded view of the cannula holder  4  and the receiving element  10  which is here again of the adapter type. The cannula holder, the lock, and the release for the cannula cover are of the same construction as described for the first embodiment and reference is made to this description above. The blocking and unblocking elements, on the other hand, may comprise at least one recess  60  in the outer wall of cannula holder  4  and at least one corresponding finger  61  on the adapter or receiving element  10  that is arranged to reach into the recess  60  when the cannula holder  4  is fully inserted into the adapter or receiving element  10 . In this manner, the cannula holder is blocked within the adapter  10  by the finger. The embodiment shown in  FIGS. 23 and 24  comprises two recesses  60  and two corresponding fingers  61 . The fingers  61  reach so far through slit-shaped holes  63  in the wall of seat  48  of adapter or receiving element  10  so that they can enter the recesses  60 . On the other hand, the fingers  61  are connected to knobs  62  that can be pressed together by the user. By this pressure, the fingers  61  make a movement away from the cannula holder  4  and its recesses  60  and the cannula holder  4  is unblocked and will be pushed out of seat  48  and thus out of adapter or receiving element  10  by the force of the spring or energy storage device  8 . 
       FIGS. 25 and 26  show another embodiment wherein no energy storage element  8  is provided. In this embodiment, the cannula cover  7  is provided with a screw thread shaped protrusion  65  that is guided in a corresponding screw thread shaped guiding slit  66  in the wall of the cannula holder  4 . Thus the cannula cover  7  will be move backwards in a rotating movement when the lock here provided by at least one catch  67  (similar to the catch  25  of the other embodiments) are unlocked by the release which are provided here as well by a rib or ribs  16 . The rib or ribs  16  prevent, on the other hand, a turning of the cannula holder  4  with the guiding slit. In this manner, the cannula cover  7  when pushed backwards only rotates by abutting either on the adapter ground  68  or on the ampoule  3  while the cannula holder  4  is inserted into the adapter or receiving element  10  and the screw thread-shaped guide  65 ,  66  forces the rotating movement. The cannula  5  is exposed by the rotating backwards movement of the cannula cover  7 . As well, by the rotating movement of the cannula cover  7 , noses  69  on this cover rotate and enter by this turning movement below protrusions  71  on the inside wall of seat  48  of the adapter or receiving element  10 . The cannula cover  7  is therefore held within adapter or receiving element  10  against pulling out from the adapter or receiving element and thus, when the cannula holder  4  is again pulled out from the adapter or receiving element  10 , the cannula cover  7  is pulled over the cannula  5  again by making the rotating movement by the guide  65 ,  66  in opposite direction compared to the insertion. By this rotating movement, the cannula cover  7  is finally free again from protrusions  71  since noses  70  turn free from these protrusions by the rotating movement as well, so that the cannula holder  4  with the cover  7  can be pulled out of the adapter or receiving element  10 . The blocking and unblocking elements of this embodiment can be similar to the corresponding means of the first embodiment. Different blocking and unblocking elements are shown in  FIGS. 25 and 26 . Catches  73  are provided on the adapter or receiving element  10  that are arranged to fit into recesses  74  on the outside of the cannula holder  4  when this holder is fully inserted into the adapter or receiving element  10 . A wedge  75  on the unblocking element is adapted to force the catches  73 , which are correspondingly wedge-shaped, out of the recesses  74  when the cannula holder  4  shall be unblocked from the receiving element  10 , as has generally be explained before. The details of such a blocking element and an unblocking element are not shown for this embodiment, since the detail construction of such means can easily be conceived by the skilled person.