Abstract:
A device for applying active substances onto surfaces of medical implants, in particular stents, consists of a base station, and of an exchangeable cartridge which can be mounted on the latter. Provided on the cartridge there is a holder for the stents, and a nozzle for spraying the active substance onto the surface of the stent. Provided on the base station there is a drive unit via which the holder and the nozzle are moved relative to one another.

Description:
RELATED APPLICATION 
     This is a continuation of copending international patent application PCT/EP 2004/003942 filed an Apr. 15, 2004 and designating the US, which has been published in English as WO 2004/091684 A1 and which claims priority of German patent application No. 103 18 803.7, filed on Apr. 17, 2003. The contents of the above applications are incorporated by reference in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device for applying active substances to surfaces of medical implants, in particular stents, with a holder for the implants, an arrangement for applying the active substance onto the surface, and a drive unit for moving the holder and the arrangement relative to one another. 
     2. Related Prior Art 
     Such a device is known from U.S. Pat. No. 6,395,326 and from DE 202 00 223 U1. 
     The known devices are provided for coating stents, that is to say vascular prostheses, with medicaments. Such coatings are desirable because, in the first instance, they can improve the biocompatibility of the implants, for example so as to prevent development of thromboses in the case of surfaces coming into contact with blood. 
     Particularly in the case of stents, it is also known to coat their surfaces with medicaments, for example rapamycin, in order to prevent restenosis through proliferation of the surrounding tissue. Moreover, suitably coated stents are able to deliver medicaments in a targeted manner in situ into the surrounding tissue. 
     Stents which can be provided with a coating of different active substances have been described by many authors in the prior art; see, for example, DE 202 00 220 U1, EP 0 875 218 A2 or EP 0 950 386 A2. 
     Other medical implants also often require a suitable surface coating because they have to be biocompatible and their surfaces do not provide for this in the original state. Thus, in the context of the present application, an implant is to be understood as meaning not just prostheses which remain permanently in the patient&#39;s body, but also other devices which remain in the body for some time, for example pace makers, heart catheters, any kind of catheter, screws for orthopedic application, long-term catheters, which are used for intra-venous feeding, etc., of seriously ill, paralyzed or unconscious patients, and the like more. 
     In the aforementioned, known devices, the active substance is sprayed via a nozzle onto the outer surface of the stent, where it settles and dries on. To do this, a relative movement between nozzle and stent is needed in the longitudinal direction of the stent, and the stent has to be rotated in the jet of the nozzle, or the nozzle has to be rotated. 
     It has been found now that the known devices in many respects do not satisfy the latest requirements when using implants in general, in particular stents, and they especially do not satisfy the increasingly necessary or desired flexibility and individual adaptability in the coating. In addition, the known devices are not safe enough in terms of their use by the physician because the latter may come into contact with the active substances, which entails great risks, for example in the case of coatings with adenoviruses. Finally, the known devices are unsatisfactory purely from the point of view of mechanics, hygiene and sterility. 
     SUMMARY OF THE INVENTION 
     In view of the above, it is an object of the present invention to make available a novel device which is of the type mentioned at the outset and which avoids these disadvantages. 
     According to the invention, one object is achieved with a device of the type mentioned at the outset, which comprises a base station and an exchangeable cartridge which can be mounted on the latter, the drive unit being provided on the base station, and the holder and the arrangement being provided on the cartridge. 
     One object underlying the invention is completely achieved in this way. 
     The inventors of the present application have in fact found that this two-part design, with a reusable base station and disposable cartridges, affords many advantages. On the one hand, the novel device can be used in the catheter laboratory, so that the physician can decide on the spot as it were, and depending on the particular situation, which active substances and which dose are to be used to coat the implant for the patient concerned. 
     A further advantage here is that it is possible, during the operation on the patient, to make a decision as to which implant is to be used with which coating. The novel device permits a very rapid coating, so that valuable time is not lost through too long a coating procedure. A coating directly before introduction of the implant has the further advantage that a long storage time of the coated implants is avoided. 
     Overall, the novel device thus permits a sterile coating procedure directly in the catheter laboratory. 
     The cartridge is used only once, so that many implants can be coated in succession without extensive cleaning measures, and without the risk of cross-contamination occurring. The cartridge can be designed as a component closed off from the outside, so that the physician comes into contact only with the base station and with the new, sterile cartridge. After coating, the implant is removed and the cartridge is discarded, thus obviating the need to clean the nozzle and holder and avoiding the problems and risks associated with this. This is also particularly advantageous if the coating contains toxic substances. 
     According to another object the cartridge has a carriage, preferably a spray carriage which is mounted so that it can move in a longitudinal direction and which is in engagement with the drive unit when the cartridge is mounted on the base station. 
     It is of advantage here that, apart from a fluid connection that may possibly be required, the only connection between base station and cartridge is the connection between spray carriage and drive unit, so that the cartridge can therefore be sealed off effectively from the outside. It is further of advantage that the cartridge is less expensive than it is if it has to be equipped with its own drive unit. 
     In this connection, it is preferable if the arrangement comprises a nozzle for spraying the active substance onto the surface, the arrangement being preferably provided on the carriage. 
     It is of advantage here that it is the arrangement or nozzle that is moved, not the implant, so that it is also possible to coat bulky implants, for example stents already crimped onto a catheter, which could be moved only with some effort relative to a stationary nozzle or arrangement. 
     The nozzle is—according to another object—a first annular nozzle which surrounds the circumference of an implant mounted in the cartridge, it then being further preferred if the first annular nozzle is formed on a first wall of the spray carriage extending transversely with respect to the longitudinal direction, preferably through channels which are distributed symmetrically in a circumferential arrangement and end in a through-hole which surrounds the mounted implant and is provided in the first wall. 
     It is of advantage here that the number of moved parts can be kept very low. The annular nozzle is only moved in the longitudinal direction with respect to the implant, the circumferential distribution of the sprayed-on active substance is effected via the channels, and it is not necessary for the nozzle to rotate, so that possible damage to the coating is avoided which can arise if the nozzle or even the implant is moved in rotation. 
     The inventors of the present application were able to show that, with a symmetrical circumferential arrangement of the individual nozzles, it is possible to apply an also radially very uniform coating onto the top surface of the implant. 
     It is generally preferred if an active substance reservoir in fluid communication with the first annular nozzle is provided on the spray carriage, preferably on the first wall of the latter. 
     It is of advantage here that the active substance is not delivered by the base station, so that the latter is exposed to less risk of contamination. 
     A plug connection in fluid communication with the first annular nozzle is preferably provided on the spray carriage, preferably on the first wall of the latter, said plug connection being provided for an exchangeable syringe which holds the active substance or a solution containing the latter. 
     It is of advantage here that commercially standard syringes can be used as active substance reservoir, whereby it is possible, with one and the same cartridge, to apply different active substances in succession to the implant, and only the syringe has to be changed each time. 
     In this connection, a limit stop for a piston of the syringe is provided on the base station. 
     This measure is of advantage from the design point of view because the active substance is conveyed into the nozzle simultaneously via the movement of the spray carriage, and a separate drive is not needed for the syringe piston, the active substance being delivered at the same time as the nozzle is moved along the implant. 
     According to one development, the cartridge is provided with a second nozzle which, via the base station, is in fluid communication with a reservoir for a drying agent. 
     It is of advantage here that the cartridge can be used not just for applying the coating, but also for drying the coating, without having to exchange any components. This generally permits rapid coating of the implant, since the drying is accelerated. The drying agent can be compressed air, as is available in the catheter laboratory, delivered via a sterile filter. 
     According to another object, the second nozzle is also a second annular nozzle which is formed on a first wall of the spray carriage extending transversely with respect to the longitudinal direction, preferably through channels which are distributed symmetrically in a circumferential arrangement and end in a through-hole which surrounds the mounted implant and is provided in the first wall. 
     It is also of advantage here that the number of moved parts can be kept very low. The annular nozzle is moved only in the longitudinal direction with respect to the implant, the circumferential distribution of the drying agent is effected via the channels, and it is not necessary for the nozzle to rotate. 
     In another embodiment, seen in the longitudinal direction, the second annular nozzle is arranged behind the first annular nozzle on the first wall. 
     This measure too affords advantages in terms of time, since the drying takes place immediately after the active substance has been sprayed on. It is not necessary to couple the second annular nozzle to a separate drive or to move it in a second operation past the implant. By this measure, the number of moved parts in the cartridge is further reduced. 
     In another embodiment, it is further preferred if, between base station and cartridge, at least one sterile filter is provided via which a drying agent can be conveyed into the cartridge when said cartridge is mounted on the base station, the sterile filter preferably being connected to the second nozzle. 
     It is of advantage here that compressed air available in the catheter laboratory can be used for drying. The sterile filter can be connected to the cartridge and convey sterile air into the inside thereof, and the sterile filter can also be connected to the second nozzle so that the compressed air delivered is used directly for drying. It is also possible to use two sterile filters, of which one is connected directly to the second nozzle and the other to the cartridge interior. 
     According to another object it is preferred if a transport carriage which can be moved via the drive unit is provided on the base station, said transport carriage being connected to the spray carriage when the cartridge is mounted on the base station, the sterile filter being preferably connected at its first end to the spray carriage and, with the cartridge mounted on the base station, being connected at its second end to the transport carriage. 
     It is of advantage here that the connection between spray carriage and transport carriage is effected by the sterile filter or sterile filters. Thus, mounting the cartridge on the base station is very simple, and at the same time the attachment of the sterile filters also produces the mechanical connection for driving the spray carriage. 
     For mechanical reasons and also for reasons relating to sterility, it is preferred if two sterile filters are provided which are connected at their first end to the spray carriage and, with the cartridge mounted on the base station, are connected at their second end to the transport carriage. 
     Finally, it is also preferred if the cartridge is closed off from the outside, and at least one further sterile filter is provided on the cartridge, via which further sterile filter the cartridge is in fluid communication with its environment. 
     It is of advantage here that a sterile coating process is possible directly in the catheter laboratory, even if the coating contains toxic substances. 
     It is generally preferred if the cartridge has, at its end face, a first clamp unit as a holder for the implants, the cartridge preferably being provided with a second clamp unit as a holder for a protective sleeve surrounding the implants, said second clamp unit being able to move relative to the implant in the longitudinal direction in order to remove the protective sleeve from the implant. 
     It is of advantage here that implants with protective sleeve can be coated without it being necessary to remove the protective sleeve, before fitting the implant, and then reapply the protective sleeve. This ensures, inter alia, good sterility and protects the physician and also the coating during removal of the finished coated implant. 
     The second clamp unit is preferably formed on the spray carriage, said second clamp unit preferably being formed at a second wall of the spray carriage remote from the end face, and the first and second walls further preferably having a distance from one another, in the longitudinal direction, which is greater than the implant in its longitudinal extent. 
     These measures are of advantage from the design point of view, because no separate drive is needed for removing the protective sleeve, and the number of moved components is thus further reduced. Moreover, the number of movements needed for coating is reduced, because the protective sleeve is at first gradually drawn off during the movement of the spray carriage and pushed back on again upon reversal of the spray carriage. The distance between first wall and second wall allows the protective sleeve to be drawn off from the implant by a small predetermined distance upon assembly in the cartridge. In this way it is possible, at the end of the coating process, to return the spray carriage past its start position and thus completely push the protective sleeve on, and to use this travel to open the clamp units, so that the implant can be removed from the cartridge without this having to be opened again. 
     In a further development, the first clamp unit is designed to receive a catheter carrying a stent, and the second clamp unit is designed to receive a protective sleeve fitting over the stent. 
     In yet another embodiment the base station is provided with a first sensor which indicates when the spray carriage is situated in a start position in which the syringe can be mounted or exchanged, the base station preferably being provided with a second sensor which indicates when the spray carriage is situated in its end position in which the syringe is emptied. 
     It is of advantage here that the movement patterns are monitored by sensors, which have to be provided just once, and in this way too the cartridge is structurally simple and thus inexpensive. 
     According to another object, an unlocking arrangement is provided for the first and second clamp units, which unlocking arrangement automatically releases the implant when the spray carriage is moved past its start position, adopted upon mounting of the implant, towards the first end face. 
     In this way, the implant is released automatically, so that the cartridge no longer has to be opened after coating is completed. This measure thus not only serves to increase the speed of coating, it also protects the coating and the physician. 
     It is preferred here if the unlocking arrangement for the first clamp unit is arranged between the first end face and the unlocking arrangement for the second clamp arrangement. 
     This ensures that the protective sleeve is pushed on completely when the implant is released. 
     It is further preferred if the base station is provided with a third sensor which indicates when the spray carriage is situated in a removal position, in which the first and second clamp units are unlocked, so that the implant can be removed. 
     It is also of advantage here that the sensor is arranged on the base station. 
     Overall, the novel device permits rapid, reliable and safe coating of implants of different lengths, and the cartridge to be used just once has only one moved part, namely the spray carriage. The cartridge is thus inexpensive to produce. In addition, the novel device is easy to operate. 
     It is further of advantage that, in a single linear movement, the content of a syringe can be applied to the surface of the implant and dried. This procedure can, if appropriate, be repeated with a syringe containing a new medicament. The physician can decide on the spot about the nature and dose of the active substance to be incorporated in the coating. 
     A further object of the invention relates to a cartridge for the novel device. This cartridge is designed as a disposable article and has the features already described in connection with the novel device. 
     A further object of the invention relates to a base station for the novel device. This base station is re-usable and has the features already described in connection with the novel device. 
     A further object of the present invention refers to a kit containing a new cartridge and at least one syringe. The syringe through which the active substance is delivered is supplied in the kit together with the cartridge. The syringe too can be designed as a disposable article. In this way, the physician not only has the cartridge to hand, but also the appropriate syringe. 
     Further advantages and features will become apparent from the following description and from the attached figures. 
     It will be appreciated that the features explained above, and those still to be explained below, can be used not just in the respectively stated combination, but also in other combinations or in isolation, without departing from the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are set out in more detail in the following description with reference to the figures, in which: 
         FIG. 1  shows a diagrammatic plan view of the base station of the novel device; 
         FIG. 2  shows a diagrammatic plan view of the cartridge provided for the base station from  FIG. 1 ; 
         FIG. 3  shows a perspective view of a base station with inserted cartridge; 
         FIG. 4  shows a perspective side view of the connection between base station and cartridge via sterile filters; 
         FIG. 5  shows a perspective view of the cartridge from  FIGS. 2 to 4  from above, and with the cover removed; 
         FIG. 6  shows a sectional plan view of the cartridge from  FIG. 2 , in the start position; 
         FIG. 7  shows a view as in  FIG. 6 , the spray carriage being in the coating position; 
         FIG. 8  shows a view as in  FIG. 6 , the spray carriage being in the position when coating has ended; 
         FIG. 9  shows a view as in  FIG. 6 , the spray carriage now being in the position for catheter removal; and 
         FIG. 10  shows a perspective view of the first annular nozzle used in the cartridge from  FIG. 2 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     In  FIG. 1 , reference numeral  10  designates a base station of the novel device, and  FIG. 2  shows a cartridge  11  to be fitted into the base station  10  from  FIG. 1 . A catheter  12  is fitted into the cartridge  11 , said catheter  12  having, at its front end, a stent which is designated by  14  and which is intended to be coated with an active substance via the novel device consisting of base station  10  and cartridge  11 . At its other end, the catheter  12  is held in a screw conveyor indicated by  15 . 
     The cartridge  11  has a housing, indicated by  16 , which is sealed off in a sterile manner from the outside and, during coating of the stent  14 , prevents contamination with the active substance in the laboratory in which the coating is taking place. 
     The cartridge  11  is supplied in the format shown in  FIG. 2 , that is to say with the catheter  12  secured on it, and is fitted into the re-usable base station  10  present in the catheter laboratory, for the purpose of coating the stent  14 . 
     A spray carriage  17  is arranged in the cartridge  11  and can move to the left and right in  FIG. 2 ; a syringe  21  sits in a plug connection  19  on the first wall  18  of the spray carriage  17  protruding laterally from the housing  16 , into which syringe  21  a medicament indicated by  22  has been drawn which is intended to coat the stent  14 . For this purpose, the piston  23  is pushed into the syringe  21 , in a manner to be described in greater detail, by which means the medicament  22  passes through channels provided in the first wall  18  to a nozzle (not shown in  FIG. 2 ) which surrounds the stent  14 . 
     In the cartridge  11  there is also a holder for the catheter  12 , said holder being indicated by  24 , while a second wall  25  of the spray carriage  17  at a distance from the first wall  18  has a holder, indicated by  26 , for a protective cap (not shown in  FIG. 2 ) provided on the stent  14 . 
       FIG. 2  also shows two sterile filters  27  and  28  which, in the plan view in  FIG. 2 , lie under the housing  16  and are in fluid communication, in a manner to be described in more detail, with the first wall  18  of the spray carriage  17 . 
     The cartridge  11  described thus far, with screw conveyor  15 , can be fitted into the base station  10  shown in  FIG. 1 , said base station  10  having a box-shaped bottom part  31  in which a support plate  32  for the screw conveyor  15  is provided. The support plate  32  is provided with a window  33  underneath which a receiving plate  34  for the cartridge  11  can be seen. 
     Two oblong holes  35 ,  36  can be seen in the receiving plate  34 , these oblong holes  35 ,  36  extending in a longitudinal direction indicated by an arrow  37 . 
     A transport carriage  38  is mounted displaceably in the longitudinal direction  37  underneath the receiving plate  34 . For driving the transport carriage  38 , a drive unit  39  is provided which comprises a step motor  41  and an output shaft  42  via which the step motor  41  is in operative connection with the transport carriage  38 . Attachments  43 ,  44  provided on the transport carriage  38  and intended for the sterile filters  28 ,  27 , respectively, can be seen in the oblong holes  35 ,  36 . The attachments  43  and  44  are provided via a flexible tube  45  with a compressed air connection  46 , via which compressed air usually provided in a catheter laboratory can be conveyed to the transport carriage  38  and from this through the two sterile filters  27 ,  28  to the inside of the housing  16  of the cartridge  11 . The flexible tube  45  is so dimensioned that it permits displacement of the transport carriage  38  in the longitudinal direction  37 . 
     On the receiving plate  34  there are also four locking elements  47  via which the cartridge  11  can be connected captively but releasably to the receiving plate  34 . These locking elements  47  can be locking projections, or alternatively locking apertures into which locking projections latch, and which are provided on the underside (not shown in  FIG. 2 ) of the housing  16  of the cartridge  11 . 
     Finally, at the bottom right of the receiving plate  34 , in the window  31 , there is a limit stop  48  for the piston  23  of the syringe  21 . 
     As has already been stated, the base station  10 , in its intended application, is located in a catheter laboratory where it is connected via its compressed air connection  46  to a compressed air source. This compressed air is used, in a manner to be described in more detail, as a drying agent for a coated stent  14 . Moreover, the base station  10  is connected in the normal way to the mains supply or to a suitable battery or suitable generator so as to drive, for example, the step motor  41 . 
     If, for example, in the course of an operation, a stent  14  is now to be coated with a certain medicament  22  and then implanted, a sterile-packed cartridge with screw conveyor  15  and matching stent  14  is taken from storage and is removed from its protective sheath under the sterile conditions in the catheter laboratory. The syringe  21  delivered together with the cartridge  11  is filled with the desired medicament and, if appropriate, with necessary additives, and is then inserted into the plug connection  19 . 
     The cartridge  11  is then placed on the receiving plate  34 , so that on the one hand it comes into engagement with the locking elements  47 , on which it is held captively, but exchange-ably. At the same time, the sterile filters  27  and  28  come into engagement with the attachments  44  and  43 , so that compressed air can pass into the inside of the housing  16  of the cartridge  11 . The screw conveyor  15  now lies on the support plate  32  in a receiving area indicated by  49 . 
     The spray carriage  17  is now connected to the transport carriage  38  via the sterile filters  27  and  28 , so that it follows the movement of the transport carriage  38  in the longitudinal direction  37 . Upon a movement of the spray carriage  17  in the longitudinal direction  37 , the syringe  21  is also moved to the right in  FIGS. 1 and 2 , as a result of which the piston  23  comes into contact with the limit stop  48 . If the transport carriage  38  and thus the spray carriage  17  are moved farther to the right, the piston  23  is thereby pressed into the syringe  21 , as a result of which the medicament  22  passes, in a manner to be described in more detail, through channels in the first wall  18  and into the inside of the housing  16  where it ensures coating of the stent  14 . In other words, as the spray carriage  17  moves to the right, it covers the area of the stent  14  to be coated, while at the same time, through continuous insertion of the piston  23  into the syringe  21 , suitable medicament  22  is sprayed onto the surface of the stent  14 . 
     When the coating of the stent  14  is completed and the sprayed-on medicament has been dried by the compressed air, the cartridge  11  with screw conveyor  15  is removed from the base station  10  which, without further cleaning measures, is immediately available for coating of a new stent. 
     The cartridge  11 , however, does not have to be opened, and, instead, the catheter  12  with the now coated stent  14  can be removed immediately, in a manner which will be described below. The remaining, still closed cartridge  11  with sterile filters  27  and  28  and syringe  21  is discarded. In this way, all parts of the coating device consisting of base station  10  and cartridge  11  which come into contact with the medicament  22  are used only once, so that each new stent is as it were delivered with its own new cartridge  11 . 
     In this way it is possible, with the novel device, to coat the stent  14  with a medicament  22 , that is to say any desired active substance, under sterile conditions in the catheter laboratory. If so desired, after coating with a first active substance  22 , the syringe  21  can be replaced by a new syringe with another active substance, so that the stent  14  can be coated in succession with different active substances or other substances. 
       FIG. 3  is a perspective view of the base station  10  from  FIG. 1 , with a cartridge  11  from  FIG. 2  mounted on it. The support plate  32  is partially cut away so that the transport carriage  38  and the step motor  41  can be seen. Moreover, the figure shows the sterile filter  28  which is provided under the cartridge  11 , and below which the oblong hole  35  extends. 
     The base station  10  is designed as a box whose lower part  31  can be closed by a lid  51 . The screw conveyor  15  lies in the receiving area  49  on the support plate  32 . 
       FIG. 4  shows a perspective view of the cartridge  11  from  FIG. 2  when mounted on the transport carriage  38  from  FIG. 1 . It can be seen that the transport carriage  38  is connected via the attachments  43  and  44  to the sterile filters  28 ,  27 , which in turn sit on the carriage  17  on which the syringe  21  is also secured, as is indicated at  21 . 
     The transport carriage  38  runs on a guide part  52  which in turn is mounted on a bottom plate  53  of the base station  10 . 
       FIG. 4  also shows that the only connection between base station  10  and cartridge  11  is via the two sterile filters  27 ,  28 , which permit the mechanical connection between spray carriage  17  and transport carriage  38  and also the sterile delivery of compressed air into the inside of the cartridge  11 . 
       FIG. 5  shows the cartridge  11  from  FIG. 2  in a perspective view from above, but with the housing  16  shown without its lid. In the housing  16  there is a further sterile filter  54  via which the cartridge  11  is in fluid communication with its environment. This ensures that medicament  22  sprayed into the cartridge  11  does not get into the environment. The cartridge  11  itself is closed off from the outside, so that, in the catheter laboratory, toxic medicaments can also be used to coat the stent  14 . 
     At its end face  57  on the right in  FIG. 5 , the cartridge  11  has first holder  24 , a first clamp unit  58  which clamps the catheter  12 . At the second wall  25  of the spray carriage  17  there is a second clamp unit  59  which clamps a protective sleeve, indicated at  61 , for the stent  14 . As the spray carriage  17  moves to the left in  FIG. 5 , the catheter  12  and the stent  14  mounted on it are secured by the first clamp unit  58 , while the protective sleeve  61  is drawn off from the stent  14  by the second clamp unit  59 , so that the stent  14  can be coated. During the travel of the spray carriage  17 , the first wall  18  moves in the longitudinal direction over the stent  14 , and in the first wall there is a through-hole  56  in which a nozzle, to be described in more detail, is present which sprays a medicament, delivered via the plug connection  19 , onto the surface of the stent  14 . 
     Both the first clamp unit  58  and the second clamp unit  59  comprise a clamp plate  62 ,  63 , respectively, which in each case fits in a transverse slit extending transversely with respect to the longitudinal direction  37  of the catheter  12 . Reference number  64  indicates a trans-verse slit of the second clamp unit  59 , in which the clamp plate  63  fits. 
     The clamp plates  62  and  63  are pressed against the bottom of the housing  16  of the cartridge  11 , as a result of which they exert a downward clamping action on the catheter  12  and protective sleeve  61 . 
     The spray carriage  17  has longitudinal carriers indicated at  65  which narrow in a wedge shape at their front end  66 . When the spray carriage  17  is driven to the right in  FIG. 5 , the wedge-shaped front ends  66  of the longitudinal carriers  65  pass under the clamp plate  62  and press the latter upwards, so that the catheter is freed from the first clamp unit  58 . 
     In the same way, the inside bottom  67  of the housing  16  is provided with wedges  68  which pass under the clamp plate  63  and push the latter upwards, so that the protective sleeve  61  is freed from the second clamp unit  59 , when the spray carriage  17  and with it its second wall  25  are driven far enough to the right in  FIG. 5 . 
     The arrangement is designed such that, upon a movement of the spray carriage  17  to the right in  FIG. 5 , the wedges  68  free the second clamp unit  59  even when the first clamp unit  58  is still in engagement. Only after the protective sleeve  61  has been freed from the second clamp unit  59  do the front ends  66  of the longitudinal carriers  65  pass under the clamp plate  62  so that the catheter  12  too is freed from the first clamp unit and can now be removed from the cartridge, for which purpose it is pulled out counter to the longitudinal direction  37 . In other words, this means that, after the end of the coating of the stent  14 , the spray carriage  17  moves to the right in  FIG. 5  and firstly pushes the protective sleeve  61  back onto the stent  14 . The protective sleeve  61  is then freed by loosening the second clamp unit  59 . Only now is the first clamp unit  58  freed, again by further movement of the spray carriage  17 , so that the catheter with the coated stent  14 , onto which the protective sleeve  61  has now once again been pushed completely, can be removed. It is therefore not necessary to open the housing  16  of the cartridge  11  in order to be able to remove the coated stent. Any medicament contamination present in the inside of the cartridge  11  is thus disposed of upon disposal of the cartridge  11 . 
     The fact that, during the travel of the spray carriage  17  to the right in  FIG. 5 , the second clamp unit  59  is freed first, and only thereafter the first clamp unit  58 , ensures that the protective sleeve  61  is pushed back completely onto the stent  14  before the catheter  12  itself is freed. 
     From what has been said, it will also be evident that the walls  18  and  25  of the spray carriage  17  have, in the longitudinal direction  37 , a distance from one another which is greater than the stent  14  in this longitudinal direction  37 . In this way, it is possible to initially draw the protective sleeve  61  partially from the stent  14  and then begin coating, as will now be described in detail with reference to  FIGS. 6 to 8 . 
     Provided in the first wall  18  of the spray carriage  17  there is a through-hole  56  through which the catheter  12  extends. The first holder  24  is situated to the left of the first wall  18  in  FIG. 5 , while the second holder  26  is situated on the second wall  25  facing the side of the first wall  18  remote from the first holder  24 . 
     In  FIGS. 6 to 8 , the cartridge  11  from  FIG. 5  is shown in sectioned plan views in different positions of the spray carriage  17 . In  FIG. 6 , the spray carriage  17  is in the start position in which the cartridge  11  can be mounted on the base station  10 . For the sake of clarity,  FIGS. 6 to 8  do not show the syringe  21  which, via a channel indicated at  71 , is in fluid communication with a further channel  72  which leads to a first annular nozzle  73  whose channels end in the through-hole  56  surrounding the catheter  12 . Viewed in the longitudinal direction  37 , a second annular nozzle  74  is situated on the first wall  18  to the left of the first annular nozzle  73 , and its channels likewise end in the through-hole  56 . The second annular nozzle  74  is in fluid communication, in a manner to be described in detail below, with a reservoir for a drying agent, and, in the illustrative embodiments shown, the drying agent is compressed air which passes from the compressed air connection  46  on the base station  10  to the sterile filters  27 ,  28  and from there to the annular nozzle  74 . 
     In the start position shown in  FIG. 6 , the protective cap  61  is still pushed over the stent  14  (not shown in  FIG. 6 ), and the two annular nozzles  73  and  74  are situated to the left of the protective sleeve  61 , viewed in the longitudinal direction  37 . 
     This position of the spray carriage  17  is detected by a first sensor, indicated at  76 , which is provided on the base station  10  and records the position of the transport carriage  38 . In this start position, a syringe can, as has been stated, be connected to the first wall  18  via the plug connection  19  shown in  FIG. 2 , in such a way that the medicament  22  passes through the channel  71  and the channel  72  to the annular nozzle  73  when the piston  23  is pushed into the syringe  21 . 
       FIG. 6  also shows the two clamp plates  62  and  63  which clamp the catheter  12  and the protective sleeve  61 , respectively. 
     In  FIG. 7 , by comparison with  FIG. 6 , the spray carriage  17  has been driven to the right, so that the protective sleeve  61  has been drawn partially from the now visible stent  14  clamped on the catheter  12 . The medicament is now sprayed through the first annular nozzle  73  onto the circumference of the surface of the stent  14 , the spray pressure being defined by the piston  23 , in contact with the limit stop  48 , being pushed into the syringe  21 . In other words, only a translation movement of the spray carriage  17  to the right in  FIG. 7  is needed in order both to dispense the active substance onto the surface of the stent  14  through the first annular nozzle  73  and also to drive the first annular nozzle  73  along the stent  14 . At the same time as the first annular nozzle  73  is moved, the protective sleeve  61  is drawn further from the stent  14 . 
     Since the second annular nozzle  74  is arranged behind the first annular nozzle  73  in the longitudinal direction  37 , the sprayed-on medicament is dried, directly after spraying, by the drying agent emerging from the annular nozzle  74 , that is to say compressed air that has been filtered to be substantially sterile. 
       FIG. 8  shows the position of the spray carriage  17  in which the stent  14  has been completely coated. The protective sleeve  61  has now been removed completely from the stent  14 , which is now finally dried by the compressed air emerging from the second annular nozzle  74 . This position of the spray carriage  17  is detected by a second sensor  77  which is likewise provided on the base station  10 . 
     After the drying procedure has ended, the spray carriage  17  is moved to the left in  FIG. 8  until it reaches the position shown in  FIG. 9 , in which the catheter  12  can be removed. This position lies to the left of the start position shown in  FIG. 6  and is detected by a third sensor, indicated at  78 , which is likewise provided on the base station. When the spray carriage  17  has assumed the position shown in  FIG. 9 , the second clamp unit  59 , as has already been discussed in connection with  FIG. 5 , was first opened via the wedge  68  as soon as the protective sleeve  61  was pushed back completely over the stent  14 . Upon further movement of the spray carriage  17  to the left in  FIG. 9 , the first clamp unit  58  was then opened via the front ends  66  so that the catheter  12  with protective sleeve  61  can now be pulled leftwards from the cartridge  11 . The cartridge  11  is then disposed of. 
     It should also be noted that the sensors  76 ,  77  and  78  are indicated in  FIG. 1  by small boxes sitting on the window  33  on the support plate  32 . It can be seen that the sequence in the longitudinal direction  37  is firstly sensor  78  (catheter removal position), then sensor  76  (start position) and, finally, sensor  77  (position when coating completed). 
     Finally,  FIG. 10  shows a perspective view of the first annular nozzle  73  which is clamped in the first wall  18 . The first annular nozzle  73  is a disc-shaped plate with the through-hole  56  into which spray nozzles  81  open which, via the channel  72  already known from  FIG. 6 , are in fluid communication with the channel  71  and, via the latter, with the syringe  21 . The active substance  22  is distributed through the channels  71  and  72  to the three spray nozzles  81  which open out symmetrically in the through-hole  56  and thus symmetrically surround the catheter  12  and stent  14 . 
     For the sake of clarity, the first annular nozzle  74 , designed in a similar way, is not shown in  FIG. 10 . 
     The second annular nozzle is supplied with compressed air via channels  82  and  83 , the channel  83  leading to a similar inner channel system and to similar compressed air nozzles as is indicated by the channels  72  and the spray nozzles  81  for the first annular nozzle  73 . 
     The second annular nozzle is connected via the channel  82  to the sterile filters  27  and  28 . 
     The second annular nozzle  74  also symmetrically surrounds the implant to be coated, so that medicament deposited on the surface of the latter is dried uniformly.