Abstract:
The invention relates to a cannula protector that serves to cover a cannula which has been attached to a syringe, particularly for the purpose of preventing unintended damage to the cannula as well as contamination of the cannula shortly before its use on the patient. The invention also relates to a single-use syringe system with such a cannula protector. 
     A cannula protector according to these principles includes a tubular sleeve and a bellows which, in part together with the sleeve, completely encloses at least the area of the cannula. The cannula protector usually also comprises a radially acting clamp or engagement spring, whose function is to hold the inserted single-use syringe in the desired position, or to activate the protective mechanism.

Description:
BACKGROUND 
     Various needle protection devices are known from the state of the art. The brief storage of single-use syringes that have been prepared for the injection, until the time of the performance of the injection, as well as the disposal of already used single-use syringes, is of particular importance because of the risk of infection with various pathogens, and because of the risk of damage to the exposed cannula. 
     From DE 100 44 383 C2 a needle protection device is known, which is used on a cannula which can be attached to a single-use syringe. The needle protection device comprises a carrier and a needle sleeve. The needle sleeve can be moved out of a retracted position into a protection position in which it envelopes the puncture needle at least up to the needle tip. The needle sleeve comprises a bellows, and locking elements which form a locking telescope that assumes a locking position in the deployed state. The needle protection device relates exclusively to the cannula which, after the use of a single-use syringe, can again be removed from the latter. 
     From EP 0 763 369 B1, a needle protection device with collapsing sleeve is known. The needle protection relates to a catheter where, as a collapsing sleeve, a bellows which can be moved against a spring force is used. The sleeve reliably and automatically protects the sharp tip of the introduction needle of the catheter, after the needle has been used for placing a catheter on a patient. The protection device has a complicated structure with many individual parts, and a complicated spring engagement mechanism for the activation of the protection mechanism. The bellows is formed from a flexible, impermeable, nonelastic material with low expansion properties. The individual parts of the protection sleeve are assembled in an elaborate way, for example, by press fitting, ultrasound welding, or the use of a standard glue. 
     From US 2004/0127857, a multipart cannula protector with an outer sleeve and an inner protection sleeve is known. Between the internal and external sleeves, elaborate mechanical means are provided in order to mutually fix the sleeves, for the purpose of the injection, and “countersink” the needle within the outer sleeve for the manual or automatic release of a resetting mechanism. In an embodiment, inside the inner sleeve, a spiral spring is integrally formed with the sleeve. 
     From U.S. Pat. Nos. 4,927,416 and 5,795,336 A, syringes with multipart needle protection covers are known, which act against a spring tension. 
     U.S. Pat. No. 4,738,663 A describes a lengthwise divided needle protection device which, for mounting on a syringe, presents a snap connection with a nose and groove. 
     In U.S. Pat. No. 4,737,144 A, a needle protection device to be moved onto a syringe is disclosed, which can be fixed by means of radial engagement elements or bayonet closure. 
     From FR 2 613 628 A, a single-use syringe is known. A closing mechanism with engagements and a predetermined breaking edge on the syringe plunger are intended to make it impossible to reuse the syringe. 
     SUMMARY 
     The invention is based on the problem of providing a cannula protector for the reliable covering of a cannula attached to a syringe, which cannula protector can be manufactured in large quantities in a particularly simple and cost effective way. The cannula protector should be designed preferably as a one-time use protecting sleeve and may be suitable for use on single-use syringes. To optimize the protection of used syringe parts against infection, a system with a cannula protector is also to be provided, which prevents the reuse of not only the cannula but also the single-use syringe. 
     The problem is solved by a cannula protector according to the attached claim  1 , and by a single-use syringe system according to claim  12 . 
     The cannula protector according to the invention presents a tubular sleeve for axially moveable accommodation of a syringe, preferably a single-use syringe. The tubular sleeve is closed at one of its ends by a base, where the base has an opening for the passage of a cannula attached to the single-use syringe. At the other end of the sleeve, a compressible spring element is constructed as a bellows, and is formed as a single piece, where the bellows presents a preliminary tension, so that it resumes its original shape after compression in the axial direction and subsequent release. 
     The sleeve and the bellows have dimensions in terms of total length such that the single-use syringe with attached cannula is completely enclosed by the cannula protector over its entire axial extent at least in the area of the cannula. The bellows must overall be capable of being compressed by approximately the length of the cannula, so that the cannula, when the single-use syringe is inserted for the purpose of the injection, can move substantially entirely out of the opening. Advantageously, the cannula protector is made available in various sizes and, in each case, with bellows of different lengths. 
     The sleeve length is shorter than the length of the syringe cylinder of the syringe to be inserted. The compression length is at least equal to the length of the cannula of the syringe to be inserted. The sum of the sleeve length and stretched length of the bellows is at least equal to the sum of the length of the syringe cylinder and the length of the cannula. 
     In the case of an axially directed pressure on the bellows, the single-use syringe is moved in the cannula protector, which results in the cannula being released through the opening in the base. 
     The cannula protector comprises, moreover, at least one radially acting clamp spring which is arranged in the area of the sleeve. Preferably several clamp springs are provided with uniform distribution over the periphery of the sleeve. 
     The clamp spring or the clamp springs can be actuated by the finger pressure of two fingers that grip the sleeve, in order to press the clamp spring(s) against the inserted single-use syringe, and to keep the latter in the instantaneous position. This is done for the purpose of injection, when the cannula extends out of the opening. 
     According to the invention, the bellows is under pressure, that is, when the syringe is moved with the cannula in the direction of the opening, the bellows can be pressed together, and as a result of spring elasticity it resumes its original shape after the release, namely when the clamp springs are released, particularly when the syringe is put down. 
     The advantages of the invention are particularly that the cannula protector can be manufactured in a particularly simple and cost effective way, for example, by an injection molding method. The cannula protector according to the invention can be used in connection with conventional syringes, without the need to have to change the design of the latter. 
     In a preferred embodiment of the invention, the bellows is in the shape of a screw. The latter can be manufactured preferably by the injection molding method using a rotating core which, after the casting, is twisted out of the finished cannula protector. In this way, the cannula protector can be removed easily from the mold, without having to be sectioned into several parts. Consequently, the entire cannula protector can be formed as a single part. 
     Advantageously, two clamp springs are arranged radially opposite each other, or four clamp springs are arranged with uniform distribution over the periphery. However, it is equally possible to select a different number of clamp springs. The clamp springs are preferably designed so they constitute a single piece with the sleeve, by forming tongue-shaped clamp springs which, to facilitate the actuation, present a section that protrudes beyond the wall of the sleeve. The—in each case radially opposite—positions of two clamp springs promote the actuation of the clamp mechanisms when the syringe is gripped with two fingers by the operator. 
     It is preferred that a scale of the inserted single-use syringe can be observed, in spite of the enclosing cannula protector. This can be achieved advantageously by one or more axially running slits in the sleeve. However, it is also possible to manufacture the cannula protector completely or in sections from a transparent plastic material. 
     The cannula protector can be designed as a single piece, or, in an advantageous embodiment, it can be divided into two in the axial direction, in such a way that it can be assembled by means of an engagement mechanism. 
     The opening for the passage of the cannula has preferably a circular shape, but other shapes, such as, for example, the shape of a cross, are also possible. 
     A particularly advantageous single-use syringe system comprises a cannula protector of the above-described type and a single-use syringe, where the single-use syringe or part thereof can be locked undetachably by means of a connection notch with the cannula protector. The single-use syringe system according to the invention prevents a new use of the single-use syringe inserted into the cannula protector. 
     In a preferred embodiment of the single-use syringe system, the plunger of the single-use syringe is provided with a predetermined breaking edge to prevent reuse, and, in the interior of the syringe cylinder, a flange which is narrowed in cross section close to the outlet is provided, which destroys the predetermined breaking edge as the latter strikes the flange, so that the plunger after use is no longer mounted with seal in the single-use syringe. 
     In a second preferred embodiment of the single-use syringe system, a closing mechanism is provided on an actuation system of the single-use syringe and on the cannula protector, which mechanism, after a one-time closing actuation of the syringe plunger, engages, and as a result prevents, a repeated use of the single-use syringe. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Preferred embodiments of the invention are explained in further detail below in reference to the figures. 
         FIG. 1  is a spatial view of a cannula protector; 
         FIG. 2  is a longitudinal cross-sectional representation of the cannula protector with inserted single-use syringe; 
         FIG. 3  is a spatial view of a second embodiment of the cannula protector; 
         FIG. 4  are three spatial detail representations of a cannula protector in a two-part design; 
         FIG. 5  is a detail view of a closing mechanism of a single-use syringe system; and 
         FIG. 6  is a detail view of a single-use syringe. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a cannula protector  01  in a spatial representation. The cannula protector  01  comprises a tubular sleeve  02 . The sleeve  02  is closed at its first end by a base  03 , which presents an opening  04  for the passage of a cannula  05  ( FIG. 2 ) of a single-use syringe  09  ( FIG. 2 ). The represented opening  04  has a circular shape. However, it is also possible to use other suitable shapes, such as, for example, a cross or the like. 
     A bellows  06  forms a single piece with an end of the sleeve  02 , which faces the base  03 . The bellows  06  is under a preliminary tension, and it can be pushed together or compressed under pressure in the axial direction. When the pressure is released, the bellows  06  resumes its original shape. The bellows  06  is preferably formed with a coiled wall, so that it works like a helical spring. The bellows  06  is represented here in the completely stretched state. The resetting force to be applied by the bellows in the compressed state must be sufficiently large so that the sleeve  02  is moved axially forward on the syringe and receives the cannula, as soon as no force is applied by the user to the entire system. At the same time, the counterforce of the bellows to be overcome during the injection should be as small as possible, so as not to make the injection more difficult. 
     Between the sleeve  02  and the bellows  06 , two projecting parts  07  are preferably arranged, which function to allow the holding of the cannula protector  01  with two fingers, when the single-use syringe is inserted into the cannula protector, or during the injection. 
     On the periphery of the sleeve  02 , in the represented embodiment, four radially-acting clamp springs  08  are arranged, which, when pressure is oriented radially on them, hold the inserted single-use syringe in the instantaneous position in the sleeve  02 , preferably with the cannula uncovered for the injection. 
     The arrangement of four clamp springs  08  distributed over the periphery has been found to be advantageous, because, as a result, the cannula protector  01  does not have to be rotated with inserted single-use syringe, to operate the clamp springs with two springs. The usual one-hand operation of the syringe also continues to be possible with the cannula protector  01 . 
     The clamp springs  08  are formed as springy tongues forming one piece with the sleeve  02 , and they have a radial overhang  10  for easier actuation. 
       FIG. 2  shows a longitudinal cross-sectional representation of the cannula protector  01  according to the invention, with a single-use syringe  09  inserted in it. The single-use syringe  09  comprises, in a known way, a syringe cylinder  11  with a nozzle  12  for the attachment of the cannula  05 . The single-use syringe  09  comprises, moreover, a syringe plunger  13  with an actuation plate  14  for pushing the syringe plunger  13  into the syringe cylinder  11 . 
     The entire single-use syringe  09  can be moved axially together with the attached cannula  05  inside the cannula protector  01 , and, by pressing the clamp elements  08 , it can be fixed in the given position. The sleeve  02  presents, between the base plate  03  and the projecting part  07 , at the other end, a sleeve length which is shorter than the length of the syringe plunger  11 . The bellows  06  is represented in the largely-compressed position, which can only be maintained if the user actuates the clamp elements  08 , and thus clamps the syringe in the sleeve  02 . In a representation which is different from the one chosen in  FIG. 2  to facilitate the understanding, the free end  15  of the bellows  06  abuts, during the actuation of the syringe, against a stop ring  20  of the syringe plunger  11 , so that the bellows is compressed when a force is exerted in the axial direction on the syringe plunger or the actuation plate  14  of the syringe plunger. The friction between the syringe cylinder  11  and the internal wall of the sleeve  02  is kept sufficiently small by providing enough clearance, so that the syringe can be moved substantially only against the resistance of the bellows into the sleeve  02 . 
     The compression length of the bellows  06 , by which the latter must be compressed at least, and by which it has to expand again after the removal of the compression force, corresponds at least to the length of the cannula  05  (possibly minus its foundation), to achieve a complete covering of the cannula during the expansion of the bellows and the associated movement of the sleeve  02 . 
     Before the injection proper, the user uncovers the cannula  05  by pushing the syringe into the sleeve  02 . The injection can then be positioned as usual. If the user puts down the syringe out of his/her hand, the clamping force disappears, the bellows  06  undergoes a release of tension, and in the process moves the sleeve  02  over the cannula  05 . 
     The syringe plunger  13 , in the state represented in  FIG. 2 , is moved far into the syringe cylinder  11 . This corresponds to the time during the injection or when the injection solution is sucked into the syringe. 
     In the embodiment represented in  FIG. 2 , the cannula protector  01 , together with the single-use syringe  09 , forms an advantageous single-use syringe system, which is fitted with the cannula  05 , and which can also be delivered in this completed form, filled with an injection solution. 
     The actuation plate  14  of the syringe plunger  13  presents, for the purpose of mechanical locking after use, two radially opposite engagement hooks  16 , which, after complete insertion of the syringe plunger  13  into the syringe cylinder  11 , engage in an engagement groove  17 . In the represented embodiment, the engagement groove  17  is arranged on the syringe cylinder  11  of the single-injection syringe  09 ; however, in a specially preferred embodiment, the engagement groove  17  can be arranged directly at the end of the bellows  06 , resulting in an advantageous undetachable connection between the single-use syringe  09  and the cannula protector  01  after use of the single-use syringe  09 . The function of the cannula protector is not affected by the engagement of the engagement hooks, so that, after completion of the injection, a locking of the single-use syringe as well as a covering of the used cannula is obtained. 
       FIG. 3  shows a spatial representation of the single-use syringe system according to  FIG. 2 . The cannula protector  01  presents axially running viewing slits  18 , preferably four distributed over the periphery, which allow the observation of a scale  19  of the single-use syringe  09 . The observation possibility is also necessary to be able, for example, to observe the flow of blood into the syringe. 
       FIG. 4  shows, in three views, the cannula protector  01  which is divided into two in the axial direction, and which can be assembled from two halves  21 . This embodiment is particularly cost-effective in its manufacture, because the injection molds can have a substantially simpler design. In the two-part design, the bellows  06  can have a shape without a coiled structure. 
     In Figures b) and c), the engagement mechanism for connecting the halves  21  is represented in detail. The two halves  21  present preferably each a nose  22  and a groove  23  at three axially distributed connection places. 
     A completely prepared respectively-filled single-injection syringe can be inserted advantageously into one of the halves, and encapsulated by snapping the second half shut. As a result, the handling is simplified. There are no special requirements in terms of the sealing properties of the cannula protector  01 , and therefore the two-part embodiment can be used preferably. 
       FIG. 5  shows a detail view of an engagement mechanism of a single-use syringe system similar to the one already described in  FIG. 2 . In addition to the already-described function, the bellows  06  presents a fixation section  24  which engages during assembly in the engagement groove  17  provided in the syringe cylinder  11  of the single-use syringe  09 . The engagement hook  16  of the syringe plunger  13 , after completion of the actuation, also engages in this engagement groove  17 , which reliably prevents repeated opening or use of the single-use syringe. 
       FIG. 6  shows a detail view of a preferred embodiment of a single-use syringe  09  to be used in the single-use syringe system. The syringe cylinder  11  presents, in its interior, close to the outlet which is provided with the nozzle  12 , a flange  26  which strikes a predetermined breaking edge  27 , which is provided on the syringe plunger  13  and which is narrowed in cross section, during the closing actuation of the single-use syringe  09 , destroying it in the process. As a result of the destruction of the predetermined breaking edge  27 , the syringe plunger  13  is no longer mounted with seal in the syringe cylinder  11 , and thus it is no longer possible to suck an injection solution again into the single-use syringe. 
     The combination of the described characteristics leads to a single-use syringe system which satisfies stringent hygiene requirements. The risk of damage to the cannula is minimized, because the cannula is protected by the cannula protector, as soon as the syringe is no longer held by the hand. At the same time, reuse is prevented.