Abstract:
A cannula is retractably mounted with a needle holder ( 9 ) in a housing ( 5 ). A switching device ( 7, 8 ) allows the hollow needle ( 10 ) to be retracted after use into the housing ( 5 ). The needle holder ( 9 ) secures against rotation the hollow needle ( 10 ) in the housing ( 5 ) in a predetermined orientation. The housing ( 5 ) is preferably provided on its outer side with markings ( 13 ) which indicate the orientation of the hollow needle ( 10 ). The hollow needle ( 9 ) cannot twist when it is retracted. Another advantage is that the orientation of the needle point need not be determined before making an injection.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a syringe with a hollow needle and a needle holder attached to the hollow needle whereby the needle holder is retractable within the syringe housing and the needle may be retracted with the help of a device into the syringe housing after its use. 
     2. Description of the Related Art 
     A syringe of this type has been made known by the state-of-the-art of U.S. Pat. No. 5,480,385. This syringe has the problem that during retraction of the hollow needle, injection solution may be released through the needle and this injection solution might be mixed with the patient&#39;s blood. 
     A similar syringe has been made known by the state-of-the-art of U.S. Pat. No. 5,114,404. This syringe has the particular disadvantage in that the needle holder, together with the hollow needle, is turned during its release. Parts of tissue may be set free within the patient&#39;s body by turning of the needle, which represents a considerable risk of injury. Furthermore, another syringe was made known by EP-A-0 290 176, which also makes retraction of the needle possible after use. However, this syringe has a problem in that the needle may be in an arbitrary position in relation to its longitudinal orientation. The position of the needle point in relation to the syringe housing is hereby arbitrary and must first be determined before each injection. Retraction of the needle is caused here by means of a pressure spring and there is also the danger that the needle rotates during retraction. Other similar syringes have been made known by WO 92/16 248 and WO 92/058 18. 
     BRIEF SUMMARY OF THE INVENTION 
     The above-mentioned disadvantages and problems are avoided by the use of the innovative syringe in that the needle is secured against rotation within the syringe housing in a predetermined position and whereby retraction of the needle in this position is conducted without turning the needle in at least in a portion of the needle path. The portion of the needle path during which the needle remains non-rotating is preferably the foremost portion of the retraction path. The stabilization against needle rotation within the syringe housing makes it possible, for example, to mount the needle always in a predetermined position in relation to a marking on the syringe housing. Since the position of the needle point may be easily seen in the syringe housing, inspection of the needle point is not necessary and injection is thereby made easier and is also safer. 
     According to the invention, means for volume compensation during retraction of the needle are located in the syringe housing of a typical syringe. These means are designed, for example, in such a manner that a partial vacuum is created before retraction. The fluid displaced during needle retraction then compensates for this low pressure. Thereby it can be prevented that during needle retraction, injection solution is released through the needle, which might be mixed with the patient&#39;s blood. 
     According to a preferred development of the invention, the means for volume compensation show a movable element placed within the syringe housing, which may be moved before needle retraction to create a partial vacuum. According to further development of the invention, this movable element is at the same time a trigger element by which retraction is caused. This makes a design possible that has very few separate components. 
     According to further development of the invention, the hollow needle may be moved longitudinally at the circumference and the rear section where it has a seal. Thereby the danger of air injection is prevented by a high degree. At the same time, problems may be avoided during drawing of the injection solution into the syringe and settling of air bubbles is prevented. Since only a seal around the circumference of the needle has to be created, the to-be-sealed area is relatively small and causes a relatively small amount of friction during needle retraction. Additionally, the guiding parts stabilize the needle. According to one version, the syringe is equipped with a Luer nozzle that makes the use of the syringe possible in conjunction with standard hypodermic needles. However, the syringe may also be attached rigidly to a barrel. 
     According to further development, triggering the retraction is possible at any time whenever the needle retraction is caused by actuating elements, which are located inside the syringe in a radial manner and which move against one another. These actuating elements are preferably attached to the syringe housing. Steady handling of the syringe is achieved by the counter movement of the actuating elements and thereby unnecessary movement of the syringe is avoided. 
     Additional advantageous characteristics are shown in the related patent claims and the following specifications and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One version of the invention is subsequently described in more detail by drawings. The following is shown: 
     FIG. 1 A longitudinal view of an innovative syringe in its basic position and a longitudinal view of a portion of a syringe barrel. 
     FIG. 2 A longitudinal view relating to FIG. 1, without a protective cap illustrating a retracted needle. 
     FIG. 3 A cross-sectional view along line Ill—Ill of FIG.  1 . 
     FIG. 4 A cross-sectional view along line IV—IV of FIG.  1 . 
     FIG. 5 A cross-sectional view along line V—V of FIG.  1 . 
     FIG. 6 A cross-sectional view along line VI—VI of FIG.  2 . 
     FIG. 7 A view of the innovative syringe without a protective cap. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The illustrated syringe  6  shown in FIG. 1 in its basic position is detachable and is connected to an only partially shown barrel  1 . The connection between the syringe  6  and the barrel  1  consists of a fitting  20  at the rear portion of the syringe housing  5  and a conical fitting  2  at the front portion of the barrel  1 . The connection surface between fitting  2  and  20  is conical and corresponding to the known Luer connections. Such connections are well known in medical syringes. The housing  5  may also be connected rigidly with the barrel  1  according to a version not illustrated here. 
     The syringe housing  5  consists of a rear housing section  22  and a front housing section  23 , which are joined together at a connection point  27  by ultrasonic welding. A detachable protective cap  12  is placed on the front portion of the housing  5 , which prevents touching of the needle and which also covers with its rear bell-shaped rim  35  two actuating elements  4  that retract the needle  10 . 
     The hollow needle  10  has the usual sharp point  17  and is firmly connected to the needle holder  9  at its middle portion by means of an adhesive section  34 . The needle holder  9  has at its rear section several outwardly pointing teeth  19 , which are resting correspondingly against inwardly pointing teeth  18  of a switching box  8 . The force of a pressure spring  11  applies tension on the needle holder  9  and against the above-mentioned teeth  18 . The needle  10  protrudes with its rear portion  36  into a longitudinal channel  25  of element  7  and is sealed at its outer movable side with an encircling sealing lip  24 . Element  7  functions as a trigger element as well as a volume-compensating device as described in more detail later on. Element  7  is guided by a shell-shaped fitting  28  at the rear housing section  22  and is sealed by an encircling sealing lip  29  and is also held in place in the shown position by an interlocking beaded rim  26 . 
     The needle holder  9  has at its front area  14  a ratchet-like cross section as shown in FIG. 4, and is guided by a corresponding guiding channel  15  in the syringe housing  5  to prevent turning. The needle holder  9  is placed into the guiding channel  15  in such a manner that the angular ground point  17  always remains in the same position in relation to the above-mentioned marking  13  in FIG.  7 . The position of the point  17  may thereby be seen by the marking  13  on the syringe housing. 
     The needle  10  and the needle holder  9  may be fully retracted into the syringe housing  5  after use of the syringe  6 . Retraction is caused by the release of tension of the pressure spring  11 . To trigger the retraction, the switching box  8  is rotated until the teeth  18  are located in an opening between the teeth  19  as shown in FIG.  6 . The needle holder  9  is thereby no longer blocked at the switching box  8  and is then moved to the rear by the pressure spring  11  into the position shown in FIG.  2 . The point  17  is hereby placed safely into a channel  38  of the housing  5 . It is essential that the retraction of the needle  10  is guided and turning is prevented at least during the first phase of retraction. The switching box  8  is turned when triggering the retraction, however, the needle holder  9  is not turned. The needle holder  9  is also kept from turning during retraction and during engagement into the guiding channel  15 . In addition, the needle  10  is supported during retraction within the channel  38  and is also supported by the sealing lip  24 . 
     The switching box  8  is a part of the switching mechanism  3  and rests movably against the projection  39  in the syringe housing  5 . To be able to turn, the switching box  8  has switching teeth  33  at its back side that engage into corresponding switching teeth  32  of element  7 . To actually turn the switching box  8 , element  7  is moved in the direction of the arrow  40  whereby the slanted engagement surface  41  of the teeth  32  come into contact with the angled engagement surface  42  of the teeth  33 . Turning of the element  7  is thereby prevented by wedge-shaped blocks  43  that protrude in a circle toward the outside. Element  7  is moved with an actuating device that has two opposing actuating elements  4 . These actuating elements  4  have each an actuating cam  21  that is elastically molded to an arm  45  in the forward housing section  23 . The actuating cam  21  is moved radial toward the inside to cause retraction triggering of the needle  10  and thereby a force is transferred onto the slanted engagement surface  16 , which in turn causes movement of element  7  in the direction of the arrow  40 . The protective cap  12  is naturally removed when operating the actuating element. Triggering of the retraction is not possible while the protective cap  12  is in place since the cams  21  can not be reached. When moving the element  7  in the direction of the arrow  40 , a volume compensating space  31  is created that causes low pressure inside the syringe housing  5 . Thereby it is prevented that existing fluid is pushed out of the needle point  17  during retraction of the needle  10 . Element  7  serves thereby as a trigger element and as a volume compensating mechanism. At the same time, element  7  serves to seal the needle  10  at its rear section  36  and also serves as a guide. 
     Functioning of the syringe  6  will be subsequently described in more detail. 
     The protective cap  12  is removed from the syringe housing  5  to fill the barrel  1  with fluid, specifically with medicine. The point  17  of the needle  10  is submerged into the prepared fluid and the not-illustrated common plunger of the barrel is actuated correspondingly, whereby the fluid flows through the needle  10  and through the sealed channel  25  within the barrel  1 . As commonly done during administration of an injection, air may be pushed out before an injection is given by briefly lifting the plunger. Thereby it is prevented that air bubbles are created and are eventually set free by a position change and are then injected. When the barrel  1  is filled with fluid, then the needle  10  is inserted in the usual manner whereby the marking  13  shows the position of the needle point  17 . The marking  13  shows in an aseptic manner the slanted part of the needle point  17 . The fluid is then injected in a common manner by lifting the plunger cylinder. After injection, the above-mentioned retraction of the needle  10  is hand triggered by firmly pressing the actuating element  4 . The needle  10  is thereby guided and moved into the position shown in FIG. 2, whereby an unintentional touching of the needle  10  is no longer possible. 
     The syringe  6  is shown here in conjunction with a barrel  1 . However, conceivable is also the use of the syringe  6  for withdrawal of blood, for example, or for in-vitro diagnostics. The removal of the syringe  6  may not be necessary during uses of such kind. All components, except for the needle  10  and the spring  11 , may be manufactured as plastic injection molded parts. The number of these parts is comparatively small and assembly is suited also for series production. The relatively small volume requirements are also of importance, so that there is essentially little difference between the innovative syringe  6  and the common syringe without needle retraction.