Abstract:
A medical injection device is provided which includes a shield system and a syringe. The shield system includes a housing, a shield telescopically received in the housing slidably coupled to the housing and a driver that pushes the syringe stopper to cause drug injection. The driver is equipped with sensing elements that automatically detect empty syringe. A spring resiliently urges the shield from a retracted position to an extended position shielding the needle. The syringe is coupled to the housing. The shield is positioned externally to the syringe and the driver. The shield includes flexible latches to keep its position relative to the housing during storage and use. The axial movement of the driver in respect to the syringe causes an automatic release of the spring by sensors when the syringe is empty, allowing the spring to move and lock the shield in the extended position after use.

Description:
FIELD OF THE INVENTION  
       [0001]     The field of the invention relates to syringe safety systems and in particular to syringe shield systems for protecting against needle sticks.  
       BRIEF DESCRIPTION OF THE RELATED ART  
       [0002]     Syringes are well known medical devices for administering medicaments, drugs and vaccines to patients. Prefilled syringes are generally considered as those which are filled with a selected dosage of medicament, drug or vaccine by a pharmaceutical manufacturer for distribution to the end user. They are generally comprised of a glass barrel which contains the medicament, drug or vaccine, and a stopper slidably mounted within the barrel. The distal end of the barrel includes a needle cannula or the like affixed thereto or a connector for a needle cannula assembly such as a Luer connector. The proximal end of the syringe includes an integral flange and is open to allow the insertion of a stopper and a plunger assembly. The plunger and stopper assembly allows the user to apply manual force to the plunger, causing the medicament, drug or vaccine to be delivered through the needle cannula or other piercing element. The healthcare worker or patient grips the flange and applies pressure to the plunger generally with the thumb.  
         [0003]     The use of a sharp-pointed piercing element entails several types of risks. As long as the syringe is not in use ifs content is protected by a sterility cover that also prevents accidental an needle prick. Once the needle is exposed there are risks of accidental needle prick after use when the needle is contaminated, of accidental needle prick in case the syringe was not properly disposed of, and a risk of accidental or deliberate re-use. To avoid such accidents, many prior art hypodermic syringes have included different safety shields. Some of these considered telescopic shielding over the syringe barrel, others consider unique glass barrels. Telescoped shields can be moved between a retracted position, where the needle is exposed for use, to an extended position where the needle is surrounded by the shield.  
         [0004]     U.S. Pat. No. 6,159,184 describes such a telescopic shield where the user is expected to identify the end of drug delivery and then use his second hand to manually push the shield until it locks to the holder. Sampson et al demonstrate this approach in a number of earlier patents such as U.S. Pat. No. 6,004,296, U.S. Pat. No. 4,425,120 and U.S. Pat. No. 4,573,976 also planned for a prefilled syringe.  
         [0005]     U.S. Pat. No. 4,923,447 by Morgan discloses a shield system for hypodermic syringes which is spring-actuated. The release of the spring and triggering of the safety feature depends on the users action.  
         [0006]     It is ordinarily desirable to lock the needle shields in the protected positions, and a number of prior art designs provide for such locking. Some systems, such as those disclosed in U.S. Pat. Nos. 5,201,708, 5,242,240 and U.S. Pat. No. 5,318,538 by Martin, are designed to allow the shields to be retracted from their locked, extended positions.  
         [0007]     Another approach is demonstrated in U.S. Pat. No. 6,613,022 by Doyle where the user unsnaps a preloaded spring by moving the driver close to it&#39;s end of delivery position. The user is also expected to release his gripping fingers to allow the telescoping shield, which is external to the holder in that case, to slide forward and lock.  
         [0008]     The safety shield could be activated by different means. In U.S. Pat. No. 6,613,022, the driver has to reach a certain position relative to the holder; in patent application 20030050607 by Gagnieux the user is expected to apply an increased pressure over the driver to do the same.  
       SUMMARY OF THE INVENTION  
       [0009]     According to the present invention there is provided an injection device comprising: 
        a housing having a proximate end and a distal end, the distal end having an opening therein;     a cartridge barrel within the housing, the cartridge barrel having proximate and distal ends;     a needle cannula fixed to the distal end of the cartridge barrel, or attachment means for fixing a needle cannula to the distal end;     a stopper within the cartridge barrel;     a driver coupled to the stopper;     a shield coupled to the housing and slidable between a retracted and an extended position;     shield driver means activateable to urge the shield from the withdrawn position to the extended position; and     sensor means moveable with said driver and in slidable contact with an exterior surface of said cartridge barrel or an interior surface of said housing, the sensor means arranged to detect an end profile of the barrel or housing and to trigger activation of the shield driver means upon detection.        
 
         [0018]     This invention relates to a safety shield system for a syringe, medical cartridge or the like and such a system as used in combination with an assembly capable of functioning as a syringe. In accordance with the preferred embodiment of the system, the user is able to use a prefilled syringe using a similar action to that used with simple prefilled syringes. The user is able to observe the drug, to purge air, to titrate the desired dose, to hold the syringe as he/she is trained, to penetrate the skin and inject. Shielding of the needle will occur automatically without any further step required from the user. The shielding will be synchronized with the reaching of the end of delivery or the emptying of the cartridge.  
         [0019]     In accordance with the objects of the invention, a medical device is provided which includes an automatically operable shield system mounted to a syringe barrel. The system includes a tubular housing which defines an assembly enclosure. A tubular needle shield is slidably attached to the housing and preferably is telescopically received within the housing. The syringe barrel is received within the housing and shield assembly, partially within the tubular shield. The shield is extendable from a retracted position and encloses the needle cannula following the end of injection.  
         [0020]     In the disclosed embodiment, the shield includes a stop member adjacent its proximal end and the housing includes a stop member adjacent its distal end which releaseably retains the shield in its retracted position. In the preferred embodiment, the stop members on the shield comprise two latches adjacent to slits in the housing. The stop members prevent the shield moving forward before the end of delivery is achieved. The strength of that connection should be sufficient to withstand the shield&#39;s weight and effects of impact only. There is no force applied on the stopping members. The force required by the spring to disengage the shield from the housing is minimal.  
         [0021]     A compressed spring is trapped on the driver assembly. During injection the driver is moved forward by the user in order to push the drug from the glass barrel into the users tissue. The shield is releaseably retained in the housing. The spring is released from the driver and biases the shield axially toward the extended position following injection. Upon application of a force by the spring, the shield is released from the retracted position and covers the needle.  
         [0022]     The driver includes a central plunger acting like a conventional rod and two side arms acting as sensing elements. The sensing elements are the deflectable arms trapping the spring. The sensing arms act like a cam, which under the spring&#39;s load, senses the syringe&#39;s external profile. When the cams reach the distal side of the barrel the arms deflect and the spring is released from the driver. The spring bypasses the driver, impacts the shield, and releases the latches. Once the shield is released the spring drives it to the extended position where it is locked.  
         [0023]     The proximal end of the housing is preferably adapted to engage and retain the syringe flange upon receipt of the syringe barrel through the proximal end of the housing. Once the syringe is snapped to the housing it will remain stationary with respect to it.  
         [0024]     Prefilled syringes are sometimes used to aspirate drug, for example to mix a second drug into a filled cartridge. For that purpose it is important to have an axial connection between the driver and the syringe stopper. The axial attachment is achieved by having either a snap or a thread; a female part in the rubber stopper and a matching male part on the distal end of the driver plunger. The disclosed embodiment shows a snap connection between the plunger and the stopper yet, as will be further explained, a threaded connection is applicable too.  
         [0025]     When compared to other known techniques the current invention is unique by being the closest to regular manual injection. Therefore it is expected that it will take a shortest training for the user to get comfortable with using the system. The described embodiment does not require any additional actions from the user and is automatically triggered by the internal conditions of the system. The activation of the automatic safety feature is affected by a minimal chain of dimensions and is involving only a single part in addition to the syringe. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  is an isometric view of a preferred embodiment according to the invention;  
         [0027]      FIG. 1A  defines the planes of the device cross sections as A-A, B-B, and C-C, where A-A is the cross section through the driver side arms providing the observation window perspective, B-B is a cross section through a plane of the discard latches and C-C is a cross-section through a plane of the discard stoppers;  
         [0028]      FIG. 2  is an external view of the device from the observation window perspective in a storage position;  
         [0029]      FIG. 3  is an external view of the device in a plane perpendicular to the plane in  FIG. 2  in a storage position;  
         [0030]      FIG. 4  is a view as in  FIG. 2  with the device in a discard position;  
         [0031]      FIG. 5  is a view as in  FIG. 3  with the device in a discard position;  
         [0032]      FIG. 6  is a cross-section view of the device in plane A-A per  FIG. 1A  when in a storage position;  
         [0033]      FIG. 7  is a cross-section view of the device in B-B plane per  FIG. 1A  when in a storage position;  
         [0034]      FIG. 8  is a cross-section view of the device in C-C plane per  FIG. 1A  when in a storage position;  
         [0035]      FIG. 9  is a close-up view of the cross section of the syringe flange and housing interface;  
         [0036]      FIG. 10  is a cross-section view of  FIG. 6  after delivery and before removal from injection site;  
         [0037]      FIG. 11  is a cross-section of  FIG. 7  after delivery and before removal from injection site;  
         [0038]      FIG. 12  is a cross-section of  FIG. 6  with the device in the discard position after the removal from the injection site;  
         [0039]      FIG. 13  is a cross-section of  FIG. 7  with the device in the discard position after the removal from the injection site;  
         [0040]      FIG. 14  is a cross-section of  FIG. 8  with the device in the discard position after the removal from the injection site;  
         [0041]      FIG. 15  Housing isometric view;  
         [0042]      FIG. 16  Driver isometric view;  
         [0043]      FIG. 17  Shield isometric view;  
         [0044]      FIG. 18  Shield isometric view facing window;  
         [0045]      FIG. 19  Prefilled cartridge cross-section; and  
         [0046]      FIG. 20  Safety syringe exploded view. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0047]     A safety system is applied on a glass or plastic pre-filled syringe to protect users from any accidental needle prick after injection and/or to prevent reuse of a single use device. The accompanying figures clearly illustrate the three molded plastic parts which combine to form an embodiment and the pre-filled cartridge sub-assembly.  
         [0048]     The following description considers three main stages in the use of the preferred embodiment: the storage condition of the assembled system; the end of delivery before removing the injection device from the tissue; and the system after removal from the injection site with the needle automatically shielded and secured.  
         [0049]     The operation of the device described in the preferred embodiment follows the conventional way of using a simple standard pre-filled syringe. The syringe assembly (including prefilled syringe) is packaged to protect its content. Once the syringe is taken out of the packaging it is necessary to follow the manufacturers instruction: check the drug and its labeling, and identify the specific device details. In order to make that possible the safety device is fabricated using transparent polymers such as acrylic, polycarbonate or polystyrene. The selected materials do not require sterilization. The user should be able to purge the air bubble, titrate the required dose by using the syringe scale as it is currently done when using similar marketed products. In some specific cases the user will need to aspirate additional drug or diluent. The embodiment should consider this need by enabling a stopper motion in both proximate and distal directions through a reliable connection between the plunger and the stopper. The above activities will occur after the needle cover assembly is removed. The safety features should make it possible for the user to interact with the system in same way as with simple pre-filled syringes.  
         [0050]     The injection process follows all commonly known methodology. The device should create minimal interference in any type of eye contact with the device that the user might need. There will be a certain increase in the typical device diameter since additional barriers are added to the cartridge. However that increase does not make any difference in the way of use.  
         [0051]     Unlike other applications described in the background for this invention, this invention does not require any additional actions from the user. Injection process proceeds as usual. Once the end of injection is reached the shielding system is automatically triggered, providing the user a tactile indication of end of delivery in addition to the usual visual indication. As the user is removing the device from the injection site the shield is moved by a spring in the distal direction covering the needle. The shield is locked to the housing. The ejection of the shield by a spring does not require any increase in the force applied by the user for injection. The device needle is secured with the device ready for safe discard.  
         [0052]     An basic operation principle used in the described embodiment is a sensing elements sliding over the external side of the cartridge and sensing the end of the barrel while automatically triggering the shielding system.  
         [0053]     FIGS.  1  to  3  show different views of an embodiment of the invention in an initial unused state. These and other figures do not reflect the transparency of the plastic components. The safety syringe has a housing  100 , a shield  200  and a driver  300 . The spring  400  is positioned inside the assembly. It is important to position the spring where it will not interfere with viewing the scale and/or the drug. An observation window  110  (or a clear housing) is exposing the cartridge scale  502  and the drug  560 . The user holds the housing  100  at the finger grips area  112  and applies force, usually by the thumb, over  352  part of the driver  300 . The needle cover assembly  570  is removed prior to use. The needle cover assembly  570  exposed to the user is either a rigid plastic part  550  enclosing the elastomer sterility cover  540  or is the elastomer sterility cover  540  itself.  
         [0054]      FIG. 4  and  FIG. 5  illustrates the device following use, and in particular following the activation of the shield. The shield discard stopper  212  has moved from the top of the guiding track  106  in  FIG. 2  to the bottom of same track in  FIG. 4  preventing further distal motion of the shield. Furthermore the discard latch has deflected outward and prevents the reverse motion of the shield  200  as illustrated in  FIG. 4  and  FIG. 5 . The discard latch is initially positioned at the top of the guiding track  105 .  
         [0055]      FIG. 6  through  FIG. 14  show cross section views of the device describing 3 positions from 3 different perspectives. The A-A plane is parallel to the observation window  110  allowing a clear view of the driver  300  in different operation steps.  FIGS. 6, 10  and  12  are all cross-sections in plane A-A. Cross section B-B is in a plane of the discard latch  210 , allowing a clear view of latch  210  in slit  105  at different operation steps.  FIGS. 7, 11  and  13  are all cross-sections in plane B-B. Cross section C-C is in a plane of stopper  212 , allowing a clear view of the stopper  212  in slit  106  in different operation steps.  FIG. 8  and  14  are cross-sections in C-C plane.  
         [0056]      FIG. 6 ,  FIG. 7  and  FIG. 8  illustrate different cross-section perspectives of the embodiment before use. The driver is unable to move to the distal side of the barrel since the cannula  530  is occluded by  540 . The movement of the driver to the proximal side is also prevented by same means.  
         [0057]      FIG. 9  is a close-up view showing flange  520  engaged to the housing  100  by snaps  111 . Snaps  111  are preventing axial movement of the cartridge while housing slits  114  engaged with arms  320  prevent the driver rotational movement. Cartridge  500  is snapped to the housing by  111  and is supported in the radial plane by cams  340  pressed against the barrel  501  by the reaction of the spring  400 . The removal of the sterility cover assembly  570  could be accomplished by pulling on  570 . The cartridge is supported by the housing flange  116  when the needle cover assembly  570  is removed.  
         [0058]     The use of the device starts with the removal of the needle cover assembly  570 . After the air purge, titration and other steps are completed, the user starts the injection process by holding the device by the housing finger grip area  112  with two fingers and a thumb on the base/knob  350 . The needle is inserted in a conventional way. Then the driver is pushed by the thumb while the safety syringe is held by two other fingers. The driver  300  moves forward while carrying the preloaded spring  400 . With the exception of the axial displacement of the driver and stopper there are no changes in the relative positioning of other components in this embodiment.  
         [0059]     End of delivery is detailed in  FIG. 10  and  FIG. 11 .  FIG. 10  shows the driver after cams  340  have run off the end of the barrel  503 . The distal arm  322  of the driver  300  deflects under the spring  400  force to its molded state. Spring  400  will continue to slide along the cam cone  342  until it bypasses it. The proximal side of the spring is still pushing back the driver over spring support  323  while its distal side applies a force on the surface  205  of the shield flange  204 . The user is not expected to perform any additional steps outside actions related to the common injection techniques. That spring impact additionally provides to the user both a tactile and audible indication of the end of delivery signaling time to remove the device from the injection site.  
         [0060]      FIGS. 12, 13  and  14  show the preferred embodiment after the syringe assembly has been removed from the injection site and is ready for disposal. Under the axial force of spring  400  the shield  200  moves to the distal side and becomes locked. The forward motion of the shield  200  allows latches  210  to deflect out until these engage the distal edge  102  of the housing  100 . During the forward motion of the shield  200 , the spring proximal end is supported by spring support  323  of the driver  300 . A potential reverse motion of the driver  300  is prevented by the support provided by cams  340  on the end  503  of the barrel  501 . Stopper  212  ( FIG. 8  and  14 ) slides in slits  106  from its proximal end until the distal side, and prevents the removal of the shield  200  from the device. Injection is completed with the device secured for disposal.  
         [0061]     After the device is used and the shield ejected by the spring, reuse is highly difficult to perform due to the position of spring  400  acting as a supporting cylinder inside tubular body  203 .  
         [0062]     Individual component description:  
         [0063]     The housing  100  is shown in  FIG. 15 . The housing  100  has a tubular section  103  and a flange  116  on its proximal side  101 . The distal side  112  of the flange  116  is used for finger gripping. Different shapes of the gripping area could be used in the preferred safety syringe embodiment.  
         [0064]     The proximal flange surface  113  of the housing flange  116  has locking elements  111  to permanently attach the cartridge flanges  520  (the cartridge is described in  FIG. 19 ) to the housing  100  during assembly. Snaps  111  are dimensioned to capture the wider side of the cartridge flange. The cartridge  500  is stationary with respect to the housing during use.  
         [0065]     The housing  100  has also three sets of longitudinal openings in its cylindrical section  103  including an observation window  110  on both sides of  103 , a discard latch guiding track  105  and a stopper guiding track  106 . Tracks  105  and  106  could be arranged across the diameter of  103 . The tracks  105  and  106  and the observation windows  110  are coaxial with the axis of the housing. The side walls of  110 ,  105  and  106  could be parallel as illustrated in  FIG. 15  to simplify the part manufacturing by injection molding. Furthermore, the observation window  110  is optional for clear plastic materials.  
         [0066]     Flange  113  has a central opening with a diameter  115 . The diameter  115  is above the external diameter of the spring  400  yet it is smaller than the diameter of the cartridge flange  520 . Snaps  111  are arranged to lock the cartridge on its larger side  520  adjacent to the proximal surface of  113  of the housing flange  116 . Flange  116  has two slits  114  to accommodate the driver side arms.  
         [0067]     Driver  300  is detailed in  FIG. 16 . Driver  300  has a plunger  305  similar to a conventional syringe plunger. At the end of the plunger  305  is a knob  345  with a grove  344  and a plate  312  to capture the stopper. Alternatively the knob  345  could have a thread for connecting to the stopper of the cartridge.  
         [0068]     On its proximal side the driver  300  has a base  350  acting as a conventional push pull knob. The base  350  also functions as a bridging element with the plunger  305  and side arms  320  attached to it. Each side arm  320  has a front arm section  322  and a rear arm section  321 . The middle point where  321  turns into  322  has a protrusion  330 . The protrusion  330  contacts and slides on the surface of the cartridge barrel.  
         [0069]     The front arm section  322  is designed to trap and retain a preloaded spring while the device is in storage. The proximal end of the spring rests on a spring support  323 . The distal end of the spring releasably rests on a cam cone  342 . The distal end of the front arm section  322  further has a cam  340  resting on the cartridge barrel and a front taper  343  to assist in the assembly.  342  is able to allow the bypassing of the spring after end of delivery is sensed. The cam  340  follows the external shape of the cartridge and acts as the system sensor. Front arm  322  could have a reduced thickness  335  on its proximal end performing the function of an axis.  
         [0070]     Shield  200  is detailed in  FIG. 17  and  FIG. 18 . The shield  200  has a tubular body  203 . The shield  200  has a proximal end  201  and a distal end  202 . It also has a flange  204  on the distal end  202  of the tubular body  203 . The external diameter of  203  is in a sliding relationship with the inner diameter of the tubular section  103  of the housing. The flange  204  has a needle opening  206  with a diameter big enough to allow the removal of the needle cover assembly  570 . The proximal side  205  of the flange  204  is flat while its external side  207  of the flange  204  could be shaped like a cone for better needle visibility. Tubular section  203  could have two openings  213  positioned across the diameter and matching housing windows  110  to create the safety syringe observation window. The longitudinal slits  214  act as the driver side arm guiding tracks. Undercuts  215  are introduced to assist in the molding of discard latches  210 . Discard latches  210  provide two functions: first to keep the shield in its axial location before shielding and second to prevent the exposure of the needle after use. Though no forces are applied to the shield it is essential to maintain its position before shielding. The distal side of the latch  211  interacts with the housing slit  105  to prevent any displacement unless an axial force is applied when shielding is triggered.  
         [0071]     The second function of the latch is to prevent the exposure of the needle after use. The discard latch  210  is shaped to make it relatively flexible for radial deflection yet highly rigid while axial force is applied. After shield  200  is moved to its shielded position the latch  210  leans on the housing  102  and prevents the shield from traveling back. Shield  200  also includes stoppers  212  to prevent any relative shield to housing rotational move and to prevent further axial move or disassembly of the shield.  
         [0072]     Shield  200  is designed for injection molding. In particular the side walls of  210  and  212  could be parallel to the observation window  213  side walls. Features  213 ,  210  and  212  are design to match  110 ,  105  and  106 . Flange  204  includes several local slits  216  on its inner side. These are intended to minimize the bulk of the shield.  
         [0073]     Cartridge assembly  500  is detailed in  FIG. 19 . Cartridge assembly includes the barrel  501  usually made of glass, a needle  530  attached to is distal end, and a flange  520  on its proximal end. The barrel  501  contains drug  560  retained in the barrel  501  by a stopper  510 . The stopper is also used to push the drug through the cannula  530 . The cannula  530  is covered by an elastomer sterility cover  540 . The elastomer cover could be also covered by a plastic sterility cover  550 . The  530  and  540  form a sterility cover assembly  570 . The described components are common in conventional cartridges. The preferred embodiment in the invention is designed to integrate the standard components without any changes. Barrel  501  is sometimes covered by a laminate with a printed scale  502 . Barrel  501  is a tube like part having a constant external diameter with the distal end  503  diameter decreasing towards the cannula. Spring  400  is a conventional coiled spring.  
         [0074]     Assembly process description.  
         [0075]     The safety syringe assembly process takes place in a clean environment with the filled cartridges reaching the final assembly as closed components with a sterile content. Additional aspect related to selection of materials will be discussed below.  
         [0076]     One option of the assembly process is detailed below. An exploded view of the embodiment is shown in  FIG. 20 . The assembly starts with connecting the driver  300  to the cartridge  500  by either snapping or threading the element  345  to stopper  530 . The position of the driver  300  relative to the flange  520  of the cartridge  500  should be controlled for a cartridge with a threaded stopper. A limited unthreading might be required for proper orientation of parts. Next step is the positioning of spring  400  on the front arm section  322 . Spring  400  is placed on the driver and cartridge assembly by applying an axial force. Front taper  343  on the distal end of  320  supports the engagement with the spring. The spring  400  could be slightly deformed by a radial force to an oval shape to assist in the assembly.  
         [0077]     Cartridge  500 , driver  300  and preloaded spring  400  form a subassembly. This subassembly is inserted into proximal opening  115  of the housing  100 . The rotational position it dictated by slits  114  guiding side arms  320 . Spring  400  external diameter is smaller than the opening  115 . The subassembly is moved forward until cartridge flange  520  is connected by snaps  111  to the housing  100 . The connection is now permanent, no relative move, axial or rotational between holder  100  and cartridge  500  is possible.  
         [0078]     Final assembly step involves shield  200 . Slits  214  are positioned to be engaged with arms  320 . The external diameter of  203  fits to slide in the internal diameter of  103 . The internal diameter of  203  is bigger than the external diameter of the spring  400 . The shield  200  is inserted into the assembly from the distal end until the discard stopper  212  will contact the distal edge  102  of the housing  100 . The proximal edge of  212  is tapered. An axial force applied to the shield  200  will deflect sections of the tubular body  203  separated by the cam guiding tracks  214 . These will return to return to its original position once stoppers  212  will reach slits  106 . This step completes the assembly.  
         [0079]     Whilst the invention has been described above with reference to an injection device where the needle insertion and injection steps are carried out manually, the invention is also applicable to auto-injectors where one or both of these steps is carried our automatically. In particular, the shield driver means may additionally provide a driving force for said driver, with the coil spring being fixed at its proximal end to the housing, and the spring release mechanism fixing the spring to the driver at its distal end.