Patent Publication Number: US-2017354791-A1

Title: Safe auto-needle device

Description:
FIELD OF THE INVENTION 
     The invention relates generally to medical syringe devices, and more specifically to a device for auto-injection such as is performed by a laymen. 
     BACKGROUND 
     Patients with a chronic illness may require repeated injection of medicaments to treat their condition, and may prefer to administer their own injections, to maximize convenience. 
     Typical errors made by laymen attempting to perform self-injection, include: triggering a premature discharge of the drug prior to insertion of the needle, accidental needle pricks, unintentional distortion of the needle prior to use, and breakage of the syringe by inadvertently dropping a glass syringe. 
     Safe needles are relatively simple syringes, which protect a user from unintentional needle pricks by either removing or sheathing the needle after use. While many safe needles, or more costly auto-injectors, provide protection from accidental needle pricks, the need exists to protect a layman from the remaining errors listed hereinabove. While auto-injectors usually prevent most laymen errors, they are relatively expensive for the end user or the pharmaceutical companies. Auto-injectors may be preloaded for a single use, requiring extensive refrigerated storage space. They typically come with a fixed injection speed which may be painful for the user. They are often complex in structure, requiring many user steps and thus are difficult to use. When they are non-disposable and accept prefilled syringes, they require an initial pricey acquisition expense. 
     State-of-the-art injection solutions currently available for use by both healthcare professionals and laymen, include standard needles and syringes, and safety needles such as U.S. 2010/0016803. These are typically attachable through a luer/luer-lock connector to standard luer syringes and safety syringes, preferably to prefilled glass/plastic syringes with staked needles, such as U.S. Pat. No. 6,685,676, or disposable and reusable “pens” and auto-injectors such as U.S. Pat. No. 8,376,998 (disposable, single-use) and WO 2014/037946 (reusable, electronic). None of these overcome the aforementioned disadvantages. 
     The safe auto-needle of the present invention provides the novel advantage of allowing the user to control the injection speed, providing increased compliance and comfort. This feature is not known in prior art disposable auto-injectors. The invention also offers the major advantages of an auto-injector, namely, the needle is hidden in all stages of operation and automatically penetrates the skin upon pressing the device against the injection site, thus reducing patient anxiety and perceived pain, and enabling consistent and appropriate needle penetration depth. After use, the needle is automatically locked in a covered position to prevent needle-stick injuries. 
     The auto-needle of the invention is characteristically disposable, and is relatively inexpensive for the end-user to purchase. 
     It is the object of the present invention to provide a layman with an auto-needle which is simple to use and protects the user from typical layman errors such as premature discharge of the medication, breakage of the syringe or bending of the needle prior to use. These and other features and advantages of the invention will be enlarged upon in the detailed description of the invention that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the invention, with regard to the embodiments described, reference is made to the accompanying drawings, in which components are not necessarily drawn to scale, and in which: 
         FIGS. 1-33  describe five embodiments of the invention: 
         FIG. 1-8  relate to a basic Embodiment 1; 
         FIG. 9-16  describe Embodiment 2, having an interlock for preventing a user from pressing the plunger before the needle has completely penetrated the injection site. Additionally, a tri-component plunger is included that allows syringe movement for needle penetration without movement of the proximal plunger. 
         FIGS. 17-24  describe Embodiment 3, having an alternative two-component ratcheting NS remover. 
         FIGS. 25-32  describe Embodiment 4, comprising an alternative interlock design, to prevent pressing the plunger before complete needle penetration has occurred. Additionally, a plunger one-way ratchet system prevents additional movement of the plunger after use. 
         FIG. 33  describes Embodiment 5, in which the plunger is locked from moving, both prior to use of the device, and after use, to prevent spillage of a hazardous medicament. 
     
    
    
     SUMMARY 
     There is thus provided a safe auto-needle device for injection, comprising:
         a) a main housing;   b) a syringe-support for receiving a proximal end of a disposable prefilled syringe; the disposable prefilled syringe comprises: a piston; a proximal end including a flange; and a distal end terminating in a needle; the needle covered by a needle sheath (NS);   c) a drive mechanism for advancing the syringe-support distally towards an injection site;   d) a generally tubular needle shield concentric to the main housing; the needle shield moveable from a first position wherein the needle is covered, to a second position in which the needle is at least partially exposed, to a third fully extended position in which the needle is irreversibly concealed;
           the generally tubular needle shield comprising a distal end for contacting an injection site, and a proximal end;   
           e) a spring urging distal movement of the needle shield; and the needle shield comprising a spring seat;   f) a needle sheath (NS) remover, designed to mate with and irreversibly grip the needle sheath (NS), for removal of the needle sheath prior to injection;   g) a locking mechanism for preventing premature advancement of the needle; wherein the locking mechanism is constructed such that depressing upon the distal end of the generally tubular needle shield, results in release of the locking mechanism; and the tubular needle shield cannot be depressed prior to removal of the needle sheath (NS);   h) a plunger rod for engaging the piston of the prefilled syringe, wherein the speed of depressing of the plunger is manually controllable by a user;
           wherein in use of the device, the NS remover is grasped and removed; the distal end of the needle shield is brought into contact with and pressed upon an injection site, resulting in release of the locking mechanism, and in drive of the syringe-support and the associated syringe, distally until needle penetration; and upon depressing of the plunger, a medicament may be injected.   
               

     In certain embodiments, the drive mechanism (c) comprises a compressed spring and a spring seat, for urging the syringe-support distally towards the injection site. 
     Optionally, the plunger rod comprises at least one locking tab to prevent pulling of the plunger rod in the proximal direction, instead of pressing of the plunger rod. 
     In such case, a rear cap may be included, having a hollow center through which the plunger rod enters, and an internal lock bracket, the lock bracket interacting with the locking tab of the plunger to prevent pulling of the plunger, ensuring unidirectional movement of the plunger. 
     Moreover, the locking mechanism (g) may comprise T-shaped locking arms of the main housing, opposing and pressing on the syringe-support; and release of the locking mechanism comprises lifting of the T-shaped locking arms radially outwards, by proximal movement of the needle shield. 
     Additionally, a locking mechanism may be included for locking the needle shield after injection, in the third fully extended position, fully covering a needle tip. The needle shield locking mechanism may comprise: lower locking arms present upon the main housing, which hold the needle shield in a fully extended position covering the needle, after use. 
     Furthermore, a terminal distal end of the NS remover may comprise bumpers to receive and dampen axial load applied to the NS remover when the device is dropped; thereby preventing breakage of a prefilled syringe. 
     In certain embodiments, the NS remover is comprised of an inner tubular portion comprising snap teeth for mating with an NS, and an outer concentric tubular portion comprising a grip face; and flexible connection arms connect the inner and outer portions. 
     The device may comprise a transparent viewing window in the main housing, allowing viewing of the state of a medicament present in a prefilled syringe held in the device. 
     In a presently preferred embodiment, the device comprises an interlock, for preventing depressing of a plunger, prior to advancement of the syringe-support to a needle penetration location. In such case, the interlock may comprise an outwardly facing locking face. Further, movement of the interlock, and premature pressing of the plunger, are prevented during storage, by engagement of locking face protrusions located upon anterior plunger pusher, within appropriate grooves of locking faces of a rear cap; and the outwardly facing locking face of the interlock prevents the locking face protrusions from bending inwardly. Additionally, release of the interlock can be performed by distal movement of the syringe-support, by the drive mechanism; resulting in distal movement of the interlock&#39;s locking face from its previous position opposite the locking face protrusions of the anterior plunger pusher; the protrusions are free to bend inwardly and disengage from the internal grooved locking faces of the rear cap; allowing the anterior plunger pusher to be pressed by a user. 
     In some embodiments, the plunger rod is a tri-component plunger having one-way ratchet teeth. The tri-component plunger may comprise: an anterior plunger pusher; and a proximal plunger having angled one-way ratchet teeth, which may engage appropriate one-way ratchet teeth upon a distal plunger; and the proximal plunger comprises in an internal face a storage area in which the ratchet teeth are disengaged prior to use of the device, the storage area allowing movement of the distal plunger due to internal air pressure in a syringe. In some instances, the tri-component plunger, advantageously does not prevent movement of the syringe-support for needle penetration, when a user forcefully grasps the anterior plunger pusher during use. 
     The invention additionally provides a NS remover comprised of: 
     an internal part for mating with the NS; 
     and an external part for transferring impact forces upon dropping of the device, to a stopper on the main housing; 
     and ratchet teeth are present on one of: the internal part, and the external part; for engaging flexible teeth upon the other of: the external part and internal part; the ratchet teeth allowing tolerance in position of the NS during storage. 
     The NS remover internal part may be guided axially on the needle shield thus preventing a bending load on the needle. 
     In some embodiments of the device, the locking mechanism (g) comprises locking arms present on the syringe-support; the locking arms entering stop windows on the main housing; and wherein in release of the locking mechanism, activation slopes located at the terminal end of the locking arms slide against activation slopes of the proximally moving needle shield; thereby bending the locking arms inward and removing the locking arms from the stop windows. 
     Moreover, the interlock may be structured to block pressing of the plunger until the syringe-support has advanced distally to a needle penetration position; thus preventing user error of premature discharge of a medicament. 
     Optionally, the plunger comprises a plurality of locking teeth present upon the length of the plunger; 
     and the interlock comprises a pivot hinge, and a flexible load beam for urging pivoting of the interlock on the hinge upon user initiation of an injection; 
     and the interlock terminates in at least one locking tooth designed to engage one or more of the locking teeth present upon the plunger, the engagement preventing the plunger from being pressed; and the engagement occurring prior to needle penetration. 
     In some instances, the interlock locking tooth is designed to engage the at least one plunger locking tooth, after use of the device. 
     Furthermore, the interlock may comprise one or more guiding holes designed to mate with and accept therein, one or more lengthened release fingers present upon the syringe-support; the mating preventing the at least one locking tooth of the interlock from disengaging from the locking teeth of the plunger; wherein distal advancement of the syringe-support towards an injection site results in removal of the one or more lengthened release fingers from within the one or more guiding holes. 
     In some instances, the device includes a plunger one-way ratchet system for preventing pulling of the plunger proximally and allowing only pressing of a plunger distally. In such case, optionally the plunger is a two component plunger comprised of a proximal plunger component and a distal plunger component; each of the plunger components having at least one ratchet tooth allowing mating of the two plunger components during pressing of a plunger; and the plunger components have a pre-engagement positioning, allowing the components to slide upon one another allowing for tolerance in axial positioning, prior to pressing of the plunger. 
     Optionally, the interlock is additionally structured to block movement the plunger after use of the device. In such case, the interlock comprises two terminal locking teeth angled in opposing directions and engaging appropriately angled locking teeth, present upon the length of the plunger. 
     Further, the device may comprise a plurality of longitudinal ribs located internally within the needle shield, the ribs providing axial support for the prefilled syringe. 
     In one embodiment, the main housing includes a viewing window allowing viewing of the contents of the prefilled syringe when the tubular needle shield is in the first position. 
     The invention also provides an NS remover, for use with an injection device comprising a syringe, a needle and a needle sheath; the NS remover comprising: 
     an internal part for mating with the needle sheath (NS); 
     and an external part for transferring impact forces upon dropping of the injection device, to a stopper on a main housing of the injection device; 
     and ratchet teeth are present on one of the internal part and the external part, for engaging flexible teeth upon the other of the external part and the internal part; the ratchet teeth allowing tolerance in position of the (NS) needle sheath during storage. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. There is no intention to limit the invention to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. 
     In a general overview, the safe auto-needle of the invention is a cost-effective disposable device, into which disposable prefilled syringes are placed. The device provides several novel safety advantages, especially important for a layman user. Premature discharge of the contents of the syringe is prevented, as occasionally a user will attempt to press the syringe plunger before the needle has been fully deployed. Similarly, a mechanism is included to prevent the plunger from being extended instead of being depressed, to avoid unintentional medication spillage or introduction of air bubbles into the syringe. Prefilled syringes typically are marketed including a soft or rigid needle sheath (NS), which needs to be forcefully removed by the user prior to use, leading to accidental distortion of the needle tip, and dropping and breakage of glass syringes. The auto-needle of the invention includes a component termed the NS Remover, which allows effortless gripping of the needle sheath, prevents the user from bending the needle when removing the sheath, and is structured to provide shock absorbance in case the device is dropped. Additionally, the needle is shielded, until triggered by the user to advance to its pre-penetration position, and is once again automatically shielded after use, to prevent post-injection inadvertent pricks. In addition, the auto-needle of the invention allows the user to control the injection speed, providing reduced injection-related pain, similarly to simple hypodermic syringes (while maintaining the advantages of auto-injectors such as prevention of needle pricks, hiding the needle, and automatic needle penetration, thus reducing patient anxiety and perceived pain). The invention provides a solution for patients that prefer to control the injection speed, and may suffer from needle-phobia, allowing them to persist with their prescribed treatment. 
     In contrast, prior art simple safe needles do not provide these numerous safety features, while auto-injectors are costly and merely provide patient control of medication injection speed. 
     Referring now to  FIG. 1 , the components of the Safe Auto-Needle  10  are shown in both an isometric-exploded view. 
     Referring to the isometric view, the Safe Auto-Needle  10  of the invention, also termed the “SAN-P”, includes a plunger rod  290  at its proximal end, a main housing  210 , an outer cover  230  and an NS remover  240  which allows quick and proper removal of a needle sheath prior to use. 
     Referring to the exploded view in  FIG. 1 , plunger rod  290  includes one way locking and piston elements, to prevent pulling (hyperextension) of the plunger proximally, instead of compression of the plunger, described hereinbelow in relation to  FIG. 1F  and  FIG. 2B . 
     A disposable prefilled syringe  100  containing a medicament is inserted by a pharmaceutical company or by a user into the auto-needle device  10  of the invention. Prefilled syringe  100  typically comprises a syringe barrel  140  including a flange  120 , a piston (not shown), and a Needle Sheath “NS”  110  which conceals a needle tip (not shown). 
     The disposable prefilled syringe  100  is received and supported radially by a needle shield  220  and an upper syringe-support  260 . Needle shield  220  slides upon the main housing  210  proximally while pressed against the injection site, when needle penetration is triggered by the user. Syringe spring  270  is compressed during assembly, and acts to urge the prefilled syringe  100  and the syringe-support  260  distally towards the injection site. 
     In the embodiment shown, needle shield  220  and the needle shield front  225  make up a needle shield assembly, and are joined together by any method (bonding, welding, snaps, etc.). The needle shield assembly can be produced as one integral part or produced from any number of parts and assembled thereof. Needle shield spring  250  urges the needle shield  220  distally. 
     NS remover  240  engages the NS preferably by a snap fit, and allows easy removal of the NS (Needle sheath) to ready the device for injection. The NS remover  240  preferably covers the needle shield front  225 . 
     A rear cap  280  is also included to interact with the plunger rod  290  and syringe spring  270  and ensure unidirectional movement of the plunger rod  290 , as described hereinbelow in relation to  FIGS. 1E, 2B and 7 . 
     Referring now to  FIG. 1A , the main housing  210  is shown in isometric view, in side view and in cross-section view, taken along section line AP-AP in side view. 
     Referring to  FIG. 1A , isometric view, T-shaped locking arms  212  press upon the syringe-support  260  (shown enlarged in  FIG. 1D ) which holds the prefilled syringe  100 ; thus locking arms  212  prevent prefilled syringe  100  from prematurely advancing distally before the injection process is initiated. 
     Syringe stop  215  of main housing  210  is described in relation to  FIGS. 6A and 6B , as stopping movement of syringe-support  260  and syringe  100  in the needle penetration state. 
     Lower locking arms  211  are described in relation to  FIG. 8  as interacting with the needle shield  220  (via ribs  228  of needle shield) after injection is complete, to hold needle shield in final fully extended position and prevent needle sticks during handling after use. 
     Referring now to  FIG. 1B , needle shield  220  comprises rearward facing arms  229  which terminate in rib distal sides  221   d  and proximal facing tapers  221   p.  These elements ( 229 ,  221   d ) interact with the syringe-support  260  (not shown) to prevent premature distal movement of the needle shield (described in  FIG. 2A ). Additionally, during needle penetration, the rearward facing arms  229  and proximal facing tapers  221   p  force release of T-shaped locking arms  212  of the main housing (described in  FIG. 4A ). 
     In addition, needle shield  220  preferably comprises a generally tubular body portion  227  and spring seat  222  against which the needle shield spring  250  abuts (spring not shown). 
     Note rib  228  of needle shield  220  (best shown in isometric view at far right, and in side view bottom center) which acts to distally limit movement of needle shield  220  in fully extended position after use. 
     Referring now to  FIG. 1C , an NS remover  240  is illustrated, which allows easy removal of the NS (Needle Sheath) to ready the device for injection. 
     Note (in isometric views), snap teeth  241  formed in the inner portion  245  of the NS remover  240 . When a prefilled syringe (not shown) is inserted into the device, the snap teeth  241  engage with and irreversibly hold the proximal rigid rim  112  of the NS (shown in  FIG. 1G, 3A ). The NS remover  240  allows a user to grip and apply sufficient force to remove the NS, without distorting the needle. 
     Bumpers  243  can receive and dampen any axial load or shock applied on them, when the device is accidentally dropped, as bumpers  243  are located on the most distal (prominent) end of the device. The axial load or shock is transmitted to the flexible connection arms  242  which dampen the axial load or shock and thus limit the force transmitted to the inner portion  245  of the NS remover  240 . This dampening reduces chances of breakage of the syringe barrel  140  and/or its flange  120 , in cases the syringe barrel is made of glass (shown in  FIG. 1G ). 
     Note that any number of flexible connection arms  242  can be provided, in any shape that will provide flexible axial positioning between inner portion  245  and the gripping face  244  which is an outer area of the NS Remover  240 . 
     Axial stoppers  246  are one or more protrusions, which prevent distal disengagement of the NS  110  from the NS remover  240  following removal of the NS remover. It can be understood that such axial stoppers can be produced by protrusions as shown, ribs, or any other shape. 
     Referring now to  FIG. 1D , syringe-support  260  receives and supports the proximal end of the prefilled syringe  100 . The barrel of the prefilled syringe  100  is inserted into the central lumen of the support, and the flange of the syringe (shown as  120  in  FIG. 1G ) is supported distally and radially by the syringe seat  262 . 
     Protrusion  261  interacts with the needle shield  220  to prevent the needle shield  220  from prematurely advancing distally and prematurely triggering a needle prick. This is enlarged upon below in relation to  FIG. 2A . 
     Referring to the upper left view of  FIG. 1D , syringe-support edge  263  plays a role in controlling the extent of penetration of the needle to the outermost limit where needle penetration is considered complete, as described in relation to  FIG. 6A . 
     Referring to  FIG. 1E , rear cap  280  is shown. Rear cap  280  has a hollow center through which the plunger rod enters. 
     Lock bracket  281  of the rear cap interacts with a front locking segment on the plunger rod ( 291  in  FIG. 1F ), to prevent a user from pulling and hyper-extending the plunger instead of pressing it. (Described in relation to  FIG. 2B ). 
     Referring now to  FIG. 1F , the plunger rod  290  includes a forward facing tip  292  which engages a piston of prefilled syringe  100  (not shown). A plunger back end  294  needs to be pressed by a user to advance the piston and inject medication present in the prefilled syringe  100 . 
     A front locking segment  291  is a tab which prevents a user from pulling and hyper-extending the plunger instead of pressing it, as such action will thrust the front locking segment  291  against the lock bracket  281  of the rear cap  280 , stopping hyper-extension of the plunger  290 . The front locking segment  291  is flexible to allow it to pass through the syringe barrel  140  during injection. 
     An additional tab, termed the rear locking segment  293 , similarly prevents extension of the plunger by a user (as the plunger should only be pressed and not extended). The rear locking segment  293  flexibly passes through the lock bracket  281  of the rear cap  280  when the plunger  290  is pressed. 
     It can be understood that any number of locking segments (such as  291  and  293 ) can be provided. Additional locking segments along the plunger rod  290  can provide additional stops for preventing residual fluid spill out of the syringe barrel  140  if the piston is disengaged from the barrel. Alternatively, the plunger rod  290  can be produced without any such locking elements, or with only one of them. 
     Referring to  FIG. 1G , a prefilled syringe  100  is shown, comprising a syringe barrel  140  which includes a flange  120 , a piston  130 , a needle  106  with a needle tip  105 , and a rigid needle sheath (NS)  110  which conceals the needle tip  105 . The NS  110  can be a rigid or a soft needle sheath. 
     Note the proximal rigid rim  112  of the NS which engages irreversibly with the snap teeth  241  of the NS remover (not shown), allowing removal of the NS prior to use of the device. 
     Referring to  FIGS. 2A and 2B , the Safe Auto-Needle (SAN-P) of the invention is shown, in its fully assembled storage state. 
     The syringe spring  270  is supported on the rear cap  280  and distally on the flange  120  of the prefilled syringe  100 . 
     In another embodiment (not shown), there are one or more elements which separate between the distal side of syringe spring  270  and flange  120 . 
     The NS remover  240  preferably covers the needle shield front  225 , and is engaged to the NS  110  which conceals the needle  106  including the needle tip  105  of the prefilled syringe  100 . The NS remover  240  also prevents access to the needle shield  220 , and thus prevents accidental pressing on the needle shield and its movement in the proximal direction, which would result in premature needle penetration. 
     The outer cover  230  is mounted on the main housing  210 , and is fixed by any method of bonding, welding, one or more snaps, etc. Outer cover  230  is preferably made of transparent or clear material, but it may be formed with one or more viewing through windows to allow viewing of the contents of the prefilled syringe  100 . Alternatively, outer cover  230  can be made of an opaque material, e.g., in cases where there is no need to view the contents of the prefilled syringe  100 . 
     In  FIG. 2B , enlargement BB, the snap teeth  241  of the NS remover  240  have engaged with and grip the proximal rigid rim  112  of the NS  110 , to allow effortless removal of the NS using the NS remover  240 . 
     The NS remover bumpers  243  of NS remover  240  receive potential axial load or shock applied on it, this dampening reduces chances for breakage of the syringe barrel  140  and/or its flange  120 . The syringe spring  270  provides additional damping further reducing chances for breakage of the syringe barrel  140  and/or it&#39;s flange  120 . 
     The plunger rod  290  is engaged with the piston  130  at its forward facing tip  292 . This engagement can be of any form, such as a screw as shown, as a snap-fit, or any other suitable form. 
     Referring to  FIG. 2B , enlargement BC, unidirectional movement of plunger  290  in correct orientation is ensured, as follows: plunger rod front locking segment  291  prevents the piston  130  from being pulled out from prefilled syringe  100 , by colliding with plunger rod lock bracket  281  of rear cap  280 . The plunger rod front locking segment  291  is flexible to allow it to pass through the syringe barrel  140  during injection. 
     The syringe spring  270  urges the prefilled syringe  100  and the syringe-support  260  distally. The flange  120  of syringe barrel  140  of prefilled syringe  100  is supported distally and radially on the syringe seat  262  of syringe-support  260 . 
     Referring back to  FIG. 2A , cross-sectional View B-B, the needle shield spring  250  is supported proximally on the spring seat  214  of main housing  210 . The needle shield spring  250  urges the needle shield  220  distally by pushing on the needle shield spring seat  222 . 
     Referring to Enlargement B- 3 , rib distal sides  221   d,  and proximal facing tapers  221   p,  of needle shield  220  interact with protrusion  261  of the syringe-support  260  to prevent premature distal movement of the needle shield  220 . 
     The T-shaped lock arms  212  of the main housing  210  oppose the syringe-support  260  which holds the prefilled syringe  100 , thus preventing syringe from prematurely advancing distally. 
     As best seen in  FIG. 2B , Cross-Sectional View BA-BA, the NS remover  240  is shown in the device, after the snap teeth  241  have engaged with the NS  110 . A user may now utilize the NS remover  240  to effortlessly remove the NS; the NS remover  240  assures that the needle tip (not shown) will not be bent by the forces applied. 
     Additionally, gripping face  244  is an outer area of the NS remover. An axial load applied by the user on the NS remover gripping face  244  in the direction shown by arrow  1000 , will remove the NS  110 , as the NS remover snap teeth  241  have engaged with and grasp the NS distal rigid rim  112  of the NS  110 . 
     One or more NS remover snap teeth  241  may be provided. 
     In order to protect the Needle  106  from damage, during removal of the NS remover  240  and the NS  110 , the inner portion  245  of the NS remover  240  is guided axially within the needle shield  210  (best seen in cross sectional views B-B in  FIG. 2A  and BA-BA in  FIG. 2B ), thus preventing any bending load on the needle  106 . 
     Referring to  FIG. 3A , the device  10  is shown after removal of the NS. No additional changes have occurred in the positioning of other components of the device  10 . 
     The needle  106  remains essentially hidden throughout this stage. 
     The NS remover  240  includes one or more protrusions termed “axial stoppers”  246 , which prevent distal disengagement of the NS  110  from the NS remover  240  following removal. It can be understood that such axial stoppers can be protrusions as shown, ribs, or may have any other shape. 
     Referring to  FIG. 3B , an isometric view of the device  10  is shown, after removal of the NS. Outer cover  230  has been removed from this view to allow view of inner components. 
     In Enlargement AK, the T-shaped locking arms  212  of the main housing  210  are pressed upon front facing surfaces  264  of the syringe-support  260 , prevent prefilled syringe  100  from prematurely advancing distally before the injection process is initiated. 
     The Viewing window  223  of needle shield  220  and the viewing window  219  of the main housing  210  are shown, which together with a transparent/clear outer cover  230  (not shown) allow a user to view the medicament prior to injection, to ensure unfavorable changes in the drug appearance have not occurred (such as sedimentation or cloudiness) which could indicate decomposition of the drug. 
     Referring now to  FIGS. 4A and 4B , a user now triggers the beginning of the injection process, by pressing the distal end of the device  10  upon an exposed injection site (shown pressed only half-way). 
     In the left illustration of  FIG. 4A , when the needle shield distal end  226  is pressed in the direction indicated by arrow  1050 , against the injection site  5000 , this forces the needle shield  220  to move proximally indicated by arrow  1100 , thus triggering exposure of the needle tip. 
     Release of the needle shield  220  occurs as follows: 
     In  FIG. 4A , Central Drawing D-D and Enlargement A- 3 , pressure upon the injection site compresses the needle shield spring  250 , urging the needle shield  220  proximally in direction  1100 . This movement then results in the proximal facing tapers  221   p  of the rearward facing arms  229  of the needle shield  220 , contacting the inner side of the T-shaped locking arms  212  of the main housing  210 . This lifts the T-shaped locking arms  212  radially outwardly towards directions  1200 . 
     Note in Enlargement A- 3  the position of proximal facing tapers  221   p  relative to T-shaped locking arms  212 . Proximal facing tapers  221   p  has moved proximally towards the terminal end  212   p  of T-shaped locking arms. Proximal facing tapers  221   p  allows T-shaped locking arms  212  to slide upon the slope of proximal facing tapers  221   p  with minimal friction, and T-shaped locking arms are lifted outwards. 
     In comparison, refer back to  FIG. 2A , Enlargement B- 3 , to see initial storage position of rib distal side  221   d  compared to T-shaped locking arms  212 . Rib distal side  221   d  is considerably more distally located than in  FIG. 4A . 
     Referring to  FIG. 4B , an isometric view is shown of this stage (initial triggering), shown without outer cover  230  and without the injection site. 
     In Enlargement AK of  FIG. 4B , note positioning of proximal facing tapers  221   p  relative to T-shaped locking arms  212 . Proximal facing tapers  221   p  has moved proximally towards the T-branch of terminal end  212   p.  During proximal movement of the proximal facing tapers  221   p  they contact T-shaped locking arms  212  and lift them radially outwardly. 
     Referring now to  FIG. 5A , needle shield  220  has moved proximally to the full extent, lifting of T-shaped locking arms  212  outwardly, releasing the syringe-support  260 , to allow movement of the syringe-support  260  which will result in needle penetration. (Needle has not yet penetrated at this stage). 
     Note in Enlargement A- 3 , the T-shaped locking arms  212  are now illustrated generally parallel to the longitudinal axis of the SAN-P  10  after they have been lifted. 
     In Cross Sectional View E-E, the needle shield spring seat  222  of the needle shield  220  acts as hard stop against the front edge  218  of the main housing  210  preventing the needle shield  220  from moving further proximally. 
     Referring to  FIG. 5B , the SAN-P device  10  is shown in an isometric view; without the outer cover  230  and without the injection site  5000 . Needle has not yet penetrated at this stage. 
     Note in Enlargement AK of  FIG. 5B , the maximally proximal position of proximal facing tapers  221   p  of needle shield  220 , relative to T-shaped locking arms  212 . 
     Referring now to  FIG. 6A , needle penetration is shown, resulting from rapid distal movement of syringe-support  260  together with the prefilled syringe  100 . 
     The syringe-support  260  was urged towards the injection site by the syringe spring  270 . 
     In Enlargement A- 3 , the syringe-support  260  progressed distally until its movement is stopped when the syringe-support edge  263  of syringe-support  260  abuts the syringe stop  215  of the main housing  210 . 
     At this stage, the needle tip  105  of the prefilled syringe  100  has penetrated into the appropriate depth at the injection site  5000 . 
     Referring to  FIG. 6B , the device  10  is shown in isometric view after needle penetration, (without cover  230 , and without injection site). 
     Referring to  FIG. 7 , after needle penetration, the user now presses the plunger to inject the medication. 
     The rate of injection may be manually controlled by the user, who controls the force he applies when pressing the plunger. This avoids the pain associated with too rapid injection, especially known to occur with too rapid injection of viscous materials, or of medicaments having lipid delivery vehicles. 
     In upper two drawings of  FIG. 7 , the user has pressed the plunger rod flange  294  maximally, and the plunger rod  290  has moved distally as indicated by arrow  1300 . This advances the piston  130  maximally, which injects the fluid medicament via needle tip  105 . 
     Referring to Cross-Section G 1 -G 1  (lowest on  FIG. 7 ), the front locking segment  291  of plunger rod  290 , has flexibly bent inwardly upon its entry into the syringe barrel  140 . 
     At the end of the injection, the piston  130  will reach the end of the syringe barrel  140  and stop, thus indicating to the user that the injection is complete. 
     Referring still to Cross-Section G 1 -G 1 , the rear locking segment  293  of plunger rod  290 , has flexibly passed through the lock bracket  281  of the rear cap  280 . 
     In this location, the rear locking segment  293  opposes the lock bracket  281 , thus preventing a user from extending back the plunger rod  290  through the rear cap  280  in the proximal direction (which would result in drawing fluid from the injection site, back into the syringe). 
     Any number of locking segments  291  and  293  can be provided, or locking segments can be eliminated. Additional locking segments along the plunger rod  290  can provide additional backward stops for preventing residual fluid spill out of the syringe barrel if the piston  130  is disengaged from the syringe barrel  140 . 
     Furthermore, to eliminate such potential spill out of residual fluid that may be toxic, a plunger rod lock can be added, and can be activated depending on the relative position of the plunger rod to the needle shield, the prefilled syringe, the housing or any other part. 
     Referring to  FIG. 8 , injection has been completed and the device is shown in its “discard” state after removal of the SAN-P device  10  from the injection site. In this state, inadvertent needle pricks are prevented during handling for discard, since the needle shield is locked in its fully extended state, hiding the needle tip. 
     Referring to Cross-Section H-H of  FIG. 8 , removing the SAN-P device  10  from the injection site results in the needle shield  220  automatically moving distally relative to the main housing  210 , urged by the expansion of needle shield spring  250 . The distal movement of the needle shield  220  is stopped/limited by rib  228  of the needle shield  220  contacting stopper  216  of main housing  210 . 
     Referring to Cross-Section H 1 -H 1  of  FIG. 8 , another section is shown illustrating the components that lock the device in its needle-shielded position, for discard. 
     Upon distal movement of the needle shield  220  (which occurred when the device was removed from the injection site), rib  228  of the needle shield  220 , forces the lower locking arms  211  of the main housing  210  to bend outwardly, thus allowing rib  228  to pass the distal face  217  of the lower locking arms  211 . 
     At this stage, the distal face  217  limits and prevents proximal movement of the needle shield  220 , so that the needle tip  105  is covered and protected by the needle shield  220 . 
     In this state, reuse and inadvertent needle-sticks cannot occur from a used needle. 
     Referring to  FIGS. 9-16 , another embodiment of the invention is described, having additional safety features to prevent a user from pressing the plunger and discharging the medicine before the needle has completely penetrated the injection site. An “interlock” element ensures this. Furthermore, a tri-component plunger is included that allows syringe movement for needle penetration without movement of the proximal plunger. Additionally, the tri-component plunger allows the user to start injection of the medication immediately after the needle insertion, without any “idle stroke” (floating movement) between the plunger components. Moreover, this tri-component plunger allows variable positioning of the piston relative to the SAN-P assembly, due to variable positioning of the piston in the syringe caused by drug filling tolerances. Slight movement of the piston that may occur in response to changes in ambient pressure and temperature during storage, and, due to SAN-P components assembly tolerances. 
     Referring to  FIG. 9 , an exploded view is shown of Embodiment Two, having these additional safety features. Most of the central components are similar to those described hereinabove in relation to  FIGS. 1-8 . Novel aspects will now be described: 
     Rear cap  480  comprises grooves which end at locking faces  481  (enlarged in  FIG. 10D ), which engage with terminal fingers  612  of anterior plunger pusher  610  (best shown in  FIG. 10F ), and together with interlock  500 , prevent premature pressing of the plunger pusher  610 . 
     Plunger rod  290  previously described, has been replaced with anterior plunger pusher  610 , proximal plunger  620  and distal plunger  630 . To ensure above mentioned functionality of the plunger assembly and relative movement of the plunger components, unique one way ratchet teeth  632  may be seen on the end of distal plunger  630 ; these engage with ratchet teeth  622  on the proximal plunger  620  (best shown in  FIGS. 10H and 10G ; engagement and ratcheting described in  FIG. 14 ). 
     Interlock  500  blocks pressing of the tri-component plunger ( 610 , 620 , 630 ) prematurely (before the needle had been deployed). 
     Syringe-support  460  is lengthened, including connection arms  461  which interact with the interlock  500  and with the anterior plunger pusher  610  (described in relation to  FIG. 11B  and more specifically detailed section view B 11 . 1 -B 11 . 1  of  FIG. 11B ). 
     Referring still to  FIG. 9 , other central components of the SAN-P device  20 , which remain essentially unchanged from the previous Embodiment (described in  FIGS. 1-8 ), are shown: prefilled syringe  100 , (previously shown in  FIG. 1G ), a main housing  410 , a needle shield  420 , an outer cover  430 , an NS remover  240 , (as previously shown as  240  in  FIG. 1C ), a needle shield spring  450 , and a syringe spring  470 . 
     Referring now to  FIGS. 10A-10H , enlargements of the central components of the invention are presented, as follows: 
       FIG. 10A  illustrates the main housing  410 . Locking arms  412  of the main housing have replaced the T-shaped locking arms  212  described in the previous embodiment ( FIGS. 1-8 ). The generally tubular rearward portion of the main housing  410  is longer than the generally tubular rearward portion of the main housing  210 . 
       FIG. 10B  illustrates the needle shield  420 . Note rearward facing arms  429  including bridge  421 . 
       FIG. 10C  illustrates the syringe-support  460 . Protrusions  468  which extend from the beam  467  of the syringe-support  460 , hold the distal side of bridge  421  of rearward facing arms  429  of the needle shield  420  (previously shown in  FIG. 10B ), preventing distal movement the needle shield  420  during storage (interaction shown in Enlargement  11   a.   2 ). 
     Referring still to  FIG. 10C , protrusions  466 , and ribs  462  are shown. The protrusions  466  support and limit distal movement of the interlock  500  until the injection procedure is triggered by a user. 
       FIG. 10D  illustrates the rear cap  480 , which includes internal grooves ending with locking faces  481 . 
       FIG. 10E  illustrates the interlock  500 , which includes an outwardly facing locking face  510 , strut  520 , and distal ring  505  and proximal ring  507 . 
       FIG. 10F  illustrates the anterior plunger pusher  610 , which is the most proximal component of the tri-component plunger. Terminal fingers  612  are shown, having locking face protrusions  611  extending there-from. 
       FIG. 10G  illustrates the proximal plunger  620 , the middle component of the tri-component plunger. The internal surface of flexible arms  625 , defines angled ratchet teeth  622 ; angle is best seen in upper illustration. Ratchet teeth  622  are instrumental in guaranteeing one-way movement of the plunger (pressing of the plunger and not extension of the plunger), once they have engaged with corresponding ratchet teeth  632  of the distal plunger  630  (shown in  FIG. 10H ). 
     Note area between reference numerals  623  and  624 . When ratchet teeth  632  of distal plunger (not shown) are present in this area, they are disengaged from ratchet teeth  622 , allowing slight movement relative to one another, of the plunger components proximal plunger  620  and distal plunger  630 . This slight movement may occur due to changes in ambient pressure and temperature during storage, which affects the amount of air present in the prefilled syringe, resulting in mild movement of the syringe piston  130 . Point  623  is therefore defined as minimum air point  623 , and point  624  is therefore defined as maximum air point  624  (reflecting the volume of air present at a given time within the prefilled syringe, and the relative position to which the distal plunger ratchet teeth will move according to this internal air pressure). 
     Ring  621  of the proximal plunger  620  snap-fits with the anterior plunger pusher  610  (via slot  617 , not shown). 
       FIG. 10H  illustrates the distal plunger  630 , which is the third component of the tri-component plunger. Note outwardly facing angled ratchet teeth  632 . 
     Distal Tip  633  connects to the syringe piston  130  (shown in  FIG. 11A ). 
     Referring now to  FIG. 11A and 11B , the SAN-P device  20  is shown in the storage position. 
     Referring now to  FIG. 11A , and Enlargement  11   a,  the snap teeth  241  of the NS remover  240  have engaged with and grip the proximal rigid rim  112  of the NS  110  of the prefilled syringe  100 . 
     The NS remover bumpers  243  receive potential axial load or shock when accidentally applied, as described herein above. Syringe spring  470  provides additional damping, further eliminating breakage of the syringe  100 . 
     The syringe spring  470  is supported proximally on the distal face  482  of rear cap  480 . The syringe spring  470  urges the syringe-support  460  distally by pushing on the spring seat  465  of the syringe-support  460 . 
     In Enlargement  11  a. 2  (central enlargement), the locking arms  412  of the main housing  410  hold step  464  of the syringe-support  460 , thus preventing the syringe-support  460  and the prefilled syringe  100  from moving distally. 
     In same Enlargement, the distal side of bridge  421  of rearward facing arms  429  of the needle shield  420  holds the needle shield  420  on the proximal side of protrusion  468  which extends from beam  467  of the syringe-support  460 , thus bracing the needle shield  420  and preventing it from moving distally during storage. 
     Referring  FIG. 11A , cross-sectional  figure A11 -A 11  and enlargement  11   a,  the needle shield spring  450  is supported proximally on the spring seat  414  of main housing  410 . The needle shield spring  450  urges the needle shield  420  distally by pushing on the needle shield spring face  422 . 
     The outer cover  430  is mounted on the main housing  410  and fixed by any method of bonding, welding, one or more snaps, etc. 
     Referring to Enlargement A 11 . 1 -A 11 . 1  (top), the discard arms  411  of the main housing  410  may be manufactured straight, or with mild arch as shown in  FIG. 10A  and can become deformed during assembly by engaging of the extension  413  of the discard arms  411  of the main housing  410  with the inner face of the outer cover  430  as shown in  FIG. 11A . Alternatively, the discard arms  411  of the main housing  410  can be manufactured already in the shape as shown in Enlargement A 11 . 1 -A 11 . 1  of  FIG. 11A . 
     As best seen in sectional view A 11 . 2 -A 11 . 2 , flange  120  and the syringe barrel  140  of prefilled syringe  100  are supported axially on syringe seat  469  of syringe-support  460  and radially on the syringe-support  460 . 
     Referring now to  FIG. 11B , the storage position of the distal plunger  630  and proximal plunger  620  is shown. 
     In Enlargement  11   b.   1 , though distal plunger  630  is located within arms  625  of proximal plunger  620 , the ratchet teeth  632  are situated within “storage positioning range” (between points  623  and  624 ). Thus ratchet teeth  632  have not engaged their counterpart ratchet teeth  622  of proximal plunger  620 . This allows distal plunger to move distally or proximally within the limits of the ““storage positioning range” area. Axial movement of the syringe piston  130  may occur due to tolerances or change in axial position of the syringe piston  130  at this stage as described above. 
     The syringe piston  130  axial position in the prefilled syringe  100  may depend on tolerances in positioning during filling process of the prefilled syringe  100 , and on movement of the syringe piston  130  due to changes in ambient pressure and temperature. The syringe piston  130  axial position within the SAN-P device  20  depends also on assembly tolerances of the prefilled syringe  100  within the SAN-P device  20 . 
     Referring to central cross-section B 11 -B 11 , the distal tip  633  of the distal plunger  630  is connected by any method of bonding, welding, threading, one or more snaps, etc. to the syringe piston  130 . 
     Anterior plunger pusher  610  and proximal plunger  620  are fixedly connected by snap-fit formed by slot  617  of plunger pusher  610  and ring  621  of proximal plunger  620 . This connection can be formed in any way such as gluing, other way of snap-fit, ultrasonic welding or even forming the plunger pusher  610  and proximal plunger  620  as one unitary part. 
     In Enlargement B 11 . 1 -B 11 . 1 , the locking face protrusions  611  of anterior plunger pusher  610  are engaged within the grooves of locking faces  481  of rear cap  480  thus preventing the distal movement of the plunger pusher  610 . 
     Protrusions  466  extending from of the lengthened connection arms  461  of the syringe-support  460  prevent the interlock  500  from moving distally. 
     The distal face of ribs  462  of the connection arms  461  of the syringe-support  460  and the distal ring  505  of the interlock  500  are positioned with an axial gap between them (see “GAP” in enlargement B 11 . 1 -B 11 . 1 ). The outwardly facing locking face  510  of the interlock  500  therefore prevents locking face protrusions  611  of the plunger pusher  610  to bend inwardly, thus preventing the anterior plunger pusher  610  from axially moving distally due to premature pressing of the plunger pusher  610 . 
     In Enlargement B 11 . 2 -B 11 . 2 , the rim  615  of anterior plunger pusher  610  is limited from moving in the proximal direction by the distal face  482  of rear cap  480 . Thus any attempt by the user to pull the plunger pusher  610  proximally and disengage the anterior plunger pusher  610  is prevented. 
     Referring to  FIG. 12 , the user has removed the NS remover  240  along with the attached NS  110 , by pulling in direction  1000 . No additional changes have occurred in the positioning of other components of the device  20 . 
     Referring now to  FIG. 13 , a user now triggers the beginning of the injection process, by pressing the distal end of the SAN-P device  20  upon an exposed injection site  5000 , in the distal direction  2000 . The needle shield distal end  426  is forced to move proximally in direction  2500  relative to the main housing  410 . This figure shows the device immediately prior to movement of the prefilled syringe  100  and the syringe-support  460  distally. 
     In Enlargement  13 . 1 , bridge  421  of rearward facing arms  429  of the needle shield  420 , has moved proximally, thus forcing the locking arms  412  of the main housing  410  to lift radially outwardly. 
     In cross-sectional Enlargement  13 . 2 - 13 . 2 , when locking arms  412  bend outwardly, they release the step  464  of the syringe-support  460 , allowing syringe-support  460  to move distally together with prefilled syringe  100  due to force applied by the syringe spring  470  (shown in cross-sectional view A 13 -A 13 , where it is shown enlarged compared to upper view from which the cross-section is taken). This results in needle penetration into the injection site, as described in relation to  FIG. 14 . 
     Anterior plunger pusher  610  extends from the proximal end. Should a user grasp it forcefully and continuously during use, this will not prevent the desired movement of the syringe-support  460  and needle penetration. This is an advantage of the tri-component plunger (anterior plunger pusher  610 , proximal plunger  620  and distal plunger  630 ). 
     Referring to  FIG. 14 , needle tip  105  has fully penetrated into the injection site  5000 . Note cross-sectional view A 14 -A 14  is shown enlarged compared to upper view from which the cross-section is taken. 
     The syringe-support  460  has been urged by the syringe spring  470  to fully advance distally until the syringe-support edge  463  of the syringe-support  460  is stopped, by abutting upon the syringe stop  415  of the main housing  410 . 
     In this position, the needle tip  105  of the prefilled syringe  100  has penetrated to the appropriate depth into the injection site  5000 . 
     The distal plunger  630 , which is connected to the syringe piston  130 , has moved along with the prefilled syringe  100 . 
     Referring to Enlarged Partial Section  14 . 1 - 14 . 1 , this distal movement results in engagement of ratchet teeth  632  of the distal plunger  630 , with the counterpart ratchet teeth  622  of the proximal plunger  620 . This engagement is achieved by outwardly deflecting the flexible arms  625  of proximal plunger  620  on which the proximal plunger ratchet teeth  622  are formed. The axial position of the engagement between the distal plunger ratchet teeth  632  and the proximal plunger ratchet teeth  622  depends, inter-alia, on the initial axial position of the syringe piston  130 . 
     In Enlarged Partial Section  14 . 2 - 14 . 2 , the interlock  500  has moved distally and no longer prevents a user from pressing the plunger and discharging the medication: 
     The interlock  500  has been pushed distally in direction  4400  by the distal face of ribs  462  of the connection arms  461  of the syringe-support  460 . 
     Distal movement of the interlock  500  has removed the interlock&#39;s locking face  510  from its previous position and is no longer opposing terminal fingers  612  of the anterior plunger pusher  610  to bend inwardly and disengage the internal grooved locking faces  481  of the rear cap  480 . Anterior plunger pusher  610  may then be pressed by a user. 
     Referring to  FIG. 15 , medication has been injected by a user, who has pressed the anterior plunger pusher  610 , at the user&#39;s preferred injection rate. Note cross-sectional view A 15 -A 15  is shown enlarged compared to upper view from which the cross-section is taken. 
     When the anterior plunger pusher  610  is pressed in the distal direction  4700 , it urges all three of the tri-component plunger components to move distally (proximal plunger  620 , distal plunger  630 , and anterior plunger pusher  610 ). Distal movement only occurs, due to the engagement of the ratchet teeth  622  of proximal plunger  620  and ratchet teeth  632  of distal plunger  630 . The syringe piston  130  of the prefilled syringe  100  is thus moved distally to inject the fluid via the needle tip  105 . 
     Injection ends when the syringe piston  130  has reached the end of the syringe barrel  140  and stops, indicating that the injection is complete. 
     Referring to  FIG. 16 , the device  20  is shown in the discard position. In this state, inadvertent needle pricks are prevented during handling for discard, since the needle shield is locked in its fully extended state, hiding the needle tip. Note cross-sectional view A 16 -A 16  is shown enlarged compared to upper view from which the cross-section is taken. 
     After removing the SAN-P device  20  from the injection site  5000 , the needle shield  420  is urged by needle shield spring  450  to move distally relative to the main housing  410 , to its maximally extended state. 
     Referring to Enlargement  16 . 1  (center), the needle shield  420  is then locked in this maximally extended position, as follows: Rib  428  of the needle shield  420 , has forced the needle shield locking arms  411  to bend outwardly thus allowing the rib  428  to pass the locking arms  411  of the main housing  410 , and reach the stop position shown in enlargement  16 . 1 . In this stop position, rib  428  is blocked by locking arm  411  from moving proximally. 
     Referring to Enlarged Partial Section B 16 -B 16 , distal axial movement of needle shield  420  is stopped by the distal facing edge  423  of the needle shield  420  which reaches the needle shield stop  416  of the main housing  410 . 
     In this state, reuse and inadvertent needle-sticks cannot occur from a used needle. 
     Referring now to  FIGS. 17-24 , a third embodiment of the device is described, having an 
     NS remover of another design. The terminal external end of the NS remover is attached to the main housing, and if the device is dropped, transfers forces to a stopper on the main housing, to prevent breakage of the syringe, in another manner than described in other embodiments. NS remover is comprised of an external part which attaches to the main housing, and an internal part which grasps the NS. 
     Referring to  FIG. 17 , an exploded view is shown of Embodiment Three of the device  30 , including (left to right): NS remover external part  340 , NS remover internal part  343 , needle shield  320 , needle shield spring  350 , main housing  310 , syringe spring  370 , prefilled syringe  100 , syringe-support  360 , rear cap  380 , and plunger rod  390 . 
     Sticker  330  is stuck upon on the main housing  310 . The sticker  330  can be made of transparent material, opaque, or partially opaque, and may have a viewing window for viewing the appearance of the medication. The SAN-P assembly  30  can be also produced without sticker  330  or with another external component preferably made of plastic, alternatively to sticker  330 . 
     Referring now to  FIGS. 18A-18F , enlargements of the central components of the invention are presented, as follows: 
       FIG. 18A  illustrates the main housing  310 . Main housing  310  is formed with cutouts  312  which engage protrusions  321   d  of the needle shield  320  to lock the needle shield  320  in its extended position at discard orientation. 
     Stop window  315   p  (best shown in perspective view at top) engages the syringe-support  360  and prevents its movement during storage. 
     Stopper  316   a  are circumferential ribs which absorbs impact forces transferred to it by the external part  340  of the NS remover, should the device  30  be dropped accidentally. 
     Snaps  311  are used to hold the needle shield  320  during the assembly process of the SAN-P  30 , but have no role during the operation of the device. 
     In perspective view at top and cross-section views C-C and D-D, several internal slots  316   b  receive guiding ribs  324  of the needle shield  320  (shown in  FIG. 18B ). 
     In perspective view at top, side view (second from bottom), and top view (second from top), several external slots  316   c  are formed forwardly to ribs  316   a.    
     As best seen in cross-section views C-C and D-D, stopping ribs  315   r  will interact with the syringe-support  360  and ends its distal movement thus stopping needle penetration. 
       FIG. 18B  illustrates needle shield  320  having arms  327  terminating in fingers  321  and its protrusions  321   d.    
     Ring  326  is the terminal distal end of the device after removal of the NS remover, and will contact the injection site. 
     Activation slopes  323  will interact with counterpart activation slopes  361  of the syringe-support  360 , to release and allow movement of syringe-support  360 . 
     A pair of external longitudinal ribs  324  are formed on the needle shield  320 , interacting with slots  316   b  of the main housing  310  to guide the needle shield  320  axial movement. 
     As best seen in cross-section views G-G and I-I, two pairs of longitudinally ribs  328   a  and  328   b  extend along the axis of the needle shield  320  guide and maintain the barrel  140  of the prefilled syringe  100  centered within the lumen of the device  30 . 
       FIG. 18C  illustrates external part  340  of the NS remover, and internal part  343  of the NS remover. Snap teeth  341  are shown, which grips the NS to allow removal of the NS along with NS remover parts  340 ,  343 . 
     Longitudinal guiding ribs  347  of the internal part  343  of the NS remover are received by slots  329  of the needle shield  320 . 
     As can be seen in section View M-M damping and secure clamping of external and internal NS remover parts  340  and  343  respectively, to one another, is ensured by the presence of flexible teeth  348   e  on external part  340  and ratchet teeth  348   i  on internal part  343 . Ratchet teeth  348   i  are best shown in view N-N. Flexible teeth  348   e  engaging with ratchet teeth  348   i  may be seen on section-view  18   c.   2  and section-view N-N on the middle bottom. 
     Variations may occur during assembly of the prefilled syringe  100  components. This may result in large axial tolerance in the axial position of the NS  110 , relative to the prefilled syringe barrel  140  and flange  120 . In addition, various tolerances occur in the SAN-P  30  parts and during assembly of the SAN-P. Therefore, the NS distal rigid rim  112  may be located at various distances relative to the NS remover stopper  316   a  of the main housing  310 . 
     This is overcome in the 3rd and the 4th embodiments described herein (in  FIGS. 17-32 ) by using a two-part NS remover, having an internal part  343  and an external part  340  which are engaged through ratchet teeth  348   i  of the NS remover internal part  343  and flexible teeth  348   e  of the NS remover external part  340 . The ratchet mechanism enables engagement of the two parts during assembly at the required axial position, while having them lock for removal of the 
     NS  110 . The ratchet mechanism can be alternatively produced with the ratchet teeth on the external part  340  and flexible teeth on the internal part  343 . Alternatively, the ratchet mechanism may be replaced by any other type of connection, e.g., by heat welding, gluing, and other types of connections preferably done after assembly. 
       FIG. 18D  illustrates the syringe-support  360 . In this embodiment, syringe-support  360  includes a syringe flange seat  368  slot and syringe supporting rim  367 , which are open at one side to accept an inserted prefilled syringe  100  and its flange  120 . 
     In isometric view at left, syringe spring forward seat  369  is apparent, which holds syringe spring  370 . Compressed syringe spring  370  urges the syringe-support  360  distally. 
     Syringe-support  360  includes locking arms  365 . During storage, locking arms  365  enter and engage stop window  315   p  of the main housing  310  to prevent movement of the syringe-support  360 . 
     Activation slopes  361  are formed at the terminal end of locking arms  365 . When an injection is initiated by a user, activation slopes  361  slide against activation slopes  323  of the needle shield  320 , to bend locking arms  365  inward, and release them from their locking position by removing the locking arms from stop window  315   p  of main housing  310 . 
     Shoulders  364  engage with fingers  321  of the needle shield  320  during storage, to prevent distal movement of needle shield  320 . 
     In  FIG. 18E , rear cap  380  is shown, having inner guiding sleeve  385  which supports plunger rod  390  and guides plunger rod  390  axially when plunger rod is pressed by a user. 
     Syringe spring seat  382  support the proximal end of the syringe spring  370 . Note forward facing edge  381 , which prevents a user from pulling (hyper-extending) the plunger rod  390  instead of pressing it, by abutting against a front locking segments  391  of the plunger rod  390 . 
     Connection ring  383  engages rear cap  380  to main housing  310  via slot  318  (shown in  FIG. 18A , and Detail A of  FIG. 19A ). 
     In  FIG. 18F , plunger rod  390  is illustrated with flexible front locking segments  391 , and forward facing tip  392  that engages the piston  120  (not shown). 
     Referring to  FIGS. 19A and 19B , the device  30  is shown in its storage stage. To allow viewing of internal elements, the following components have been removed from the top view of  FIG. 19A : rear cap  380 , sticker  330 , and main housing  310 . For simplicity and clarification, the sticker  330  has been removed from all other views, cross-sections and enlargements of  FIGS. 19A and 19B . 
     The prefilled syringe  100  is assembled into the syringe-support  360  and is held axially in both distal and proximal directions by engagement of the syringe flange  120  within the syringe flange seat  368  slot of the syringe-support  360  as best seen in sectional view F-F. 
     Referring to Sectional View C-C, the syringe spring  370  is supported proximally on the rearward syringe spring seat  382  of rear cap  380 . The compressed syringe spring  370  urges the syringe-support  360  distally by pushing on the syringe spring forward seat  369  of the syringe-support  360 . 
     Referring to Enlargement A 19 -A 19  (left), the forward stop face  362  of the syringe-support  360  engages the stop window  315   p  of main housing  310  preventing syringe-support  360  from moving distally. 
     Referring still to Sectional View C-C, when the device is accidentally dropped, and an impact force is applied to the distal end of the device, namely to NS remover external part  340 , the rearward facing edge  342  of external part  340  will contact and transfer the impact force to the stopper  316   a  of the main housing  310  thus limiting the force transmitted to the prefilled syringe  100 . This feature reduces the chance of breakage of the syringe barrel  140  and/or it&#39;s flange  120 , which are often produced from glass. 
     Referring to the left-most view, the fingers  321  of needle shield arm  327  hold the needle shield  320  on the shoulders  364  of the syringe-support  360 , thus preventing the needle shield  320  from moving distally. 
     Referring to Enlargement “Detail A”, the rear cap  380  is engaged to the main housing  310  via connection ring  383  of the rear cap  380  which has entered slot  318  of the main housing  310 . This engagement can be of any form, such as a screw, a snap-fit, gluing, welding or any other suitable form. Alternatively, the main housing  310  and rear cap  380  can be a single unitary part or can be separated into two or more parts in other locations. 
     Referring to Sectional Enlargement D-D (lower left), the external part  340  of the NS remover snaps onto the main housing  310 , as follows: NS remover external part  340  has four internal protrusions  347  which engage into four circumferentially located slots  316   c,  which are formed adjacent to and distally of the stopper  316   a  of the main housing  310 . Protrusions  347  retain NS remover external part  340  and prevent its movement distally during storage. Such 
     Protrusions  347  and slots  316   c  can be of any number, formed as flexible snap-fits, etc. Additionally, they can be formed such that the protrusions are formed in the main housing  310  and the slots are formed in the NS remover external part  340 . 
     Alternatively, the NS remover external part  340  may be retained to the main housing  310  using a sticker that has to be removed or torn before removing the NS. The sticker can be evidence that the syringe has not been tampered with. Furthermore, the NS remover external part  340  can be welded/glued to the main housing  310  in a relatively weak welding, breakable by the user. 
     Referring to Cross-Section View F-F and “Detail B” at bottom, activation slope  361  is apparent upon the terminal end of locking arms  365  of the syringe-support  360 . This slope  361  lies opposite counterpart and proximally to activation slope  323  of the needle shield  320 . 
     Referring to  FIG. 19B . To allow viewing of internal elements, the sticker  330  has been removed from  FIG. 19B  at the top. Referring to cross-section Z-Z, the plunger rod  390  is engaged with the piston  130  at its forward facing tip  392 . This engagement can be of any form, such as a screw as shown, as a snap-fit, or any other suitable form. 
     Plunger rod locking segments  391  prevent the piston  130  from being pulled out from the prefilled syringe  100 , as such action will thrust the front locking segment tab  391  toward forward facing edge  381  of rear cap  380 , stopping pulling (hyper-extension) of the plunger rod  390 . Plunger rod  390  is guided axially in inner guiding sleeve  385  of rear cap  380 . 
     Needle shield spring  350  is supported proximally on the shield spring rearward seat  314  of main housing  310 . The needle shield spring  350  urges the needle shield  320  distally by pushing on the shield spring forward seat  322  of the needle shield  320 . 
     The NS remover internal part  343  is engaged to and grips the NS  110  which conceals the needle  106  and the needle tip  105  of the prefilled syringe  100 . 
     Referring to  FIG. 20 , the two-part NS remover ( 340 ,  343 ) has been removed by the user, along with the NS  110 . No changes have occurred in the position of any other part the SAN-P device  30 . For simplicity and clarification, the sticker  330  has been removed from all views, cross-sections and enlargements of  FIG. 20 . 
     The NS  110  has been removed by pulling the NS remover external part  340  distally in direction  1000 . NS remover internal part  343  is pulled away together with NS remover external part  340  by engagement of flexible teeth  348   e  of the NS remover external part  340  with ratchet teeth  348   i  of the NS remover internal part  343 . NS remover snap teeth  341  of NS remover internal part  343  grab the NS distal rigid rim  112  of NS  110 . 
     In order to protect the needle  106  from damage, during removing the NS remover assembly  340  and the NS  110 , the NS remover internal part  343  is guided axially on the needle shield  320  thus preventing any bending load on the needle  106 . The needle  106  remains hidden throughout this stage. It can be understood that there can be one or more NS remover snap teeth  341 . NS remover snap teeth  341  of NS remover internal part  343  keep the NS  110  within the NS remover assembly, thus preventing a potential choking hazard. 
     Referring to  FIG. 21 , (third view from top), a user initiates the injection process by pressing the SAN-P device  30  against an injection site  5000  in the distal direction  1050 . The terminal ring  326  of the needle shield  320  presses against the injection site, and is forced to move proximally in direction  1100 . To allow viewing of internal elements, the following components have been removed from the top view of  FIG. 21 : rear cap  380 , sticker  330 , and main housing  310 . For simplicity and clarification, the sticker  330  has been removed from all other views, cross-sections and enlargements of  FIG. 21 . 
     In  FIG. 21  Section J-J (second view from top), ring  326  of the needle shield  320  stops on the distal edge  310   d  of the main housing  310 . 
     In sectional view L-L and “Detail C” (bottom), and in enlarged section AB-AB on the left, during proximal movement of needle shield  320 , activation slope  323  of needle shield  320  slides against activation slope  361  of the syringe-support  360  and bends locking arms  365  inwardly. 
     Note position of slope  361  relative to slope  323 , as compared to their previous relative positions in  FIG. 19A  (bottom image and “Detail B”). 
     As shown in Enlargement AB-AB (left), this inward bending of locking arms  365  of the syringe-support  360  disengages the forward stop face  362  from within the stop window  315   p  of the main housing  310  and allows the syringe-support  360  to move distally with the prefilled syringe  100 , urged by syringe spring  370  as shown in  FIG. 22  ( FIG. 21  shows the syringe-support  360  immediately prior to distal movement). 
     Referring to  FIG. 22 , complete needle penetration has occurred. For simplicity and clarification, the sticker  330  has been removed from all other views, cross-sections and enlargements of  FIG. 22 . In bottom view and Enlargement “Detail AC”, urged by extension of the compressed syringe spring  370 , the syringe-support  360  has moved distally until the forward stop face  362  of the syringe-support  360  stops on the stopping ribs  315   r  of the main housing  310 . 
     In this position, the needle tip  105  of the prefilled syringe  100  has penetrated to the appropriate depth into the injection site  5000 , as shown in bottom view and the plunger rod  390  has moved distally together with the piston  130  of the prefilled syringe  100 . 
     Referring to  FIG. 23 , a user may now press the plunger rod  390  in direction  1300 , thereby advancing piston  130  to inject the fluid via the needle tip  105 . For simplicity and clarification, the sticker  330  has been removed from all other views, cross-sections and enlargements of  FIG. 23 . 
     The front locking segment  391  of the plunger rod  390  flexibly bends inwardly while entering into the syringe barrel  140 . 
     At the end of injection, the piston  130  reaches the front end of the syringe barrel  140  and stops, indicating to the user that the injection is complete. 
     Referring to  FIG. 24 , the device is shown in the “discard” stage, namely automatic needle shielding occurs after a user removes the SAN-P device  30  from the injection site  5000 . In the top view, rear cap  380 , main housing  310  and sticker  330  have been removed to view internal components. For simplicity and clarification, the sticker  330  has been removed from all other views, cross-sections and enlargements of  FIG. 24 . 
     When the user removes the SAN-P assembly  30  proximally away from the injection site  5000 , the needle shield  320  is urged by the needle shield spring  350 , to move distally relative to the main housing  310 . 
     As shown in upper-most illustration, distal movement of the needle shield  320  is stopped when the fingers  321  of the needle shield  320  stop upon shoulders  364  of the syringe-support  360 . 
     As shown in lowest illustration and “Detail D”, the needle shield  320  is in its most distal position, hiding the needle tip  105 . 
     The needle shield  320  is locked in this position towards proximal movement by the following mechanism: the proximal face of outward- and rearward-facing protrusions  321   d  (shown in  FIG. 18B ) of the needle shield  320  engage with cutout  312  of the main housing  310  (shown in second view from top), thus preventing the needle shield  320  from moving proximally, protecting the needle from being exposed. 
     In this state, reuse and inadvertent needle-sticks cannot occur from a used needle. 
       FIG. 25-32  illustrate a fourth Embodiment of the device, comprising an alternative interlock design, which prevents a user from pressing the plunger before complete needle penetration has occurred. This prevents premature discharge of the contents. Further, in this embodiment, an additional safety measure is included, so that once the device is removed from the injection site, a plunger one-way ratchet system prevents additional movement of the plunger. This eliminates discharge of leftover medication droplets which could contaminate the environment with hazardous medication. 
     Referring now to  FIG. 25 , an exploded view of the central components of Embodiment 4 are shown, including (left to right): NS Remover External Part  340 , NS Remover Internal Part  343 , Needle Shield  320 , Needle Shield Spring  350 , Prefilled Syringe  100 , Sticker  330 , Main 
     Housing  310 , Syringe-support  860 , Syringe Spring  370 , Interlock  550 , Rear Cap  880 , and two-component plunger comprising distal plunger  730 , and proximal plunger  720  having plunger flange for pressing the plunger. 
     Referring to  FIGS. 26A-26D , enlargements of the central components of the invention are presented, as follows: 
     Referring to  FIG. 26A , syringe-support  860  is shown. As shown in isometric views at far right, syringe-support is generally similar to that of Embodiment 3, described in relation to  FIG. 18D , including syringe flange seat  868  slot and syringe supporting rim, which are open at one side to accept an inserted syringe  100  and its flange  120 . Also included are locking arms  865  with activation slope  861 , which release the syringe-support from their locking position in the stop window  315   p  of the main housing  310 , when an injection is triggered by a user. 
     However, syringe-support  860  has novel lengthened release fingers  863  are shown in  FIG. 26A  (isometric view far right), which interact with an alternatively designed interlock  550 . 
     Referring to  FIG. 26B , rear cap  380  is shown enlarged. Rear cap  380  is interchangeably denoted by either one of reference numerals  380  and  880 . 
     Rear cap  880  includes through-holes  887   a  and parallel through-hole  887   b  which accept and support pivot hinge  559  of interlock  550  (pivot shown in  FIG. 26D ). Through-holes  887   a  and  887   b  support interlock  550  to allow pivoting motion of interlock  550  upon the interlock pivot axis formed by pivot hinge  559 . The pivoting motion either locks or releases the interlock from its hold on the proximal plunger  720 . 
     Syringe spring rearward seat  882  is shown in section S-S (middle view). 
     Plunger Engagement Fingers  884  of the Rear Cap  880  are shown in Section AF-AF. The engagement fingers  884  prevent proximal movement of the Proximal Plunger  720  (extension of plunger instead of pressing of the plunger). The engagement fingers  884  lean distally against the Locking Faces  726  of Proximal Plunger  720 , as shown in  FIG. 27B , central illustration (Section B 27 . 1 -B 27 . 1 ). 
     Ribs  888  of Rear Cap  880  oppose the flexible Load Beam  558  of the Interlock  550 , and during release of the interlock  550  (described in relation to  FIG. 30 ), load beam  558  of the interlock  550  is brought into pressure against ribs  888 , generating tension or preload to re-lock the proximal plunger  720  by the interlock  550  when the needle shield  320  has moved distally to discard position. 
     Referring now to  FIG. 26C , dual component plunger is shown, including the Proximal Plunger  720  and the Distal Plunger  730 . 
     A certain amount of movement of the plunger components  720  and  730  with respect to one another, is allowed during storage, to allow for tolerances in positioning during the filling process of the Prefilled Syringe  100  and changes in air pressure (as described hereinabove in relation to  FIG. 11B ). Movement may occur between Minimal Air Point  723  up to the Maximal Air Point  724  of the Proximal Plunger  720  (best shown in cross-section Y-Y). 
     Novel locking teeth  725  are included on the proximal plunger  720 , into which an Interlock locking Tooth  557  enters to lock the proximal plunger  720  from being prematurely pressed by a user. 
     Referring to lower-most sectional view Y-Y, to allow a user to timely press the plunger, proximal plunger  720  interacts with and moves distal plunger  730 , via internal Ratchet Teeth  721  of Proximal Plunger  720 , which engage with paired terminal Ratchet Teeth  732  of the distal plunger  730 . This engagement is achieved by deflecting inwardly the Flexible Fingers  735  of the distal Plunger  730  on which the paired Ratchet Teeth  732  are formed. 
     In Section AG-AG (third from bottom), Locking Faces  726  of the Proximal Plunger  720  are shown, that engage the Plunger Engagement Fingers  884  of the Rear Cap  880  to prevent proximal movement of the Proximal Plunger  720  (extension of the lounger instead of pressing of the plunger). 
     Referring to  FIG. 26D , lower isometric views, Interlock  550  of an alternative design is shown having a solitary terminal locking tooth  557  which enters locking teeth  725  of the proximal plunger  720  to prevent pressing of the plunger  720  by a user, prior to needle penetration, and during discard. 
     Interlock  550  includes a pair of Pivot Hinges  559  extending outwardly there-from. Pivot Hinges  559  enter and are supported by through-holes  887   a  and  887   b  of the rear cap  880 . The Interlock  550  is urged by movement of the paired bracing legs  556 , and by tension applied to Flexible Loading Beam  558 , to pivot upon the axis provided by pivot hinges  559 . This either releases or locks the proximal plunger  720  by interlock  550 , by inserting or removing the solitary terminal locking tooth  557  from within the proximal plunger  720  locking teeth  725 . 
     Referring to isometric view at top right, a cross-shaped Guiding Hole  555 , is designed to mate with lengthened release fingers  863  of the Syringe-support  860 . Thus, via this interaction, the syringe-support  860  prevents solitary terminal locking tooth  557  from exiting the proximal plunger  720  locking teeth  725 , until the syringe-support  860  has advanced towards the injection site and removed lengthened release fingers  863  from guiding hole  555  of the interlock  550 . The user will not succeed in pressing the proximal plunger  720  until the syringe-support  860  has advanced the needle to a complete penetrating position. 
     Referring now to  FIG. 27A , central components are shown of the fourth embodiment of the device, after assembly and in the storage position. The following components have been removed, for viewing of internal components: the rear cap  880 , the viewing window sticker  330  and the main housing  310 . For simplicity and clarification, the sticker  330  has been removed from all other views, cross-sections and enlargements of  FIG. 27A . Additionally, views and cross-sections were enlarged in different scales for increased clarification. 
     The Prefilled Syringe  100  is assembled into the Syringe-support  860  and is held axially in both distal and proximal directions by the Syringe Flange  120  engaging within the Groove  868  of the Syringe-support  860 . 
     The Prefilled Syringe  100  is axially supported by and is allowed to slide upon two pairs of longitudinally Ribs  328   a  and  328   b  which are formed internally within the Needle Shield  320 . 
     The Syringe Spring  370  is supported proximally on the Syringe Spring Backward Seat  882  of the Rear Cap  880 . The Syringe Spring  370  urges the Syringe-support  860  distally by pushing on the Syringe Spring Forward Seat  869  of the Syringe-support  860 . 
     The Forward Stop Face  862  of Syringe-support  860  engages in the Stop Window  315   p  of the Main Housing  310 , thus preventing the Syringe-support  860  from moving distally. 
     Snap Fingers  321  of the Needle Shield Arms  327  of the Needle Shield  320  hold the Needle Shield  320  on the Shoulder  864  of the Syringe-support  860 , thus preventing the Needle Shield  320  from moving distally. 
     The Rear Cap  880  is engaged to the Main Housing  310  by Connection Ring  883  of the 
     Rear Cap  880  on Slot  318  of the Main Housing  310 . This engagement can be of any form, such as a screw, a snap-fit, gluing, welding or any other suitable form. Alternatively, the Main Housing  310  and Rear Cap  880  can be a unitary part or separated into two or more parts in other locations. 
     Referring to  FIG. 27B , for simplicity and clarification, the sticker  330  has been removed from all views, cross-sections and enlargements. Additionally, views and cross-sections were enlarged in different scales for increased clarification. 
     As shown in section B 27 -B 27 , during storage, the distal plunger  730  has not yet engaged the proximal plunger  720 , and these components are allowed to move somewhat relative to one another, to allow for the tolerances or change in axial position of the Syringe 
     Piston  130  at this stage. The paired terminal Ratchet Teeth  732  of the Distal Plunger  730 , are not engaged in the counter-part internal Ratchet Teeth  721  of the Proximal Plunger  720 . A storage positioning range of the Distal Plunger  730  is defined by points Min Air  723  up to the Max Air  724  of the Proximal Plunger  720 , allowing for the positioning tolerances as explained hereinabove. 
     Plunger Engagement Fingers  884  of Rear Cap  880  lean distally against Locking Faces  726  of Proximal Plunger  720  thus preventing the proximal movement of the Proximal Plunger  720 . 
     The Distal Tip  733  of the Distal Plunger  730  is connected by any method of bonding, welding, threading, one or more snaps, etc. to the Syringe Piston  130 . 
     The Needle Shield Spring  350  is supported proximally on the Shield Spring Backward Seat  314  of the Main Housing  310 . The Needle Shield Spring  350  urges the Needle Shield  320  distally by pushing on the Shield Spring Forward Seat  322  of the Needle Shield  320 . 
     NS Remover Internal Part  343  is engaged to the NS  110  which conceals the Needle  106  and the Needle Tip  105  of the Prefilled Syringe  100 . 
     Because the NS  110  axial position results in large axial tolerance, the NS Distal Rigid Rim  112  position may vary relative to the NS Remover stopper  316   a  of the Main Housing  310 . Therefore a two-part NS remover is described, having an Internal Part  343  and an External Part  340  which are engaged through Ratchet Teeth  348   i  of the NS Remover Internal Part  343  and Flexible Teeth  348   e  of the NS Remover External Part  340 . The ratchet mechanism enables engagement of the two parts during assembly at the required axial position, while having them lock for removal of the NS  110 . 
     In case of shock applied through accidental drop on the distal end of the NS Remover  340 , the NS Remover External Part  340  of the NS remover assembly  340  will come in contact with the NS remover stopper  316   a  of the main housing  310  thus limiting the force transmitted via NS Remover  340  to the prefilled syringe  100 .This feature reduces chances for breakage of the Syringe Barrel  140  and/or it&#39;s Flange  120 , which may be produced from glass. 
     Referring back to  FIG. 27A , enlarged section D-D at bottom left, NS Remover External Part  340  has four internal Protrusions  347  which engage into four circumferentially located Slots  316   c,  which are formed adjacent to and distally of the Stopper  316   a  of the Main Housing  310 . 
     Protrusions  347  retain NS Remover External Part  340  and prevent its movement distally during storage. Such Protrusions  347  and Slots  316   c  can be of any number, formed as flexible snap-fits, etc. Additionally, they can be formed such that the protrusions are formed in the Main Housing  310  and the slots are formed in the NS Remover External Part. 
     Alternatively, the NS Remover External Part  340  may be fit to the Main Housing  310  using a sticker that has to be removed or torn before removing the NS. The sticker can be evidence that the syringe has not been tampered with. Furthermore, the NS Remover External Part  340  can be welded/glued to the Main Housing  310  in a relatively weak welding, breakable by the user. 
     Sticker  330  is attached on the Main Housing  310 . The Sticker  330  can be made of transparent material, opaque, or partially opaque. The SAN-P device  40  can be also produced without a Sticker  330 , or with another external component preferably made of plastic, alternatively to sticker  330 . 
     Referring to  FIG. 27B , Detailed Enlargement cut-away “Detail  27   c ”, the Interlock  550  is engaged inside the Rear Cap  880  by engagement of Pivot Hinges  559  in Holes  887   a  and  887   b  of Rear Cap  880  such that Locking Tooth  557  of Interlock  550  is facing inwardly and proximally. 
     Referring to  FIG. 27C , for simplicity and viewing of internal components isometric side-view is shown without the following components: the two-part NS Remover ( 340 ,  343 ), the rear cap  880 , the viewing window sticker  330  and the main housing  310 . For simplicity and clarification the sticker  330  has been removed from the bottom view, and cross-sections A 1 -A 1  and A 2 -A 2  are shown enlarged. 
     As seen in “Detail  27   c   1 ”, the Flexible Beam  558  of the Interlock  550  is positioned such that it is unloaded, lying in its natural position facing outwardly towards internally facing Ribs  888  of Rear Cap  880 . 
     One of lengthened release fingers  863  of the Syringe-support  860  is located within guiding hole  555  of the interlock  550 . The other finger  863  is not functional and is only shown for simplifying the production process by allowing assembly of the syringe-support  860  in two orientations. 
     Paired bracing legs  556  of the Interlock  550  (which are outwardly and inwardly facing), are positioned such that they are unloaded, lying in their natural position. 
     Referring to  27 C, Section A 2 -A 2 , the Proximal Plunger  720  is blocked from moving distally by engagement of the Interlock&#39;s Locking Tooth  557 , within the Forward Facing Edge  727  (indicated in  FIG. 29B  Section B 2 -B 2 ) of the proximal plunger locking teeth  725 . This feature reduces the risk of user error (premature plunger press and premature discharge of fluid) as this prevents unintended spill-out of medication through the needle before the needle has penetrated the injection site. Such premature fluid or medication spill-out may cause an under-dose of medication, or skin irritation. 
     Referring to  FIG. 27C , isometric side-view “Detail  27   c   1 ”, the lengthened release finger  863  of the Syringe-support  860 , ensures the Locking Tooth  557  of the Interlock  550  won&#39;t move outwardly away from the Proximal Plunger  720  as long as the lengthened release finger  863  is positioned within the Guiding Hole  555  of the interlock  550 . 
     Referring now to  FIG. 28 , for simplicity and clarification the sticker  330  has been removed from the side view (shown in the middle), and the cross-sections G-G and I-I. In  FIG. 28  the two-part NS Remover ( 340 ,  343 ) has been removed by the user, along with the NS  110 . No changes have occurred in the position of any other part the SAN-P device  30 . 
     The NS  110  has been removed by pulling the NS Remover External Part  340  distally in direction  1000 . NS Remover Internal Part  343  is pulled away together with NS Remover External Part  340  by engagement of Flexible Teeth  348   e  of the NS Remover External Part  340  with Ratchet Teeth  348   i  of the NS Remover Internal Part  343 . NS Remover Snap Teeth  341  of NS Remover Internal Part  343  grab the NS Distal Rigid Rim  112  of NS  110 . 
     In order to protect the Needle  106  from damage, during removing the NS Remover assembly  340  and the NS  110 , the NS Remover assembly  340  is guided axially on the Needle Shield  320  thus preventing any bending load on the Needle  106 . The Needle  106  remains hidden throughout this stage. It can be understood that there can be one or more NS Remover Snap Teeth  341 . NS Remover Snap Teeth  341  of NS Remover Internal Part  343  keep the NS  110  within the NS Remover assembly, thus preventing a potential choking hazard. It can be understood that there can be one or more NS Remover Snap Teeth  341 . 
     Referring to  FIG. 29A , for simplicity and clarification the sticker  330  has been removed from the side view (shown in the middle), and all the cross-sections. In  FIG. 29A  a user initiates the injection process by pressing the SAN-P device  40  against an Injection Site  5000  in the distal direction  1050 . The terminal Ring  326  of the Needle Shield  320  is forced to move proximally in direction  1100 . 
     In top-most view, the Ring  326  of the Needle Shield  320  stops on the Distal Edge  310   d  of the Main Housing  310 . 
     In sectional view L-L, similarly to Embodiment 3, during proximal movement of Needle 
     Shield  320 , Activation Slope  323  of Needle Shield  320  slides against Activation Slope  861  of the Syringe-support  860  and bends the Locking Arm  865  inwardly. Note position of slope  861  relative to slope  323 , as compared to their previous relative positions in  FIG. 28  (right most image). 
     In Enlargement AB-AB, this inward bending of Locking Arm  865  of the Syringe-support  360  disengages the Forward Stop Face  862  from within the Stop Window  315   p  of the Main Housing  310  and allows the Syringe-support  860  to move distally with the Prefilled Syringe  100 , urged by syringe spring  370 . 
     Referring to  FIG. 29B , for viewing of internal components isometric side-view is shown without the following components: the rear cap  880 , the viewing window sticker  330  and the main housing  310 . For simplicity and clarification the sticker  330  has been removed from the bottom view, and cross-sections B 1 -B 1  and B 2 -B 2  are shown enlarged. In sectional view B 1 -B 1 , during proximal movement of Needle Shield  320 , the Needle Shield Arms  327  of the Needle Shield  320  move proximally and engage the Legs  556  of the Interlock  550  and force them to bend outwardly. 
     In  29 B, Section B 2 -B 2 , bending the Legs  556  of Interlock  550  creates a load or torque relative to the Pivot Hinges  559  of Interlock  550  urging the Locking Tooth  557  of Interlock  550  to move radially outwardly. However, radial movement of the Locking Tooth  557  of Interlock  550  is blocked by the lengthened release finger  863  of the Syringe-support  860 ; thus locking tooth  557  is still blocking the distal movement of the Proximal Plunger  720 . Any attempt to press the Proximal Plunger  720  distally and inject the drug, is thus prevented at this stage. 
     Referring to  FIG. 30A , for simplicity and clarification the sticker  330  has been removed from the center view, and cross-sections  30 A- 30 A is shown enlarged. In  FIG. 30A  complete needle penetration has occurred. In view  30 A- 30 A, urged by extension of the compressed Syringe Spring  370 , the Syringe-support  860  was urged together with Prefilled Syringe  100  by the Syringe Spring  370  and moved distally until Forward Stop Face  862  of Syringe-support  860  stops on Stopping Ribs  315   r  of Main Housing  310  (also shown in center illustration and similarly in Embodiment 3). 
     The Needle Tip  105  of the Prefilled Syringe  100  has penetrated to the appropriate depth into the injection site  5000 . 
     In  FIG. 30A , cross-section A-A, the Distal Plunger  730  which is connected to the Syringe Piston  130 , has moved, along with the Prefilled Syringe  100 . The Distal plunger  730  has engaged with the proximal plunger  720 , as follows: The paired terminal Ratchet Teeth  732  of the distal plunger  730  have moved distally and engaged with the internal Ratchet Teeth  721  of the Proximal Plunger  720 . This engagement is achieved by deflecting inwardly the Flexible Fingers  735  of the distal Plunger  730  on which the paired Ratchet Teeth  732  are formed. 
     The specific tooth engaged, from among the internal Ratchet Teeth  721  of the Proximal Plunger  720 , depends on the initial axial position of the Syringe Piston  130  and various assembly tolerances. 
     Referring to  FIG. 30B , for viewing of internal components isometric side-view is shown without the following components: the rear cap  880 , the viewing window sticker  330  and the main housing  310 . For simplicity and clarification the sticker  330  has been removed from the bottom view, and cross-sections C 1 -C 1  and C 2 -C 2  are shown enlarged. In  FIG. 30B  section C 2 -C 2 , the lengthened release finger  863  of the Syringe-support  860  has moved distally and is no longer located within the guiding hole  555  of the Interlock  550 . Therefore, the locking Tooth  557  of the Interlock  550  is allowed to move radially outwardly away from the Forward Facing Edge  727  of the Ratchet Teeth  725  of the Proximal Plunger  720 . The Proximal Plunger  720  may then move distally when pressed by a user, to perform an injection. 
     Referring to isometric view (Detail G), movement of the Tooth  557  of Interlock  550  radially outwardly, is due to the urging torque created by the bending motion of the paired bracing Legs  556  of the Interlock  550 , executed by the Needle Shield Arms  327  of the Needle Shield  320  as detailed above. 
     Due to rotation of the Interlock  550  with respect to the Pivot Hinges  559 , the paired bracing Legs  556  of Interlock  550  have become nearly unloaded, and the Load Beam  558  of the Interlock  550  is banded against the Ribs  888  of the Rear Cap  880  and become loaded urging the Locking Tooth  557  of the Interlock  550  to move back inwardly. 
     The Load Beam  558  banding force is lighter than the force required to band Legs  556 . 
     The Proximal Plunger  720  may then move distally when pressed by a user, to perform an injection as described herein-below. 
     Referring now to  FIG. 31 , for simplicity and clarification the sticker  330  has been removed from the center view, and cross-sections S-S and AS-AS. In cross-section S-S, “delivery” stage, a user may now press the Proximal Plunger  720  in the distal direction  1300 . The engagement between the internal Ratchet Tooth  721  of the Proximal Plunger  720 , with the terminal Ratchet Teeth  732  of the distal plunger  730 , forces the Distal Plunger  730  to move distally, together with the Piston  130 , therefore injecting the fluid via the Needle Tip  105 . 
     At the end of injection, the Piston  130  reaches the front end of the Syringe Barrel  140  and stops, indicating to the user that the injection is complete. 
     Referring to  FIGS. 32A and 32B , the device is shown in the “discard” stage, namely automatic needle shielding occurs after a user removes the SAN-P device  40  from the injection site  5000 . In the top view of  FIG. 32A , rear cap, main housing and sticker have been removed to view internal components. In the second view from the top, rear cap and sticker have been removed to view internal components. The sticker has been removed for simplicity in the second view from bottom and enlarged section V-V at the bottom. 
     As shown in upper-most illustration (shown enlarged), distal movement of the needle shield  320  is arrested when the Snap Fingers  321  of the Needle Shield  320  stop upon Shoulder  864  of the Syringe-support  860 . 
     At this stage, the Needle Tip  105  is safely concealed by the Needle Shield  320  and cannot be re-exposed. 
     The needle shield is locked in this position by the following mechanism: the proximal face of outward- and rearward-facing Protrusions  321   d  of the Needle Shield  320  engage with cutout  312  of the main housing  310  (shown in second view from top). In this state, reuse and inadvertent needle-sticks cannot occur from a used needle. 
     Referring to  FIG. 32B , for viewing of internal components isometric side-view is shown without the following components: the rear cap  880 , the viewing window sticker  330  and the main housing  310 . For simplicity and clarification the sticker  330  has been removed from the bottom view. In  FIG. 32B  section E 1 -E 1  the interlock position is shown in the “discard” stage. The needle Shield Arms  327  of the Needle Shield  320 , have moved distally to the “discard position”, the paired bracing Legs  556  of the Interlock  550  are no longer urged by the Needle Shield Arms  327  outwardly. The bracing legs  556  return inwardly, with Locking Tooth  557  of the Interlock  550  by the force applied by the load of Beam  558  of the Interlock  550 . 
     As shown in isometric view (Detail H), the Locking Tooth  557  engages with one of the Proximal Plunger  720  Locking Teeth  725 ; this locks the Proximal Plunger  720  from further movement distally. The plunger can no longer be pressed by a user, thus discharge of any remaining medication is prevented, to avoid biohazardous spills. 
     It can be understood, that while here the locking movement was shown in the distal direction, the locking can be similarly designed to lock towards movement in the opposite direction, i.e., the proximal direction by designing the Locking Tooth  557  and Locking Teeth  725  of the Proximal Plunger  720  in the opposite direction. 
     Referring now to  FIG. 33A-33C , another embodiment of the invention is described, in which the proximal plunger is locked in both axial directions, prior to needle penetration, and in the “discard” state. In  FIG. 33A , for viewing of internal components top view is shown without the following components: the rear cap  880 , the viewing window sticker  330  and the main housing  310 . For simplicity and clarification the sticker  330  has been removed from the both views in the center, and enlarged cross-section W-W. 
     Referring to  FIG. 33B , for viewing of internal components isometric view in the center is shown without the following components: the rear cap  880 , the viewing window sticker  330  and the main housing  310 . In the upper isometric enlargement, the interlock&#39;s terminal locking tooth is split into two terminal locking teeth  587  and  587   c,  with each tooth angled in a different direction. See enlargement of interlock at top right, where angles of teeth  587  and  587   c  are shown. 
     These two interlock teeth  587  and  587   c,  enter and engage appropriate proximal plunger external locking teeth  715  and  715   c,  which are also angled in opposite directions relative to one another. 
     This engagement locks and prevents movement of the Proximal Plunger  710  in both axial directions, so that the plunger cannot be pressed (prior to advancement of the syringe-support to a needle penetration position) and the plunger also cannot be extended. 
     In addition, as seen in  FIG. 33C  (for simplicity and clarification the sticker  330  has been removed from the view in the center, and both enlarged cross-sections AZ-AZ and AU-AU), the SAN-P device  40  is shown after its removal from the injection site  5000  before the injection was complete, either accidentally, or, for instance, when the user is required to inject a dose which is smaller than the amount prefilled in the Prefilled Syringe  100 . Thus, residual fluid  117  remains in the Prefilled Syringe  100 . 
     In this situation, as in the case where the full dose was injected (shown in previous figures), the Needle Shield  320  moves distally relative to the Main Housing  310  urged by the Needle Shield Spring  350 . The Needle Tip  105  of the Prefilled Syringe  100  is safely concealed by the Needle Shield  320 . The Needle Shield  320  is locked from axial movement in both directions, as described in relation to  FIGS. 32A and 32B  above. 
     As Needle Shield Arms  327  of the Needle Shield  320  move distally to the “discard position”, the bracing Legs  586  of the Interlock  580  are no longer urged by the Needle Shield Arms  327  outwardly and return inwardly with Locking Teeth  587  and  587   c  of the Interlock  580  by the load of Beam  588  of the Interlock  580 . The Locking Teeth  587  and  587   c  engage the Locking Teeth  715  of the Proximal Plunger  710  and lock the Proximal Plunger  710  from further movement both distally and proximally. 
     Locking the Proximal Plunger  710  in both directions may be important as some types of drugs are toxic and may cause skin irritation or local reactions if accidentally expelled onto the skin. 
     In summary, the safe auto-needle device (SAN-P) of the invention, provides a user with an inexpensive injection device, which allows a user to control the rate of injection to alleviate pain, and has various safety features: premature discharge of the medication, and discharge of remaining medicinal drops are prevented by the presence of an interlock, extension of the plunger instead of pressing it is prevented by inclusion of locking segments upon the plunger, breaking and bending of the needle is prevented by inclusion of an NS remover providing damping, automatic needle shielding is provided by the needle sheath which is locked for discard. 
     Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. 
     All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.