Abstract:
A first embodiment of an automatic injector employs less material and fewer parts by eliminating an outer housing required in earlier automatic injectors. In a second embodiment, a manually operated sharps protector is provided. In a third embodiment, the sharps protector is deployed by a spring positioned internally of the sharps protector. In a fourth embodiment, the sharps protector is deployed by a spring positioned externally of the sharps protector. In all embodiments, removal of a safety cap enables a user to press on an outer gun sleeve that displaces in an axial direction and releases the trailing end of a spring holder so that a compressed spring that bears against the spring holder unloads and drives a piston that displaces a cannula into the tissue of a user, followed by a liquid medicament injection through the cannula.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to improvements in automatic injectors. Additional embodiments include a sharps protector that is manually or automatically operable. 
     2. Description of the Prior Art 
     Military personnel under chemical attack are trained to use automatic injectors when an injection is needed on an emergency basis in the field where medical personnel are not available to perform the injection. Civilians or military personnel who are allergic to bee or wasp stings, and the like, may use them when there is no access to emergency medical service (EMS) personnel or insufficient time to travel to a medical facility. Passenger aircraft are often equipped with automatic injectors as well for use when a passenger has a food allergy that creates a medical emergency. Most emergency medical vehicles also carry automatic injectors for the emergency treatment of allergic reactions. There are other uses for automatic injectors as well. 
     The automatic injector disclosed in expired U.S. Pat. No. 4,031,893, commercially known as the EpiPen® epinephrine auto-injector, invented primarily by the present inventor, has been in widespread use for more than twenty years. The military version thereof is known as the Pralidoxime ComboPen. The user grasps an outer cylindrical sleeve of the injector and delivers the leading end of the device to the injection site with a force sufficient to cause release of a spring-loaded needle. More specifically, when the device is ready to be used, the outer cylindrical sleeve trails an inner cylinder from which the needle or cannula extends so that when the leading end of the outer cylindrical sleeve hits the user&#39;s skin, the movement of the trailing end of the outer cylindrical sleeve releases a spring and the spring drives a piston that pushes liquid medicament out of a cartridge and Into the user&#39;s tissue through the cannula. 
     The &#39;893 device fulfilled the needs of its (pre-AIDS) time, but it includes no means for covering the sharp cannula after it has been deployed. Thus, the exposed cannula represents a hazard to those who come into contact with it after it has been withdrawn from the tissue of the user. Nor is it a simple matter to retrofit the cannula with a sharps protector because there is insufficient space within which to mount a sharps protector. 
     The &#39;893 device also uses a relatively large amount of plastic material in its construction due to the aforesaid outer cylindrical sleeve. 
     Another drawback of the &#39;893 device is that the user must aim at and hit the desired point of injection in one motion. Impact of the device against the user&#39;s body triggers extension of the cannula by causing the release of a loaded piston biasing means if the device works in accordance with its design. 
     Premature deployment is therefore a problem. For example, the cannula may deploy when the device is placed on any site with slight pressure or when brushed against a surface such as a wrinkle in a pair of trousers. Deformed or misaligned parts may cause such unwanted premature deployment. Such premature activation, caused by the inadvertent application of a slight amount of pressure, is clearly unwanted. 
     Accordingly, there is a need for an improved automatic injector having a design that reduces the chances of a premature cannula deployment. 
     There are also a number of factors that can result in a failure of the cannula to deploy properly. For example, the cannula may fail to properly deploy if the auto-injector spring is weak, if the cannula is occluded, if a glass medicament-containing ampule breaks, if the piston sticks to the interior surface of the glass walls of the cartridge holder sleeve, if the device otherwise jams due to a parts misalignment, or the like. 
     A need therefore exists for an automatic injector having a design that reduces the chances of an improper cannula deployment. 
     Astronaut suits and other special clothing items include a special (self-sealing) area of the clothing designed to accept a cannula so that an emergency injection may be performed in the absence of a need to remove the clothing. The special area is small and not easy to hit when performing an emergency injection. 
     Thus there is a need for an automatic injector that would enable the user to position the leading end of the device in juxtaposition with an intended injection site before the needle is triggered. 
     Moreover, an automatic injector having means for shielding the deployed cannula is needed. 
     A good design also minimizes the use of natural resources, especially in devices that are used only once and discarded or re-cycled. 
     A need therefore exists for an automatic injector formed of less material than the automatic injectors of the prior art. 
     The medicament in an automatic injector may become cloudy due to age or some other cause. it may even leak out of the automatic injector if the ampule that contains such medicament has been damaged. When cloudy or discolored in any way, or if not present in its full effective quantity, the efficacy of the medicament is in doubt. Accordingly, pre-injection visual inspection of the medicament is required to ascertain whether or not it is present and suitable for use. Some of the known automatic injectors such as the EpiPen® have somewhat clear, semi-transparent parts that enable visual inspection of the medicament, but there are three layers of said parts (an outer cylindrical sleeve, a cartridge holder sleeve, and the medicament-containing ampoule). The outer cylindrical sleeve and the cartridge holder sleeve are formed of natural plastic and thus are semi-transparent. The ampoule is formed of clear glass. Thus, if either of the outer two parts become cloudy or otherwise lose at least some degree of transparency, visual inspection of the medicament is hindered. 
     Thus, there is a need for an automatic injector made of fewer parts so that pre-injection visual inspection of medicament does not require looking through three layers of parts. 
     An automatic injector can also fail because the medicament contained therewithin may fail to reach the tissue of the patient in whole or in part due to various mechanical malfunctions of the device. For example, it is possible for the cannula to deploy but for none of the medicament, or just a fraction thereof, to actually flow through the cannula into the patient&#39;s tissue. 
     Accordingly, there is a need for an automatic injector made of fewer parts so that post-injection visual inspection of medicament does not require looking through three layers of parts. 
     From a mechanical standpoint, the more parts a device has, the greater are the chances for a malfunction. 
     Thus there is also a need for an automatic injector having fewer parts to increase its reliability of operation. 
     However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the identified needs could be fulfilled. 
     SUMMARY OF INVENTION 
     The long-standing but heretofore unfulfilled need for an automatic injector that is constructed of less materials, that has fewer parts, that may be positioned at a preselected location prior to release of the cannula, that provides sharps protection, and that otherwise advances the art is now met by a new, useful, and nonobvious invention. 
     A cartridge holder sleeve has a lumen that slideably receives a cartridge, a piston, a spring holder, and an inner gun sleeve. The cartridge is adapted to hold a liquid medicament. A cannula hub is mounted to a leading end of the cartridge, and a cannula is mounted to a leading end of the cannula hub. The piston is disposed in trailing relation to the cartridge and the spring holder is disposed in trailing relation to the piston. 
     A first diameter-reducing shoulder is formed in the cartridge holder sleeve near a leading end thereof. Accordingly, a reduced diameter section of said cartridge holder sleeve is formed in leading relation to said first diameter-reducing shoulder. 
     A spring-retaining shoulder is formed in the spring holder near a leading end thereof. The spring holder further includes a plurality of longitudinally extending parallel legs that extend in trailing relation to the shoulder. 
     A leading end of the inner gun sleeve is positioned within the lumen and a trailing end is positioned external to the lumen. In some embodiments, a truncate outer gun sleeve engages the trailing end of the inner gun sleeve. A safety cap is mounted to the outer gun sleeve, and said safety cap includes a safety pin that extends through a central aperture formed in the outer gun sleeve into a space surrounded by the parallel legs of the spring holder. 
     A piston biasing means under compression has a leading end disposed in abutting relation to the spring-retaining shoulder of the spring holder and a trailing end disposed in abutting relation to a trailing end of the inner gun sleeve. The trailing end of the inner gun sleeve is adapted to releasably engage the respective trailing ends of the parallel legs of the spring holder. 
     When the safety cap and hence the safety pin are removed, manual pressure applied against the outer gun sleeve in a trailing-to-leading direction effects radially inward travel of the parallel legs of the spring holder, thereby releasing the piston biasing means and driving the cannula into the tissue of the user. 
     The cannula, cartridge, piston, and spring holder are positioned within the lumen of the cartridge sleeve holder, toward the trailing end thereof in a retracted position, when the piston biasing means is under compression. Said parts slide abruptly toward the leading end of the lumen when the piston biasing means unloads. The cannula extends out of the lumen in leading relation to the leading end of the cartridge sleeve holder when the piston biasing means is in repose, i.e., not under compression. 
     In a first embodiment, a manually operated releasing means disengages the trailing end of the spring holder from the trailing end of the inner gun sleeve so that the piston biasing means unloads when the releasing means is activated. The structure of the first embodiment eliminates the outer cylindrical sleeve of the automatic injector disclosed in the above-mentioned expired patent. 
     In a second embodiment, a sharps protector is mounted to the cartridge holder sleeve on the reduced-diameter section thereof. 
     The sharps protector has a first, retracted position where a leading end of the sharps protector is substantially co-extensive with a leading end of the cannula when the cannula is in a retracted position. The sharps protector has a second, extended position where a leading end of the sharps protector is substantially co-extensive with a leading end of the cannula when the cannula is in an extended position. 
     A user of the automatic injector manually displaces the sharps protector from the first, retracted position to the second, extended position after the release means has been activated. 
     More particularly, an annular detent means is formed in a trailing end of the manually operated sharps protector. A first annular recess is formed in the reduced diameter part of the cartridge holder sleeve, and the first annular recess receives the annular detent means when the sharps protector is in its retracted configuration. A second annular recess is formed in said reduced diameter part of the cartridge holder sleeve in leading relation to the first annular recess. The second annular recess receives the annular detent means when the sharps protector is manually displaced into its extended configuration. 
     In a third embodiment, a second diameter-reducing annular shoulder is formed in the reduced diameter section of the cartridge holder sleeve in leading relation to the first diameter-reducing shoulder and a diameter-reducing taper is formed in the reduced diameter section of the cartridge holder sleeve in leading relation to the second diameter-reducing shoulder. The second diameter-reducing shoulder provides a stop means for the trailing end of an internally mounted sharps protector biasing means, which may take the form of a coil spring, for automatically deploying the sharps protector. 
     The sharps protector biasing means has a lumen that receives the downwardly-tapered leading end of the cartridge holder sleeve. The sharps protector biasing means has a trailing end that abuts the second diameter-reducing shoulder and a leading end that abuts the leading end of the sharps protector, internally thereof. 
     In the third embodiment; a first latch means, formed of a pair of diametrically opposed first latch members, is formed in a trailing end of the sharps protector and is separated from the sharps protector along a parting line at a leading end and opposite sides of each first latch member. A trailing end of each first latch member forms a living hinge with the sharps protector and the leading end of each first latch member extends into a first catch means to prevent unloading of the sharps protector biasing means. The first catch means includes a pair of diametrically opposed slots or catch members formed in the reduced diameter section of the cartridge holder sleeve. 
     Accordingly, retraction of the leading end of each first latch member from its associated first catch member enables unloading of the sharps protector biasing means and deployment of the sharps protector to its fully extended position where the deployed cannula is fully housed therewithin. 
     A pair of diametrically opposed accommodation slots is formed in the sharps protector in spaced apart, leading relation to the first catch members. A stop means includes a pair of diametrically opposed stop members. Each stop member is separated from the sharps protector along a parting line at a trailing end and opposite sides of each stop member, leaving a living hinge at the leading end of each stop member. The trailing end of each stop member extends into its associated accommodation slot when the sharps protector biasing means is under load and the sharps protector is in its retracted position. The trailing end of each stop member extends into its associated second catch member when the sharps protector biasing means is unloaded and the sharps protector is in its deployed position, thereby preventing displacement of the sharps protector in a leading-to-trailing direction. 
     A pair of diametrically opposed elongate guide slots are also formed in the reduced diameter section of the cartridge holder sleeve. A pair of diametrically opposed detent means is formed in the trailing end of the sharps protector. Each detent means slideably engages an associated guide slot. 
     In a fourth embodiment, the trailing end of an externally mounted sharps protector biasing means abuts the first diameter-reducing annular shoulder and the leading end of the externally mounted sharps protector biasing means abuts the trailing end of the sharps protector. The arrangement of latch members, catch members, stop members, and detents that control operation of the third embodiment also forms a part of the fourth embodiment. 
     An important object of this invention is to improve the design and hence lower the cost of conventional automatic injectors by substantially reducing the amount of materials used to make them. 
     Another important object of this invention is to provide an automatic injector having manually deployable means for covering a deployed cannula. 
     Still another important object is to provide an automatic injector having automatically deployable means for covering a deployed cannula. 
     Yet another object is to provide different embodiments of the automatic injector so that in a first embodiment the cannula may be placed into position with an injection site prior to activation of the cannula extending means and so that in a second embodiment the act of delivering the leading end of the auto injector to the injection site results in automatic deployment of the cannula. 
     These and other important objects, advantages, and features of the invention will become clear as this description proceeds. 
     The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts that will be exemplified in the description set forth hereinafter and the scope of the invention will be indicated in the claims. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which: 
     FIG. 1A is a longitudinal sectional view of the leading end of a prior art auto-injector when an unillustrated piston biasing means is loaded; 
     FIG. 1B is a view like that of FIG. 1A but when the unillustrated piston biasing means has been unloaded, driving the cannula into its deployed position; 
     FIG. 2 is a longitudinal sectional view of a first embodiment of the invention; 
     FIG. 3 is an exploded perspective view of some of the parts of said first embodiment; 
     FIG. 4 is a transverse sectional view taken along line  4 — 4  in FIG. 2; 
     FIG. 5 is a sectional view of the manually deployable sharps protector when in its undeployed configuration; 
     FIG. 6 is a longitudinal sectional view taken along line  6 — 6  in FIG. 5; 
     FIG. 7 is a longitudinal sectional view of the sharps protector of FIG. 5 when in its deployed configuration; 
     FIG. 8 is a longitudinal sectional view of an embodiment of the manually deployable sharps protector having an elongated inner gun sleeve when the cannula is in its undeployed configuration; 
     FIG. 9 is a longitudinal sectional view of an embodiment where the sharps protector is deployable by a sharps protector biasing means mounted within the sharps protector and where neither the cannula nor the sharps protector are deployed; 
     FIG. 10 is a transverse sectional view taken along line  10 — 10  in FIG. 9; 
     FIG. 11 is a longitudinal sectional view like that of FIG. 10 but where the cannula is deployed and the automatically deployable sharps protector remains undeployed; 
     FIG. 12 is a transverse sectional view taken along line  12 — 12  in FIG. 11; 
     FIG. 13 is a longitudinal sectional view like that of FIG. 11 but where both the cannula and the sharps protector are deployed; 
     FIG. 14 is a longitudinal sectional view of an embodiment of the novel automatic injector where a sharps protector biasing means for automatically deploying the sharps protector is mounted externally of the sharps protector; 
     FIG. 15 is a side elevational view of an alternative embodiment of the FIG. 14 embodiment, depicting an elongated inner gun sleeve in phantom lines; 
     FIG. 16 is a view like FIG. 15 depicting a shortened version of the elongated gun sleeve to enhance pre-firing visual inspection of the medicament; and 
     FIG. 17 is an exploded perspective view of the leading end of the cartridge holder sleeve and the sharps protector. 
    
    
     DETAILED DESCRIPTION 
     Referring first to prior art FIG. 1A, it will there be seen that the stroke of the outer cylindrical sleeve  8  of the EpiPen® auto-injector and its military counterpart, the Pralidoxime ComboPen, is denoted by a pair of confronting arrows labeled by the letter “S.” The in-repose position of outer cylindrical sleeve  8  is cross-hatched and the momentary forward position said sleeve  8  attains when the user activates the device is depicted in unhatched lines and is denoted  8   a.    
     When needle  22  is deployed, as depicted in FIG. 1B, outer cylindrical sleeve  8  returns to its FIG. 1A in-repose position after only momentarily attaining said  8   a  position. 
     The EpiPen® auto injector and its military counterpart both lack sharps protection as mentioned earlier. If a sharps protector were simply retrofit onto said devices, as indicated in FIG. 1A, only the distance denoted “P” would be available to accommodate said sharps protector, depicted in phantom lines and denoted  9 , and said distance would be clearly inadequate for the reasons that follow. 
     Distance “P” is measured from an unnumbered annular shoulder to the distal free end of the auto injector. Said annular shoulder is positioned about mid-way of the length of cannula  22 , radially outwardly thereof, when said cannula  22  is in its FIG. 1A retracted or undeployed position. The leading end of cartridge  14  is substantially co-extensive with said annular shoulder, radially outwardly thereof, when cannula  22  is extended or deployed as depicted in FIG.  1 B. 
     As further indicated in FIG. 1B, if hypothetical sharps protector  9  were manually deployed, only a very short length thereof, denoted “L,” would be available to engage the trailing end of said sharps protector. Sharps protector  9  would thus not be securely attached to the auto injector and could not be relied upon to perform its intended function. The length denoted “B” indicates a bevel formed in the leading end of the auto injector; said beveled area is not available as a mounting surface for sharps protector  9 . The distance denoted “R” is the amount by which cannula  22  is recessed from the distal end of sharps protector  9  when said cannula  22 , having an exposed length denoted “N,” is deployed. Recess “R” would be inadequate to protect the sharp distal end of cannula  22  in all handling situations because it is shallow. 
     If a sharps protector were simply retrofit onto the EpiPen® and its military counterpart, the approximate dimensions of the above-described distances would be as follows: Stroke distance “S” would be about 0.09 inches; Protector-accommodating distance “P” would be about 0.89 inches; Accommodating length “L” would be about 0.06 inches; Beveled distance “B” would be about 0.12 inches; Exposed needle length “N” would be about 0.65 inches; and Recess “R” length would be about 0.06 inches. Thus, it would not have been obvious to add a sharps protector to such devices because the dimensions thereof are inadequate to adequately support a sharps protector. Nor would it have been obvious to re-design such devices so that they could accommodate a sharps protector because such re-designing could not be accomplished by a mere enlarging of the dimensions of the devices. 
     Referring now to FIGS. 2-4, it will there be seen that the reference numeral  10  denotes an illustrative embodiment of the novel automatic injector. This first embodiment improves upon the devices of the prior art but does not include a sharps protector. 
     By comparing FIG. 2 with FIGS. 1A and 1B, it will be observed that outer cylindrical sleeve  8  is eliminated, thereby saving materials and eliminating the need to aim the auto injector carefully at a target injection site. It will also be observed that the unnumbered annular shoulder against which the leading end of said sleeve  8  abuts is eliminated, thereby freeing up a large extent of the auto injector for accommodating a sharps protector. 
     Automatic injector  10  includes cartridge holder sleeve  12  having lumen  13 . A reduced-diameter section  15  of cartridge holder sleeve  12  is formed by first diameter-reducing annular shoulder  17 . Annular shoulder  17  is set far back from leading end  12   a  of cartridge holder sleeve  12 . However, it should be understood from the outset that annular shoulder  17  is an optional, i.e., non-critical feature of the novel device and the benefits of the invention may be realized even if said annular shoulder is eliminated. Where shoulder  17  is obviated, a plurality of radially outwardly projecting splines, not shown, or other suitable stop means, could perform the stop function of said shoulder. 
     Lumen  13  slideably receives cartridge  14  that is filled with liquid medicament  16 . 
     When slideably-mounted piston  18  is displaced in a trailing-to-leading direction, as indicated by single-headed directional arrow  20 , liquid medicament  16  is expelled from cartridge  14  so that it flows into cannula  22 . 
     Cartridge  14  is interconnected to cannula  22  by cannula hub  24 . Flexible and resilient sheath  26  houses cannula  22 . Sheath  26  has a closed distal end  28 . 
     Spacer  30  has head  31  that snaps into and engages the open trailing end of piston  18 . Annular, radially inwardly-turned flange  36  formed in the trailing end of piston  18  extends radially inwardly into the open trailing end of piston  18  and prevents retraction of head  31  from said open trailing end. 
     Head  34  of spring holder  32  has a frusto-conical shape and is formed of a material that is harder than the material of which spacer  30  is formed so the trailing annular edge of frusto-conical head  34  digs into the cylindrical blind bore formed in the trailing end of spacer  30 , thereby securing head  34  within said cylindrical blind bore. Spring holder  32  and its head  34  are preferably of metallic construction and spacer  30  is preferably of plastic construction. 
     As best understood in connection with FIG. 3, shoulders  40  formed in spring holder  32  have leading surfaces, collectively denoted  40   a , that abut the trailing end of spacer  30  and trailing surfaces, collectively denoted  40   b , against which abuts leading end  42   a  of a piston biasing means which may take the form of coil spring  42  or an equivalent piston biasing means. 
     Inner gun sleeve  44  (FIG. 2) substantially houses piston biasing means  42 . Trailing end  42   b  of piston biasing means  42  abuts leading radially inwardly turned wall  46  of inner gun sleeve  44 . Accordingly, piston biasing means  42  is held in compressed relation between said inwardly turned wall  46  and trailing surfaces  42   b  of shoulders  40  of spring holder  32 . 
     An annular radially outwardly extending detent  45  is formed in inner gun sleeve  44  about mid-length thereof and said detent engages an unnumbered corresponding annular recess formed in an interior cylindrical wall of cartridge holder sleeve  12 . This interconnects said inner gun sleeve  44  and cartridge holder sleeve  12 . 
     In this embodiment, annular radially outwardly extending detent  47  is formed in inner gun sleeve near the trailing end thereof. 
     Metal washer  48  is part of the assembly that prevents piston biasing means  42  from unloading when automatic injector  10  is not in use. The outer periphery of washer  48  is captured by a washer-gripping member that includes leading radially inwardly turned wall  46  and trailing radially inwardly turned wall  50 . An annular washer-retaining recess is defined between said two walls. The annular recess is unnumbered to avoid cluttering the drawings. 
     Spring holder  32  includes a plurality of equidistantly and circumferentially spaced apart legs, collectively denoted  52 , that are disposed in parallel relation to one another. Each leg has a radially outwardly turned detent  54  formed near its trailing end. A recess  55  is formed in each leg  52  on the leading side of each detent  54 . The inner periphery of metal washer  48 , i.e., the part of said metal washer that borders its central aperture, bears against the leading side of said detents, i.e., extends into each recess  55 , and therefore prevents trailing-to-leading displacement of spring holder  32  by piston biasing means  42 . 
     Spring holder  32  is preferably made of a metallic material that exhibits flexibility and resilience. Accordingly, radially inward travel of legs  52  disengages detents  54  from the inner peripheral edge of washer  48 , thereby allowing piston biasing means  42  to unload and to drive piston  18  and hence cannula  22  in a trailing-to-leading direction as denoted by arrow  20  as aforesaid, thereby administering liquid medicament  16  to the tissue of the user. 
     When auto injector  10  is not in use, such radially inward travel of legs  52  is barred by safety pin  56  that extends into the space surrounded by legs  52 . Safety pin  56  is formed integrally with cap  58  and is coincident with the longitudinal axis of symmetry of automatic injector  10 . 
     In this embodiment, outer gun sleeve  60  is a cap-like member of truncate configuration having an unnumbered central aperture formed therein to accommodate safety pin  56 . Clearance space  62  at the leading end of outer gun sleeve  60  and the trailing end of cartridge holder sleeve  12  enables displacement of outer gun sleeve  60  in the direction of arrow  20  when cap  58  is removed. 
     Leading end of truncate outer gun sleeve  60  has an annular, radially-inwardly turned detent  61  formed therein that is positioned on the leading side of the annular radially-outwardly turned detent  47  formed in inner gun sleeve  44  to interlock said inner and outer gun sleeves. 
     As will become more clear as this disclosure proceeds, truncate outer gun sleeve  60  may also take the form of an elongate outer gun sleeve  60   a , denoted in phantom lines in FIG.  2 . In that structural variation, outer gun sleeve  60  does not end at clearance space  62  but instead turns radially outwardly and partially ensleeves cartridge holder sleeve  12 . Outer gun sleeve  60   a  could extend nearly to shoulder  17 , but in a preferred embodiment, as depicted, it stops short of said shoulder to enhance the visibility of liquid medicament  16 , i.e., a user may inspect said medicament without looking through said outer gun sleeve  60   a.    
     A bead or protrusion is formed in surrounding relation to the central aperture formed in outer gun sleeve  60 , on the leading side of said central aperture, and an annular beveled surface  64  is formed in said bead or protrusion. Note in FIG. 2 that said annular beveled surface abuts against the respective beveled surfaces of detents  54  formed in the trailing end of spring holder  32 , and that beveled surfaces  54  and  64  are slidingly engaged to one another. Accordingly, when a user&#39;s thumb presses on outer gun sleeve  60  in the direction of arrow  20 , detent  64  drives detents  54  radially inwardly toward one another. Leading surface  54   a  (FIG. 3) of each detent  54  is thus displaced radially inwardly until each of said leading surfaces disengage from washer  48 . Such disengagement allows piston biasing means  42  to unload and piston  18 , cartridge  14 , and cannula  22  are driven in the direction of arrow  20 , thereby administering liquid medicament  16  to the user&#39;s tissue through cannula  22 . 
     Circumferentially spaced apart cartridge stops  66  extend radially inwardly into the lumen of cartridge holder sleeve  12  and perform the function their name expresses when piston biasing means  42  unloads. Cannula  22  pierces distal end  28  of sheath  26  when piston biasing means  42  unloads, but sheath  26  serves to cushion the impact of cartridge  14  as it is abruptly displaced in a trailing-to-leading direction. 
     Cartridge stops  66  are not a critical feature of the invention and may be eliminated by reducing the diameter of lumen  13  of cartridge holder sleeve  12  at the location of said cartridge stops  66 . More particularly, a lumen-diameter-reducing shoulder would be formed in lumen  13  at the trailing end of said stops  66 . 
     Turning now to FIGS. 5-8, wherein a second embodiment of the invention is disclosed, it will there be seen that the novel manually-operated sharps protector of this embodiment is denoted  70  as a whole. It is generally cylindrical in configuration and has a diameter-reducing frusto-conical leading end  72 . 
     An annular, radially inwardly extending detent  74  is formed in the trailing end of sharps protector  70 . When in its retracted, undeployed configuration, as depicted in FIG. 5, annular detent  74  is engaged with first annular recess  76  (depicted in FIG.  5  and numbered in FIG. 7) formed in cartridge holder sleeve  12 . When in its extended, deployed configuration, as depicted in FIG. 7, annular detent  74  is engaged with second annular recess  77  (depicted in FIG.  7  and numbered in FIG.  5 ), said second annular recess  77  being formed in cartridge holder sleeve  12  closer to its leading end than first annular recess  76 . Displacement of sharps protector  70  from the FIG. 5 position to the FIG. 7 position is performed manually. 
     Sheath  26  is depicted in its in-repose configuration in FIG.  5  and in its compressed configuration in FIG. 7, indicating that in FIG. 7 piston biasing means  42  is in its unloaded configuration and that cannula  22  is in its extended position. 
     FIG. 8 depicts a variation of the second embodiment where truncate outer gun sleeve  60  (FIG. 2) is replaced by elongate outer gun sleeve  60   a . As best understood in connection with FIG. 2, elongate outer gun sleeve  60   a  is disposed in housing relation to cartridge holder sleeve  12 , stopping on the trailing side of shoulder  17 . The provision of elongate outer gun sleeve eliminates annular radially outwardly turned detent  47  formed in inner gun sleeve  44  near its trailing end as depicted in FIG.  2  and also eliminates annular radially inwardly turned detent  61  formed in truncate outer gun sleeve  60  that interlocks with said detent  47  as depicted in FIG.  2 . Note that elongate gun sleeve  60   a  is sufficiently short so as not to cover the leading end of medicament-containing ampoule or cartridge  14 , thereby enhancing pre-firing inspection of said medicament. 
     Annular radially outwardly disposed detent  47  is re-located as depicted in FIG. 8 to the leading end of cartridge holder sleeve  12 , on the trailing side of shoulder  17 . 
     Annular recess  63  is formed on an internal surface of elongate outer gun sleeve  60   a  to receive said annular detent  47 . As illustrated, annular recess  63  has a longitudinal extent sufficient to accommodate detent  47  and to allow longitudinal displacement of said elongate outer gun sleeve  60   a  relative to cartridge holder sleeve  12  when said elongate outer gun sleeve is displaced in a trailing-to-leading direction to release piston biasing means  42 . Detent  47  abuts the leading end of recess  63  when piston biasing means  42  is loaded and the trailing end of said recess when said piston biasing means is unloaded. 
     The relocation of detent means  47  and the elimination of detent means  61 , as best understood by comparing FIGS. 2 and 8, simplifies the structure of the novel auto injector. Moreover, it enables a user to circumferentially grasp elongate outer gun sleeve  60   a  with a hand and to drive leading end  12   a  of cartridge holder sleeve  12  onto a target injection site, just as is done with the aforementioned EpiPen® auto injector of the prior art. Significantly, since the leading end of elongate outer gun sleeve  60   a  does not extent past shoulder  17 , said elongate outer gun sleeve does not infringe upon the space provided on the leading side of said shoulder to accommodate sharps protector  70  or  80 . 
     In the third embodiment of the invention, depicted in FIGS. 9-13, an internally mounted sharps protector biasing means, preferably in the form of coil spring  78 , is employed to deploy a second embodiment of the sharps protector, denoted  80 . 
     A second diameter-reducing shoulder  19  is formed in said cartridge holder sleeve in leading relation to first diameter-reducing shoulder  17 . A diameter-reducing taper  19   a  is formed in cartridge holder sleeve  12  in leading relation to diameter-reducing shoulder  19 . Diameter-reducing taper  19   a  forms a tapered section of said cartridge holder sleeve. Sharps protector biasing means  78  has a lumen that receives said tapered section therein. Sharps protector biasing means  78  has a trailing end that abuts diameter-reducing shoulder  19  and has a leading end that abuts the leading end of sharps protector  80 . 
     As best understood in connection with FIGS. 9-13, four sets of slot-shaped openings or catch means are formed in reduced diameter section  15  of cartridge holder sleeve  12 . First catch means  82  and accommodation slot  84  are separated from one another by annular part  15   a  of section  15 . Accommodation slot  84  is formed in section  15  in leading relation to first catch means  82  and second catch means  92  is formed in section  15  in leading relation to accommodation slot  84 . Guide slot  86  is formed in section  15  in circumferentially spaced relation to first catch means  82 , accommodation slot  84 , and second catch means  92 . 
     As perhaps best understood in connection with FIG. 17, first catch means  82  is provided in the form of two first catch members  82 ,  82  that are positioned in diametric opposition to one another. Moreover, there are two accommodations slots  84 ,  84  in diametric opposition to one another. Second catch means  92  is provided in the form of two second catch members  92 ,  92  that are positioned in diametric opposition to one another, and there are two guide slots  86 ,  86  in diametric opposition to one another. 
     A pair of diametrically opposed, radially inwardly projecting detents  87 ,  87 , best depicted in FIG. 17, is formed integrally with the trailing end of sharps protector  80  and respectively slideably engage elongate guide slots  86 ,  86 . More particularly, detents  87 ,  87  abut the respective trailing ends of guide slots  86 ,  86  when sharps protector biasing means  78  is under compression and sharps protector  80  is in its retracted position as depicted in FIGS. 9 and 11. 
     Detents  87 ,  87  abut the leading end of guide slots  86 ,  86  when sharps protector biasing means  78  is in repose and sharps protector  80  is in its fully extended, deployed configuration as depicted in FIG.  13 . 
     As best understood in connection with FIGS. 9 and 17, each latch means  88 ,  88  is punched out of sharps protector  80  so that a trailing end  89 ,  89  thereof remains secured to said sharps protector and forms a living hinge therewith. More particularly, each latch means  88 ,  88  is cut away from sharps protector  80  along a transverse parting line at its leading end, by a longitudinal parting line at each of its opposite sides, and remains connected to said sharps protector along said transversely disposed living hinge at its trailing end. 
     Leading end  88   a  of each latch means  88  is positioned in abutting relation to the leading end of first catch means  82  as depicted in FIG. 9 when sharps protector biasing means  78  is under compression and sharps protector  80  is in its retracted, undeployed configuration. 
     As depicted in FIG. 11, leading end  88   a  of each latch means  88  is disengaged from the leading end of its associated catch means  82  but sharps protector biasing means  78  has not unloaded because leading end  12   a  of cartridge holder sleeve  12  is disposed in abutting relation with a user&#39;s tissue  100 , thereby preventing unloading of sharps protector biasing means  78  even though the trailing end of sharps protector  80  is no longer retained by latch means  88 ,  88 . 
     As depicted in FIG. 13, cannula  22  has been withdrawn from tissue  100 , thereby allowing sharps protector biasing means  78  to unload and push sharps protector  80  into its fully extended, deployed position. 
     A pair of stop means  90 ,  90  is also punched out of said sharps protector  80 , each stop means  90  having a leading end  91  secured to said sharps protector to form a living hinge therewith. Each stop means  90  is biased to bend radially inwardly so that its trailing end abuts the trailing end of its associated accommodation slot  84  when sharps protector biasing means  78  is under load and sharps protector  80  is in its retracted, undeployed position. 
     As best understood by comparing FIGS. 9 and 11 with FIG. 13, each stop means  90  exits its associated accommodation slot  84  when sharps protector biasing means  78  unloads. However, since it is biased radially inwardly as aforesaid, each stop means  90  slides along the exterior surface  15  of the reduced diameter section of cartridge holder sleeve  12  until it encounters second catch means  92 . The trailing end of each stop means  90 , under its inherent bias, displaces radially inwardly to engage the trailing end of each second catch means  92  as depicted in FIG.  13 . 
     As depicted in FIG. 13, pressure applied to the leading end of sharps protector  80  in the direction of arrow  20   a  will not cause displacement of said sharps protector in the direction of said arrow  20   a  because the trailing end of each stop means  90  is disposed in abutting relation to the trailing shoulder of its associated second catch means  92 . This ensures that upon deployment of sharps protector  80 , it cannot be driven in a leading-to-trailing direction by pressure applied in said direction. 
     When cartridge  14  is propelled in the direction of arrow  20  by the means disclosed hereinabove, said cartridge contacts and displaces each latch means  88 ,  88  from its FIG. 9 position to its FIG. 11 position, i.e., it pushes said latch means radially outwardly. Accordingly, leading end  88   a  of each latch means  88 ,  88  disengages from section  15   a  of cartridge holder reduced diameter section  15 , i.e., disengages from the leading end of first catch means  82 , thereby freeing sharps protector biasing means  78  to unload. 
     Ramp  93  (FIG. 17) is provided to facilitate the initial assembly of automatic injector  10 . Radially inwardly biased stop means  90  is aligned with ramp  93  when sharps protector  80  is mounted onto the leading end of cartridge sleeve holder  12  during assembly so that said radially-inwardly biased stop means  90  slides up said ramp  93  onto surface  15  which is the reduced diameter part of cartridge sleeve holder  12  that is in leading relation to shoulder  17  as aforementioned. Sharps protector  80  is then rotated about its longitudinal axis of symmetry until detents  87 ,  87  enter into engagement with guide slots  86 ,  86 , latch means  88 ,  88  enters into engagement with first catch means  82 ,  82 , and stop means  90 ,  90  enter into engagement with accommodation slots  84 ,  84 . 
     The fourth embodiment of the invention is depicted in FIGS. 14-16. The embodiment of FIGS. 14-16 differs from the preceding embodiment of FIGS. 9-13 in that sharps protector biasing means  78   a  is mounted externally of sharps protector  80 . Specifically, sharps protector biasing means  78   a  has a leading end disposed in abutting relation to a trailing end of sharps protector  80  and a trailing end in abutting relation to shoulder  17 . 
     As indicated by comparing FIG.  15  and FIG. 16 to one another, spring  78   a  may be substantially covered when a longer version of elongate outer gun sleeve  60   a  is employed (FIG. 15, with elongate gun sleeve  60   a  in phantom lines) and may be uncovered when a shortened version of elongate outer gun sleeve  60   a  is provided (FIG. 16, with elongate outer gun sleeve  60   a  depicted in longitudinal section). The purpose of the shortened version of elongate outer gun sleeve  60   a  , as mentioned earlier, is to enhance the pre-firing visual inspection of the medicament contained within ampoule or cartridge  14 . 
     Sharps protector biasing means  78   a  of this embodiment is triggered in substantially the same way as sharps protector biasing means  78  of the internally-mounted spring embodiment. 
     In the embodiment of FIG. 16, annular radially outwardly extending detent  47  is formed in cylinder holder sleeve  12  near the leading end thereof. Annular recess  63  formed in the interior cylindrical wall of cartridge holder sleeve  12  receives said detent  47  just as in the preceding embodiment. 
     The ability to release piston biasing means  42  by pressing on outer gun sleeve  60  after removing safety cap  58  is made possible by eliminating the outer cylindrical sleeve of the prior art automatic injector. The ability to release piston biasing means  42  after first positioning leading end  12   a  of cartridge holder sleeve  12  on an injection target site is also made possible by said improvement. Elimination of such outer cylindrical sleeve saves a substantial amount of materials and further enables the provision of an elongate reduced diameter section  15  of cylindrical sleeve holder  12  that provides ample mounting space for a sharps protector. The new design also greatly reduces the longitudinal extent of the outer gun sleeve, thereby further saving materials and enhancing pre-firing inspection of medicament by eliminating a layer of plastic to look through. The provision of a manually deployed or an automatically deployed sharps protector for an automatic injector, made possible by said improvements, also represents a significant advance in the art. 
     Moreover, where an outer gun sleeve is lengthened to enable circumferential grasping of the device, a shortened version of said elongated outer gun sleeve enhances pre-firing medicament inspection. 
     It will thus be seen that the objects set forth above, and those made apparent from the foregoing description, are efficiently attained. Since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween. 
     Now that the invention has been described,