Abstract:
An auto-injection device is provided for mounting a standard medical syringe which enables the user to automatically inject the contents of the syringe to a desired penetration depth. The auto-injection device includes a barrel sized for receiving the syringe therein, a driver shiftably received in the barrel for moving the syringe and causing injection of its contents, and a trigger accessible from outside the syringe, the trigger requiring movement across the exterior surface of the barrel prior to depression for releasing the plunger as a safety against inadvertent needle exposure and discharge. The barrel may include a window for enabling the user to ascertain whether the device is cocked or not. The barrel may be provided in two separate sections with one of the sections receivable into the other to permit cocking. The barrel also may include a slot for receiving a button to permit exposure of the needle to remove a protective cap when the device is cocked and the syringe is withdrawn into the barrel.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention broadly concerns an device for permitting users to self-inject a medication in a conventional syringe to a preselected depth of penetration by using a simplified triggering mechanism device permitting controlled dosing. More particularly, the present invention is concerned with an automatic injection device with a triggering mechanism which is simple for geriatric users yet includes a safety feature inhibiting premature needle projection and medication discharge. 
     2. Description of the Prior Art 
     Auto-injection devices as described herein are used by an individual to self-administer a liquid medication through a needle subcutaneously. These devices help an individual to administer the medication by pushing or driving the needle through the skin and then expressing a dosage of the medication. It can be appreciated that such devices help alleviate the fear associated with injecting oneself and provide a convenience in regard to the accuracy of the dosing. 
     To this end, a number of different auto-injection devices have been developed. These include the devices shown in U.S. Pat. Nos. 5,137,516 and 5,425,715. These devices provide for an injection from a medication received in an ampule or cartridge assembly. Typically, such devices are first cocked, positioned, and then triggered to administer a desired quantity of medication. The &#39;516 patent operates by actuation of a trigger in combination with movement of two separate parts to prevent accidental actuation. However, both of these devices use a preloaded cartridge or ampule and are not readily adaptable to use with a conventional syringe. This has certain disadvantages in the types of medication which can be obtained and dispensed, as the cartridges or ampules cannot be locally filled by a pharmacist and are not adapted for receiving a commonly available syringe. 
     Another auto-injection device which can be used with a commercially available cartridge or syringe is shown in U.S. Pat. No. 5,358,489. This device is useful for administering medication but is difficult to handle and use, as a separate tool such as a screwdriver must be employed for recocking and a protective cap may not be retained on the tip of the needle until the desired moment of use. Thus, the &#39;489 device is not well equipped for storage in a ready to use condition for treatment of male impotence by injection or other therapies requiring simplicity of operation and convenience of storage. 
     It is generally preferable to refrain from “re-capping” a syringe after an injection has been administered because there remains some risk of cross-contamination if the user&#39;s hand slips and their finger is stuck by the needle. However, replacement of the cap in self-injection devices may be desired where there are inadequate facilities for safe storage of medical sharps, or where the syringe might be set aside for some time, with the result that the user may forget that the needle is exposed. 
     There has thus developed a need for an auto-injection device capable of use with a standard syringe which can be filled by a local pharmacist and which can be stored with the cap in place to inhibit undesired needle “sticks”. 
     There has also developed a need for an auto-injection device which is easy to use by geriatric patients and yet resists undesired or premature needle exposure and medication expression. 
     There has further developed a need for an auto-injection device which can be partially disassembled for loading and cocked, all without the need for additional tools. 
     There is a further need for an auto-injection device which has a trigger which is readily accessible, yet is safe to use and has a simple and inexpensive construction. 
     There is an additional need for an auto-injection device which includes a feature to enhance safe replacement of a needle on the syringe contained therein. 
     SUMMARY OF THE INVENTION 
     These needs are largely met by the auto-injection device of the present invention which is adapted to receive a conventional syringe with the needle cap in place both during loading and up until administration. The device hereof is easy to use and includes a unique trigger which requires displacement along two axes in order to actuate the injection sequence. 
     The invention hereof broadly includes a body or barrel presenting an internal cavity for receiving a syringe therein. The barrel cavity presents a longitudinal axis adapted for receiving a syringe therein. The barrel presents an open front end for positioning against a patient&#39;s body and through which the needle of the syringe may project, and a rear end. A driver is positioned within the barrel for longitudinal shifting within the cavity, the driver being configured to carry a conventional syringe. The driver includes a catch at the rearward end thereof adapted to engage a release mounted on the barrel. The release includes a resilient member for biasing the release to a position engaged with the catch on the driver. The release is configured and mounted on the barrel to require movement of the release along the surface of the barrel as well as depression into the cavity in order to disengage from the catch and release the driver for injecting the contents of the syringe. 
     Advantageously, the auto-injection device hereof has a barrel separable into two separate sections. The driver is also provided in two components, including a syringe receiver mounted in the forward section of the barrel and a pusher positioned in the normally rearward section of the barrel. The two sections of the barrel are complementally configured to permit an elongated neck on the forward section to enter the cavity of the rearward section to thereby urge the pusher rearwardly until the catch on the pusher engages the release. The syringe receiver is provided with a plurality of inwardly directed fingers which hold the syringe in a central, longitudinally aligned position, but permit insertion and withdrawal of the syringe with the syringe cap retained thereon. The syringe receiver is also provided with a button which projects into a slot in the barrel to permit manual shifting of the syringe to remove or replace the cap on the syringe. The slot includes a recess which holds the button and thus the syringe in a retracted position within the cavity of the barrel. 
     A spring is provided to push the driver forwardly when released after cocking. A second spring, of a lesser spring force, is provided to urge the syringe receiver rearwardly into a position normally placing the tip of the syringe needle rearwardly of the front end of the barrel when the device is uncocked. 
     The release is preferably provided with a trigger which extends radially outwardly of the exterior surface of the barrel. The trigger is preferably integral with a resilient arm which biases the trigger outwardly, and also includes a resilient stem for biasing the trigger to a position opposite the exterior surface of the barrel and out of alignment with a trigger access. The release further includes a notch in which the catch of the driver is received when the device is cocked. In order to actuate the device and move the syringe forwardly within the cavity, the user must push the trigger along the surface of the barrel and then through the trigger access to overcome the resilient arm and move the notch to release the catch. Preferably, indicia is provided on the driver which is visible through a window defined in the barrel, whereby the user can identify when the device is cocked. 
     As so configured, the auto-injection device hereof is particularly easy to use. By separating the threaded connectors on the two barrel sections, a conventional syringe may be inserted into the syringe receiver with its needle or cannula pointing forwardly and its plunger extending rearwardly. The neck of the forward section is then inserted into the cavity of the rearward section and the pusher of the driver urged rearwardly until the catch is held in the notch of the release. The forward section is then threaded on the rearward section and may be stored until use is desired. In order to inject the medication in the syringe, the user pushes the button forwardly along the slot, which extends the needle and cap into a position whereby the user may manually remove the cap. The second spring then moves the needle back within the cavity. 
     Administering the injection is accomplished after the front end is placed on the desired injection site. The user is inhibited from inadvertently triggering the device by the two-direction movement of the trigger necessary to release the driver. Once the trigger is moved along the exterior surface of the barrel until it is over the access opening, it may be depressed to move the notch and release the catch on the pusher. The pusher then moves forwardly against the thumbutton of the syringe plunger, moving the syringe forwardly and pushing the cannula under the skin of the patient until the syringe is stopped from further movement within the cavity. After syringe movement is stopped, the pusher continues its forward movement, overcoming the resistance of the liquid medication in the syringe to express the medication from the cannula. Once the medication is injected into the patient, the needle is withdrawn and the cap replaced on the needle with the syringe receiver shifted rearwardly and the button thereon held in the recess. 
     It may be readily appreciated that the device hereof permits a simplified injection procedure with safeguards against undesired actuation of the mechanism in a simple, inexpensive device using conventional syringes. Thus, the device hereof presents significant advantages over more complicated auto-injection devices requiring specialized cartridges, additional tools, or which risk premature needle exposure. 
     These and other benefits of the present invention will be readily evident to those skilled in the art with reference to the drawing and detailed description set forth below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the auto-injection device hereof showing the device in the uncocked position carrying a syringe with the needle cap projecting from the front end of the device; 
     FIG. 2 is a vertical cross-sectional view similar to FIG. 1, showing the syringe within the barrel of the device and the driver in the cocked position; 
     FIG. 3 is a vertical cross-sectional view of the device hereof showing the first front section and second rear section of the barrel separated with the syringe carried by the syringe receiver of the driver; and 
     FIG. 4 is an enlarged vertical end elevational view of the device hereof taken rearwardly of the release facing toward the front of the device with the end cap removed, showing the catch of the pusher held in the notch of the release. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawing, an auto-injection device  10  showing the preferred embodiment of the present invention broadly includes a barrel  12  presenting a longitudinally extending cavity  14 . A driver  16  and a syringe  18  are received in the cavity  14 , the barrel mounting a release  20  for actuating the device  10  to inject a liquid medication from the syringe  18 . 
     In greater detail, the syringe  18  is of conventional construction and is commercially available from a variety of sources, such as, for example, a 1 cc syringe offered by Becton-Dickenson. The syringe includes a body  22  mounting a needle  24  and receiving a plunger  26 . The needle  24  includes a needle hub  28  and a cannula  30  for penetrating the skin and injecting the liquid medication contained in the syringe body  22 . Such medication may include, for example, insulin for treating diabetes, a vasodilator for treating male sexual dysfunction, or other liquids as desired. The needle cannula receives thereon a cap  32  which extends over the cannula  30  and is removably mounted on the needle hub  28 . The plunger  26  includes a shaft  34  presenting a stopper at one end thereof and received within the body  22 , and a driving surface  36  at the rear end, the driving surface  36  normally used as a thumb rest. The body  22  is tubular and may present scale markings on the surface thereof to indicate the volume of liquid in the syringe. A finger flange  38  extends laterally from the rear end of the body  22 . 
     The barrel  12  includes a first front section  40  and a second rear section  42  which are longitudinally aligned along a longitudinal axis A when threadably interconnected as shown in FIG. 1, and separable into two sections as shown in FIG.  3 . The rear section  42  includes a threaded insert  44  and the front section  40  presents a threaded sleeve  46  at its rear end for receiving the threaded insert  44 . The front section  40  also presents a front end  48  which is open and has a diameter sufficient to permit the passage of the cap  32  on the needle  24  to pass therethrough. The front section  40  also has a neck  50  which extends rearwardly from the front end  48  and is sufficiently narrow to allow insertion of the neck  50  into the cavity  14  of the rear section  42 . A collar  52  is positioned rearwardly of neck  50  on the front section  40 , the collar  52  presenting an enlarged internal diameter relative to the internal diameter of the neck  50 , and having a rim  54  where the diameter of the cavity  14  internally of the collar  52  narrows to the diameter of the neck  50 . The internal diameter of the cavity  14  interiorly of the neck  50  further narrows at edge  56  located between front end  48  and rim  54 . A longitudinally extending slot  58  is provided through the front section  40 , the slot  58  communicating with a laterally displaced recess  59 . 
     The rear section  42  presents a rear end  60  mounting a endcap  62  thereon. A window  64  is provided in the rear section  42  for viewing into the cavity  14 . A trigger access  66  is defined at the rear end of the barrel  12  just forwardly of endcap  62 . The endcap  62  may be snap-fitted onto the rear end  60  of the rear section or, more preferably, adhesively secured thereto. 
     The plunger  26  is axially shiftable along the longitudinal axis A within the cavity  14  and includes a pusher  68  shiftably located in the rear section  42  and a syringe receiver  70  shiftably located in the front section  40 . The pusher includes a base  72  and a cylindrical wall  74  having a diameter preferably sufficient to receive the driving surface  36  of the syringe plunger  26  therein. A stem  76  projects rearwardly from base  72  and terminates in a frustoconically shaped catch  78  having a margin  80 . The wall  74  extends both forwardly and rearwardly from base  72  as illustrated in FIG.  2 . The pusher  68  includes indicia  82 , such as a colored band, which is visible through the window  64  when the pusher is shifted forwardly as shown in FIG.  3 . When shifted forwardly, a circumferentially extending lug  84  on the pusher  68  engages an internal rim  86  inward of the threaded insert  44  to limit forward travel of the pusher  68 . 
     The syringe receiver  70  is not only longitudinally shiftably received in the cavity  14  but may also be shifted circumferentially relative to barrel  12 . The syringe receiver  70  includes a plurality of circumferentially arrayed flexible alignment fingers  88  which collectively engage and center the body  22  of syringe  18 . The rearward end of the syringe receiver  70  presents a breech  90  including a margin  92  against which finger flanges  38  of the syringe  18  engage. The syringe receiver further presents an outwardly extending button  94  which projects into and is longitudinally slidably received within slot  58 , and may be circumferentially shifted into the recess  59 . Recess  59  is configured and sized to receive button  94 , and then to hold button  94  against undesired lateral shifting when button  94  is biased forwardly. The forward end of the syringe receiver  70  presents a circular edge  96 . 
     Release  20  is best seen in FIG.  4  and includes a frame  98  having a v-shaped notch  100  centrally located therein. The frame includes a pair of legs  102  and  104  on either side of the notch  100  and a bridge  106  connecting the legs  102 ,  104 . A resilient arm  108  is located opposite the bridge  106  and biases the release  20  located within the cavity  14  of the rear section  42  toward the trigger access  66 . The arm  108  is flexible and cantilevered from the main frame  98  presenting a gap  109  therebetween. Trigger  110  extends through the trigger access  66  and presents an enlarged head  112  having a chin  114  projecting circumferentially along the exterior surface  116  of wall  39  of the barrel  12 . A resilient reed  118  is located on the opposite side of trigger  110  from chin  114  and also extends into trigger access  66  and biases the trigger  110  to a position as shown in FIG. 4 whereby the chin  114  will engage the exterior surface  116  of the barrel and not pass through the trigger access  66  when the head  112  is only depressed and not first pushed toward reed  118 . 
     The auto-injector device hereof includes a first spring  120  positioned in the cavity  14  of the rear section  42  between the driver  16  and the release  20 . The spring  120  is preferably a coil spring which is helically arrayed around the stem  76  of the pusher  68  and extends forwardly to engage base  72  as shown in FIG.  2  and is received within wall  74  when the pusher is in its rearward position. A second spring  122  is located in the cavity  14  between the syringe receiver  70  and the edge  56  on barrel  12  as shown in FIG.  3 . Second spring  122  is of a lesser spring coefficient than first spring  120 , so that when first and second sections are assembled and the first spring  120  is unloaded and pushing against pusher  68  and syringe  18 , the second spring  122  yields and compresses. Second spring  122  is held in position by an alignment member  126  positioned forwardly of release  20 . 
     To use the device  10 , the user first unscrews the first front section  40  from the second, rear section  42  and inserts the neck  50  into the cavity  14  of the rear section. The front end  48  then engages the pusher  68  and moves it rearwardly against first spring  120  until the catch  78  is received in notch  100 . With the catch  78  engaged in the notch  100 , the pusher  68  compresses and loads first spring  120  to the position shown in FIG. 2. A syringe  18  is then inserted into the syringe receiver  70  until the finger flanges  38  engage the breech  90  of the syringe receiver  70 . With the syringe thus loaded into the receiver  70 , the second spring  122  biases the syringe receiver  70  rearwardly so that the cap  32  and the tip of the cannula  30  is located within the cavity  14  and rearwardly of the front end  48 . The front section  40  is then threaded onto the rear section  42  and the device is ready for use. When ready for use, the indicia  82  is not visible in window  64 . 
     When it is desired to administer a dosage of medication contained within the body  22  of the syringe  18 , the user first selects the desired location on the skin for positioning of the front end  48  of the barrel  12 . The cap  32  is then removed from the syringe  18  by shifting the button  94  along the slot  58  to compress the second spring  122  and move the syringe receiver  70  and syringe  18  forwardly a sufficient difference to permit manual removal of the cap  32  as illustrated in FIG.  1 . After the cap  32  has been removed, the button  94  is released and permitted to slide rearwardly, carrying with it the syringe receiver  70 . The front end  48  is then placed on the desired target location of the patient&#39;s skin. To administer the injection, the user must first shift the head  112  of the trigger  110  toward the reed  118  in a generally circumferential direction as illustrated by the arrow in FIG.  4 . This permits the chin  114  on the head  112  to clear the exterior surface  116  of the barrel  12  and lie directly over the trigger access  66 . This required lateral movement inhibits undesired or premature actuation of the device  10 . After this lateral shifting, the trigger  110  is then depressed in the direction of the second arrow in FIG. 4 to overcome the resistance of resilient arm  108 . When the trigger  110  is thus depressed, the v-shaped notch shifts as shown in phantom in FIG. 4 to permit the margin  80  thereon to clear the legs  102  and  104  of the release  20 . Once the catch  78  clears the arms and is permitted to move forwardly through notch  100 , the first spring moves the pusher  68  forwardly whereby base  72  engages the driving surface  36  on the plunger  26  of the syringe. 
     The initial resistance of the stopper within the body  22  of the syringe  18  and the fluid resistance of the medication is greater than the spring coefficient of the second spring  122 . Thus, the syringe  18  and the syringe receiver  70  move forwardly and compress the second spring  122  in response to forward movement of the pusher  68 . The forward movement of the syringe  18  and syringe receiver  70  continue as the cannula  30  penetrates the patient&#39;s skin until the syringe receiver  70  is fully shifted forward to compress the second spring  122 . Before the pusher  68  is fully forward as illustrated in FIG. 3, the second spring  122  will be fully compressed and the cannula  30  will have penetrated to the predetermined, desired subcutaneous depth. The pusher  68  then continues to its fully forward position as the base  72  pushes against the driving surface  36  and shifts the plunger  26  relative to the syringe body  22  to express the medication from the syringe. Thereafter, the patient withdraws the needle  24  and replaces the cap  32  as illustrated in FIG.  1 . To replace the cap  32 , the patient preferably moves the button  94  rearwardly and moves the button  94  laterally into recess  59 . A nib  124  partially separates the recess  59  from the slot  58 , so that when second spring  122  pushes against the syringe receiver  70 , the button  94  is held against further forward movement and inhibited from undesired rotational movement into the slot  58 . This cause the cannula  30  to be withdrawn into the cavity  14  and rearward of front end  48  while the cap  32  is manually replaced on the syringe. The button  94  can be safely shifted back into the slot  58  after the cap is replaced so that the cap  32  will be in the position shown in FIG.  1 . 
     FIG. 1 illustrates the condition of the device  10  hereof in a discharged position where upon the patient can see the indicia  32  through the window  64 . The needle cannula  30  is also illustrated in FIG. 1 to show its position extending beyond the front end  48  of barrel  12 . The syringe  18  may be disposed by unscrewing the front and rear sections  40 ,  42  and withdrawing the syringe rearwardly through the syringe receiver  70  from the front section  40  of the barrel  12 . 
     Although preferred forms of the invention have been described above, it is to be recognized that such disclosure is by way of illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention. 
     The inventor hereby states his intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of his invention as it pertains to any apparatus not materially departing from but outside the liberal scope of the invention as set out in the following claims.