Patent Description:
The advantages of needle-free injection devices have been recognized for some time. Some of the advantages of needle-free devices and methods include the absence of a needle which can intimidate a patient and also present a hazard to healthcare workers. In addition, injection using a needle may increase the risk of cross-contamination between patients. Furthermore, with an injection device that employs a needle there is substantial risk of needle breakage in the tissue of a human or animal patient. The injection jet generated by a needle-free device is generally smaller in diameter than a hypodermic needle and thus in certain instances a needle-free injection is less painful than an injection provided by a hypodermic needle device.

Because of these and other advantages of needle-free injection many variations of pneumatic, electronic or spring activated needle-free injection devices have been designed to provide a single injection, or alternatively a series of injections to one or more patients. Most known needle-free injection devices operate by driving the injectable fluid through a fine nozzle with a powered piston to create a fine but high pressure jet of fluid that penetrates the skin. Needle-free injection devices are not inherently risk free. For example, it is possible if precautions are not taken, to cause a laceration as opposed to a proper injection with a needle-free device. In addition, it is critical to design a needle-free device with safety features substantially minimizing the risk of inadvertent triggering or injection.

Safety issues may involve the risk of accidental discharge of a needle-free device. Safety issue can become acute in association with devices that have exposed triggers or devices which include a ram or piston driving mechanism that can extend beyond the housing of the injector. The risk of using these types of devices is similar to the risks associated with the triggers on firearms. Thus, the inadvertent pressing of an exposed and armed trigger can cause the accidental or premature firing or triggering of the needle-free injection device.

One class of reliability issue with known needle-free injection devices involves difficulty delivering an entire preselected dosage of injectable liquid into the appropriate tissue of a patient. This situation can be exacerbated when the dosage is intended to be delivered shallowly, in the intradermal space for example. Dosage reliability issues have a broad spectrum of causes. One significant underlying cause is the difficulty encountered in the creation of a suitable jet or stream of fluid and introduction of this jet into or through the skin of a patient. Preferably, the jet will be a very fine jet that will impact a section of taught skin with much of the energy of the stream being used to penetrate the skin. The elasticity and permeability of a patient's skin can however vary with respect to other patients or across different locations on a patient's body. Another reliability issue concerns difficulty encountered efficiently and accurately pre-filling needle-free syringes to a selected dosage without significant waste of a potentially very limited supply of injectable fluid.

The embodiments disclosed herein are directed toward overcoming one or more of the problems discussed above.

The present invention refers to a needle-free injection device suitable for delivering a therapeutic substance into the intradermal space of a patient according to claim <NUM>. The needle-free injection device includes a compressible main spring which can be compressed to place the needle-free injection device into an armed configuration. In addition, the device includes at least one and possibly two handles which are attached to the needle-free injection device such that the handle or handles may pivot between an open and a closed position. In addition, the device includes a linkage between one or each of the handles and the main spring. The linkage provides for the mainspring to be compressed into the armed configuration when the device handle or handles are moved from the open to the closed position.

The disclosed embodiments therefore uniquely include one or more handles attached to the needle-free injection device which provide for the compression of the main spring. The leverage necessary to compress a main spring which is suitably sized to deliver a needle-free injection places substantial stress on the hinges connecting the handles to the device. Therefore, the needle-free injection device may also include pivot hinges having upper and lower pivot studs and spatially separated radius surfaces. In use, the upper pivot stud is engaged with the upper handle and the lower pivot stud is engaged with the lower handle. The separate radius surfaces mate with a corresponding or matching surface on the upper and lower handles and provide additional support to a handle beyond that provided by the pivot stud. Device longevity and proper functioning is it promoted by providing both pivot studs and radius surfaces to support each handle. Typically, each handle will be supported by left and right pivot studs and left and right radius surfaces on each side of the device.

Certain embodiments of the needle-free injection device also include a sleeve engaged with the handle linkages and the main spring, which sleeve is caused to move or slide laterally with respect to the portions of the injection device housing the mainspring when the handle or handles are moved from the open position to the closed position. In an embodiment having two handles, the handles made generally be referred to as an upper and lower handle and in selected embodiments the upper and lower handle each have at least one linkage between the respective handle and the sleeve or main spring.

Disclosed embodiments also include a catch mechanism configured to engage the handles and hold each in the closed position. Furthermore the device may include a release button or release mechanism configured to release the closed handles and allow each handle to move to the open position. As noted below, safe usage is enhanced if the release button cannot under any circumstance also release energy stored in the main spring.

The needle-free injection device includes an injector tube housing the main spring and a hammer. During an injection, force stored in the main spring may be released to drive the hammer forward or toward the nozzle end of the syringe. The hammer is thus in contact with the plunger of the needle-free syringe and positioned to transfer energy from the main spring to the plunger causing a needle-free injection.

In certain embodiments the injector tube housing the main spring, hammer and associated apparatus can be caused to move laterally away from the front (syringe) end of the device when pressure is applied to a needle-free syringe prior to an injection. The syringe itself is attached to the injector tube in use and moves with the main spring, hammer and associated apparatus. As described in detail below, the respective movement between the injector tube and other elements of the needle-free injection device provides certain specific functional and safety advantages.

In particular, the needle-free injection device may include a skin tensioning spring configured to bias the injector tube toward the syringe end of the injection device. The disclosed devices will include an actuation button which, when the device is ready to be operated to deliver an injection, will be in mechanical communication with a hammer release. The actuation button therefore, in certain carefully controlled circumstances, causes the device to deliver a needle-free injection. Safe and effective functioning of the device can be enhanced by configuring the actuation button such that it cannot engage the hammer release unless the injector tube moved to a position fully away from the front end of the device.

In embodiments including a skin tensioning spring, the rearward movement of the injector tube and associated apparatus prior to injection is important for two distinct reasons. First, prior to an injection, the nozzle end of a needle-free syringe is placed against a patient's skin and the needle-free injection device is pressed toward the patient with sufficient force to compress the skin tensioning spring. This action, in conjunction with the specific shape of the nozzle end, causes the patient's skin to be appropriately tensioned to assure that a suitable injection is made. In addition, providing an actuation button that does not engage the hammer release mechanism unless the injector tube is moved to a position fully away from the front end of the device assures that an injection cannot be delivered in normal use unless the nozzle end of the needle-free syringe is placed against a patient's skin and the needle-free injection device is pressed forward with sufficient force properly tension the skin.

The disclosed device embodiments may be implemented with any type or configuration of hammer and hammer release apparatus. One representative type of hammer release includes one or more ball bearings housed within a ball lock which communicates with a notch defined within the exterior surface of the hammer. As noted above, the handles of the device may be opened from a latched configuration after use to compress the main spring by operating a release switch or button. It is important for safe used to assure that the handle release cannot also or inadvertently release the main spring and hammer. The disclosed embodiments accomplish this requirement by including a separate hammer release apparatus which may only be actuated by the actuation switch and then only when the device is properly positioned for the delivery of an injection as noted above.

Additional safety may be provided by including a retract button mechanically linked to the injector tube. The retract button may be configured to cause the injector tube to be locked in the forward position, toward the syringe end of the device, unless the retract button is depressed or otherwise activated. Thus, a user is substantially prohibited from accidentally placing the device into an injection configuration since the injector tube cannot be moved away from the syringe end of the device into the injection configuration described above unless the user deliberately and intentionally permits said movement by operating the retract button before or while applying enough pressure to a patient's skin with the nozzle end of the syringe to compress the skin tensioning spring.

It is also described a needle-free injection system comprising a needle-free injection device substantially as described above. In addition a system will include at least one needle-free syringe. One disclosed needle-free syringe includes a syringe body having a nozzle at one end and a dose setting surface substantially opposite the nozzle. The syringe will also include a plunger body having a leading end, a seal and a hammer surface substantially opposite the leading end. In use, the plunger body is inserted into a dosage space defined with in the syringe such that the leading end of the plunger points toward the syringe nozzle. The dosage space is defined within the syringe between the nozzle opening and the plunger seal. A needle-free syringe may be sized and configured such that the dosage space has a select dosage volume when the plunger body is positioned within the syringe body and the dose setting surface and hammer surface of the plunger are coplanar. The needle-free syringe and plunger assembly may be provided to define any suitable dosage volume. For example, a dosage volume of <NUM> is suitable for the delivery of certain therapeutic substances into the intradermal space.

The needle-free syringe system may optionally further include a handle substantially opposite the plunger body, a separable shaft between the plunger body and the handle, and a break line defined in the separable shaft. In this alternative, the break line defines the hammer surface on the plunger body. In addition, the handle may include a plunger positioning surface which cooperates with the hammer surface to position the plunger body in a needle-free syringe body such that the dose setting surface and hammer surface are coplanar. The plunger positioning surface may define a hole providing a clearance for any nub formed in the hammer surface upon separation of the plunger body from the handle at the break line. Alternatively or in addition to the above, the end of the hammer operatively positioned adjacent to the plunger may cause the hammer surface and dose setting surface to become coplanar when a syringe is loaded into the armed device.

Alternative embodiments disclosed herein include methods of operating a needle-free injection device or system, to arm the device or perform other operations. For example the disclosed methods may be implemented to deliver an injection into the intradermal space of a patient, said methods not forming part of the invention. Disclosed methods include providing a needle-free injection device substantially as described above and moving the handle or handles from the open position to the closed position thereby compressing the device mainspring from an un-armed to an armed position. The method may further include loading a needle-free syringe into the device. Releasing the energy stored in the mainspring drives a syringe plunger forward causing an injection, said method not forming part of the present invention.

As noted above, selected embodiments of the disclosed devices include certain features which promote safe and effective operation. Accordingly, the disclosed methods may include the steps of activating a retract button to unlock an injector tube or similar apparatus, thus allowing the injector tube, syringe and associated apparatus to be moved with respect to other device elements. The method may further include applying force against a patient's skin at the nozzle end of the needle-free syringe thereby causing the injector tube to move laterally with respect to the handles or other stationary elements of the injector. As noted above, this step properly tensions the patient's skin for an injection and moves the actuation mechanism of the needle-free injector into an injection position. Then and only then, an actuation button may be activated to release the energy stored in the mainspring to drive the syringe plunger forward causing an injection.

Unless otherwise indicated, all numbers expressing quantities of ingredients, dimensions reaction conditions and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about".

In this application and the claims, the use of the singular includes the plural unless specifically stated otherwise. In addition, use of "or" means "and/or" unless stated otherwise. Moreover, the use of the term "including", as well as other forms, such as "includes" and "included", is not limiting. Also, terms such as "element" or "component" encompass both elements and components comprising one unit and elements and components that comprise more than one unit unless specifically stated otherwise.

<FIG> is an exploded perspective view of a needle-free injection device <NUM>. The needle-free injection device <NUM> includes an injection power source, in particular, a main spring <NUM> which may be compressed to store energy for subsequent release to power an injection. The main spring <NUM> is engaged with a hammer <NUM> such that when energy stored within the main spring <NUM> is released, the hammer <NUM> is driven toward and into contact with the plunger of a needle-free syringe providing for a needle-free injection as described in detail below. The main spring <NUM>, hammer <NUM> and associated apparatus may be housed within an injector tube <NUM>.

The needle-free injection device <NUM> also includes a core <NUM> which may alternatively be referred to as the injector device body. The core <NUM> may include, but is not limited to a pivot sleeve <NUM>. The needle-free injection device <NUM> also includes a return sleeve <NUM>, syringe receptacle <NUM> and latch and release sleeve <NUM>. The structure and functioning of each of these elements is described in detail below.

It may also be noted from <FIG> that the needle-free injection device <NUM> includes at least one handle, and in the illustrated embodiment, two handles, which may be referred to as an upper handle <NUM> and lower handle <NUM>. In the illustrated embodiment the handles <NUM>, <NUM> are attached to the pivot sleeve <NUM>. At least one handle associated with the injector device or alternatively both the upper handle <NUM> and lower handle <NUM> may be moved from an open position to a closed position by a user to provide the force necessary to compress, store energy and thereby arm the main spring <NUM> for an injection.

Also shown on <FIG> are three control buttons or switches associated with the device including an actuation button <NUM>, retract button <NUM> and release button <NUM>. Other operational buttons could be provided in alternative embodiments.

<FIG> show external side elevation views of the needle-free injection device <NUM> with the handles <NUM>, <NUM> and other elements in various operational states. In particular, <FIG> shows the handles <NUM>, <NUM> in the fully open position. In the <FIG> position the main spring <NUM> is extended or de-compressed and ready to be charged for an injection. <FIG> illustrates the handles <NUM>, <NUM> in a partially closed configuration, for example as the handles would be positioned during the process of compressing the main spring <NUM>, but prior to full compression. <FIG> shows the handles <NUM>, <NUM> fully closed and latched. In the <FIG> configuration the main spring <NUM> is fully charged and ready to provide for an injection as described in detail below. <FIG> illustrates the charged needle-free injection device <NUM> with a needle-free syringe <NUM> inserted into the syringe receptacle <NUM> at the syringe end <NUM> of the needle-free injection device <NUM>.

<FIG> show various cross-sectional views of the needle-free injection device <NUM> in selected operational states. <FIG> may thus be referred to in order to more fully understand the elements and operational subsystems providing enhanced convenience, safety, durability, and effectiveness to the user of a needle-free injection device <NUM>. In particular, <FIG> is a cross-sectional view of the needle-free injection device <NUM> with the handles <NUM>, <NUM> in a fully open position. As noted above, in the <FIG> or <FIG> position, the main spring <NUM> is in a decompressed and ready to charge state. As may be observed on <FIG>, each of the handles <NUM>, <NUM> engages with a linkage <NUM>, <NUM> respectively which in turn is engaged with the return sleeve <NUM>. In the embodiment illustrated in <FIG>, the upper handle <NUM> is engaged with an upper linkage <NUM> and the lower handle <NUM> is engaged with a lower linkage <NUM>. Both the upper and lower linkage <NUM>, <NUM> have a bearing surface which engages a corresponding surface on the return sleeve <NUM>. As may be noted by comparing <FIG> with <FIG> (which shows the handles <NUM>, <NUM> in a partially closed position) as the handles <NUM>, <NUM> are closed, the linkages <NUM>, <NUM> force the return sleeve <NUM> away from the syringe end <NUM> of the device. As the return sleeve <NUM> is forced toward the rear of the device by the handles <NUM>, <NUM> and linkages <NUM>, <NUM>, the main spring <NUM> is compressed. <FIG> shows the main spring <NUM> in a partially compressed state, <FIG> shows the main spring <NUM> in a fully compressed state. It is important to note that the particular configuration of handles, linkages, a return sleeve and main spring illustrated in the figures is not limiting. Other mechanical configurations could be used to implement the functionality of handle closure acting to compress the main spring and charging an alternative embodiment of needle-free injection device.

Returning to <FIG>, it may be noted that the latch and release sleeve <NUM> includes an upper latching member <NUM> and a lower latching member <NUM>. Each handle <NUM>, <NUM> has a corresponding latching surface with the upper handle <NUM> having an upper latching surface <NUM> and the lower handle <NUM> having a lower latching surface <NUM>. In use, the upper latching member <NUM> engages the upper latching surface <NUM> when the handles <NUM>, <NUM> are in a fully closed position. The lower latching member <NUM> and lower latching surface <NUM> engage in the same way. Thus, when the handles <NUM>, <NUM> are closed to the fully closed configuration illustrated in <FIG>, the handles <NUM>, <NUM> are latched shut. The handles <NUM>, <NUM> when placed in the <FIG> closed position are configured to remain latched shut until such time as the release button <NUM> is depressed, moving the latch and release sleeve <NUM> forward a short distance with respect to the injector tube <NUM> which causes the latch members <NUM>, <NUM> and latch surfaces <NUM>, <NUM> to disengage returning the needle-free injection device <NUM> to the <FIG> configuration. As will be described below, the release button <NUM> cannot operate to release the main spring <NUM> under any circumstance providing used safety.

It may also be noted by comparison of <FIG>, <FIG> that as the return sleeve <NUM> is moved away from the syringe end <NUM> of the needle-free injection device <NUM>, one or more return springs <NUM> are extended. Return spring extension biases the return sleeve <NUM> toward the syringe end <NUM> of the needle-free injection device <NUM> such that the return sleeve <NUM> is motivated to slide forward when the handles <NUM>, <NUM> are opened.

<FIG> and <FIG> are side elevation and perspective cross-sectional views of the needle-free injection device <NUM> in the handle open/ready to charge position of <FIG>. <FIG> and <FIG> are perspective and front elevation cross sectional views of needle-free injection device <NUM> after the main spring has been compressed (<FIG>) and after a skin tensioning spring has also been compressed, as described in detail below (<FIG>). In the <FIG> views, the handles <NUM>, <NUM> and various other structures have been removed to provide a more detailed view of the return sleeve <NUM>, main spring <NUM>, hammer <NUM> and associated apparatus. In particular, <FIG> shows the engagement of the upper linkage <NUM> and lower linkage <NUM> with corresponding surfaces on the return sleeve <NUM> such that closing the handles <NUM>, <NUM> causes the linkages <NUM>, <NUM> to force the return sleeve <NUM> and hammer away from the syringe end <NUM> of the needle-free injection device <NUM> thereby compressing the main spring <NUM>.

As also shown in the <FIG> view, side posts <NUM> extend from the portion of the hammer <NUM> adjacent the main spring <NUM>. The side posts could be independent structures, or as shown in <FIG> a pin extending through the hammer. The side posts <NUM> are engaged with clips <NUM> when the return sleeve is retracted. Thus, the clips <NUM> bind the hammer <NUM> to the return sleeve <NUM> when the needle-free injection device <NUM> is in an open and ready to charge configuration and as the device is charged. As best shown in <FIG>, as the needle-free injection device <NUM> nears and reaches the fully charged position, ball bearings <NUM> associated with a ball lock sleeve <NUM> drop into a notch <NUM> defined in the hammer. Thus, the ball lock sleeve <NUM> and associated apparatus lock the hammer <NUM> in a charged position at a time when the clips <NUM> are still engaged with the side posts <NUM>. When the handles <NUM>, <NUM> are fully closed, the clips <NUM> move into engagement with the ramped front surface <NUM> of the return sleeve to be forced away from the side posts <NUM> and therefore to allow for subsequent clearance between the side posts and the return sleeve as the device is fired.

As is best shown in <FIG>, <FIG> and <FIG>, when the needle-free injection device <NUM> is placed in a fully charged configuration and the handles <NUM>, <NUM> are locked; a needle-free syringe <NUM> may be placed into the syringe receptacle <NUM>. As described in detail below, the needle-free injection device <NUM> includes various safety systems to assure that an inadvertent injection is not made when the needle-free syringe <NUM> is placed into the syringe receptacle <NUM> or at any other time.

In particular, it may be noted by comparing <FIG> with <FIG> that the combined elements of the syringe receptacle <NUM>, a needle-free syringe <NUM>, the hammer <NUM>, main spring <NUM> and ball lock sleeve <NUM> may all be moved, in association with the injector tube <NUM> housing the main spring and hammer, laterally away from the syringe end of the pivot sleeve <NUM> and associated handles. A skin tensioning spring <NUM> is provided which biases against the lateral rearward movement of the injector tube <NUM>. See for example <FIG> where the skin tensioning spring <NUM> is not compressed and <FIG> where the skin tensioning spring <NUM> has been compressed. The rearward movement of the injector syringe receptacle <NUM>, needle-free syringe <NUM>, hammer <NUM>, main spring <NUM> and ball lock sleeve <NUM> is important for two distinct reasons. First, prior to an injection, the nozzle end <NUM> of a needle-free syringe <NUM> is placed against a patient's skin and the needle-free injection device <NUM> is pressed toward the patient with sufficient force to compress the skin tensioning spring <NUM>. This action, in conjunction with the specific shape of the nozzle end <NUM>, causes the patient's skin to be appropriately tensioned to assure that a suitable injection is made. It may be noted from a comparison of <FIG> and <FIG> or <FIG> with <FIG> that both the forward end <NUM> of the syringe receptacle <NUM> and the rear end <NUM> of the injector tube <NUM> slide backward (away from the syringe end <NUM> of the device) with respect to other elements of the needle-free injection device <NUM> as the skin tensioning spring is compressed. This functionality provides for proper skin tensioning as described above and also is linked to device safety as described below.

The needle-free injection device <NUM> is provided with an actuation button <NUM> which in certain instances releases the main spring to provide an injection. As shown in <FIG> and <FIG>, when the needle-free injection device <NUM> is fully armed, the skin tensioning spring <NUM> is fully compressed and the injector tube and the elements within or attached to the injector tube are moved or slid fully away from the syringe end of the device as described above, the actuation button <NUM> communicates with the ball lock sleeve <NUM> through activation linkage <NUM>. As shown in <FIG>, when the actuation button <NUM> is depressed in this fully charged and armed configuration, the activation linkage <NUM> forces the ball lock sleeve <NUM> toward the rear of the device a short distance freeing the ball bearings <NUM> from the notch <NUM> allowing the main spring <NUM> to rapidly decompress, forcing the hammer <NUM> into contact with the plunger <NUM> of the needle-free syringe <NUM>. As shown in <FIG> and <FIG>, however, the activation linkage <NUM> is not positioned in physical communication with the actuation button <NUM> until such time as the injector tube <NUM> and associated apparatus have been moved fully toward the rear of the needle-free injection device <NUM> by skin tensioning pressure on the nozzle end <NUM> of the needle-free syringe <NUM>. Thus, the needle-free injection device <NUM> cannot be activated and an injection cannot be delivered in normal use unless the nozzle end <NUM> of the needle-free syringe <NUM> is placed against a patient's skin and the needle-free injection device <NUM> is pressed forward with sufficient force to compress the skin tensioning spring <NUM> and thereby properly tension the skin.

Additional safety is provided by the retract button <NUM> and associated apparatus. As is most readily seen in <FIG>, the retract button <NUM> communicates with a safety collar <NUM> having a notch <NUM> defined therein. The notch <NUM> corresponds with a tab <NUM> extending from an exterior surface of the syringe receptacle <NUM>. As noted above, the syringe receptacle <NUM>, injector tube <NUM>, hammer <NUM> and syringe <NUM> may all be made to collectively slide or otherwise move toward the rear of the needle-free injection device <NUM> when appropriate skin tension is applied to the nozzle end <NUM> of the syringe <NUM>. The tab <NUM> interferes with the safety collar <NUM> preventing rearward motion of the above assemblies until such time as the retract button <NUM> is depressed. Thus, in normal use, even though the main spring may be compressed, the device cannot be placed into a firing or injection-enabled configuration without first depressing the retract button <NUM>. As noted above, the actuation button <NUM> cannot be engaged with the ball lock sleeve <NUM> until the injector tube <NUM> has been moved into a firing or injection configuration. Accordingly, a very high degree of safety is provided by the cooperation of the retract button <NUM> and actuation button <NUM> and associated assemblies. The device can not be accidentally placed into a firing position because of the retract button and the device can not be fired until it is intentionally placed into a firing position.

In certain embodiments the handles <NUM>, <NUM> are fabricated from a plastic or other injection molded material. The handles <NUM>, <NUM> experience substantial force when closed to compress the main spring <NUM> and charge the needle-free injection device <NUM>. Accordingly, effective needle-free injection device <NUM> operation and longevity may be enhanced by providing a hinge which more fully supports handle pivot operation when compared to traditional pivot pins. <FIG> is a detailed perspective view of a pivot plate <NUM>, one of which is located on each side of the device to support and provide for suitable pivoting of the upper and lower handles. Each pivot plate <NUM> includes an upper pivot stud <NUM> and lower pivot stud <NUM> which receive and support corresponding holes in the upper and lower handles <NUM>, <NUM> providing for pivoted handle articulation. The pivot plates <NUM> also include upper and lower radius surfaces <NUM>, <NUM>, respectively. The upper and lower radius surfaces <NUM>, <NUM> are configured to mate with a corresponding surface on the inside of each handle <NUM>, <NUM> to provide support to the handle as it is move from an open to a closed position. Together, the pivot studs <NUM>, <NUM> and upper and lower radius surfaces <NUM>, <NUM> provide each handle <NUM>, <NUM> with significantly enhanced support when compared to a simple pivot pin type attachments.

<FIG> include several views of a needle-free syringe <NUM> and syringe plunger system <NUM> showing certain enhancements. In particular, the needle-free syringe <NUM> may include at least two raised surfaces <NUM> defining at least one orientation channel <NUM> on the body of the needle-free syringe, typically at the trailing end. The orientation channel <NUM> is sized and configured to engage with corresponding syringe orientation guides associated with the syringe receptacle <NUM>. Thus, a user may install a needle-free syringe <NUM> by sliding one or more orientation channels <NUM> over corresponding orientation guides until the pawls or another engagement mechanism engage with the syringe. Therefore, a syringe may be installed and locked for use without requiring the syringe body to be twisted as is necessary with conventional bayonet or screw type syringe mounts. The needle-free syringe <NUM> may also include visual indicia <NUM> which are illustrated as small raised portions but which could be implemented with any visually observable marker. In use, the visual indicia are placed in a visually identifiable position relative to or concealed by the forward end <NUM> of the syringe receptacle <NUM> thereby providing visual confirmation that a syringe <NUM> is properly installed.

It may be convenient to remotely prepare multiple needle-free syringes <NUM> for use with the needle-free injection device <NUM>. For example, one operator could be loading needle-free syringes with an injectable fluid while another operator installs the needle-free syringes into the device and performs injections. Remote filling to a proper pre-determined dosage is facilitated by providing a plunger system <NUM> which includes a plunger body <NUM> and a seal sized to fit in fluid-tight engagement with the interior chamber of the syringe, thereby defining a fluid receiving dosage space within the needle-free syringe <NUM>. As shown in <FIG>, the plunger system <NUM> also may include a handle <NUM>. The handle <NUM> may be conveniently separated from the plunger body <NUM> at a break line <NUM> defined in a separable shaft between the plunger body and handle. In use the handle <NUM> and separable shaft are typically broken away from the plunger body at the break line <NUM> after the syringe is filled, but before it is loaded into a device <NUM>. Upon removal of the handle <NUM> and separable shaft, the trailing end of the plunger body <NUM> defines a hammer surface <NUM> which engages with the hammer <NUM> during an injection.

As shown in <FIG>, the interior portion of the syringe <NUM> defines a dosage space <NUM> within the interior walls of the syringe between the nozzle and the plunger seal. This dosage space may be sized and configured to have a pre-selected injectable fluid dosage volume when the plunger body <NUM> is positioned within the syringe such that the hammer surface <NUM> is placed in a pre-defined spatial relationship with a dose setting surface <NUM> on the trailing edge of the syringe, substantially opposite the nozzle <NUM> (see <FIG>). For example, the dosage space <NUM> may be sized to have a specific volume, for example <NUM>, when the hammer surface <NUM> is coplanar with the dose setting surface <NUM>.

As shown in <FIG>, the hammer <NUM> may be used to automatically position the plunger body <NUM> such that the hammer surface <NUM> and dose setting surface <NUM> are coplanar. For example, the syringe and plunger assembly may be loaded into the needle-free injection device <NUM> with the hammer surface <NUM> extending slightly beyond the dose setting surface <NUM> and the location of the corresponding end of the hammer <NUM> causes these two surfaces to become coplanar. It may also be noted that the leading edge of the hammer <NUM> may include a recess which provides clearance for any extension or nub remaining beyond the hammer surface <NUM> when the separable shaft is removed from the plunger body <NUM> at the break line <NUM>.

Proper dose setting may also be accomplished in the absence of the needle-free injection device <NUM> by using the plunger positioning surface <NUM> associated with the handle <NUM> to manually position the hammer surface <NUM> to be coplanar with the dose setting surface <NUM>. The plunger positioning surface <NUM> may, as shown in <FIG>, include a hole <NUM> which provides clearance for any extension or nub formed in the hammer surface <NUM> upon separation of the plunger body from the handle at the break line. Thus, during a remote filling operation, a user may insert the plunger body <NUM> and attached handle assembly <NUM> fully into a needle-free syringe <NUM> such that the leading end of the plunger body <NUM> is in contact with the interior surface of the nozzle. The nozzle may be placed in fluid communication with a supply of injectable material. The handle may be then be used to withdraw the plunger body <NUM> to a point where the hammer surface <NUM> extends beyond the dose setting surface <NUM> of the syringe, thereby slightly over-filling the syringe. The handle and separable shaft may then be removed at the break line <NUM> and the hammer surface and dose setting surface <NUM> made to be coplanar (thus precisely setting the selected dosage) by pressing upon the hammer surface with the plunger positioning surface <NUM> of the handle. The foregoing operation may be performed while the nozzle is continuously maintained in sterile fluid communication with an injectable substance supply, thus minimizing waste.

Returning to <FIG> it may be noted that the needle-free syringe <NUM> may be provided with a cap <NUM> sized to engage the nozzle end of the syringe body. <FIG> include several alternative views of a needle-free syringe <NUM> as described herein.

Alternative embodiments include methods of charging, operating and filling a needle-free injector as described above. For example, one embodiment includes a method of arming a needle-free injection device comprising the steps of providing a needle-free injection device or system as disclosed above, moving one or more handles associated with the needle-free injection device from an open position to a closed position thereby compressing the main spring of the needle-free injection device from an un-armed to an armed position.

As more particularly shown in the flow chart of <FIG>, a method <NUM> may include the steps of moving at least one handle from an open to a closed position to compress the main spring of injection device (Step <NUM>). Next, a needle-free syringe may be loaded into the injection device (Step <NUM>). A user may then activate a retract button to unlock an injector tube within the device, allowing the device to be positioned for an injection (Step <NUM>). As noted above, the injector cannot be fired at this point in time because the firing or injection enabling mechanism is not in mechanical communication with actuation button. Immediately prior to injection, the user may apply force against a subject's skin at the nozzle end of the needle-free syringe, causing the injector tube to move laterally into an injection firing position. (Step <NUM>). As noted above movement into the firing/injection position may be prohibited unless the retract button has been depressed. Then, with the patient's skin properly tensioned, the user may activate an actuation button to release the energy stored in the main spring to drive the syringe plunger causing an injection (Step <NUM>).

Claim 1:
A needle-free injection device (<NUM>) having a syringe end (<NUM>), the needle-free injection device comprising:
an injector tube (<NUM>);
a compressible main spring (<NUM>) which can be selectively compressed to place the needle-free injection device (<NUM>) in an armed configuration, the main spring being positioned within the injector tube (<NUM>);
a hammer (<NUM>), the hammer being positioned within the injector tube (<NUM>);
an upper handle (<NUM>) pivotally attached to the needle-free injection device (<NUM>) such that the upper handle (<NUM>) pivots between an open and a closed position;
a return sleeve (<NUM>) engaged with the main spring (<NUM>); and
an upper linkage (<NUM>) engaged with the upper handle (<NUM>) and the return sleeve (<NUM>), wherein the upper linkage (<NUM>) causes the return sleeve (<NUM>) to move away from the syringe end, causing the main spring (<NUM>) to be compressed into the armed configuration, when the upper handle (<NUM>) is moved from the open to the closed position,
characterized in that
the return sleeve (<NUM>) is positioned outside of the injector tube (<NUM>), and
the needle-free injection device further comprises a return spring (<NUM>) biasing the return sleeve (<NUM>) toward the syringe end of the needle-free injection device (<NUM>).