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.

Thus, a great deal of attention has been given to the development of needle-free injection devices and methods which are safe, reliable and easy to use in the field. Needle-free technologies raise certain unique engineering challenges which are likely to be encountered when designing a suitable device. For example, conventional needled syringes are often inexpensive or disposable devices. Thus a large supply of pre-filled syringes can be prepared for large scale inoculation projects. On the other hand, needle-free devices are typically more expensive since these devices require a relatively sophisticated pneumatic, electronic or spring power source, energizing system and triggering system. Although a needle-free device can be designed to accept disposable (or recyclable) needle-free syringes, it can be difficult to quickly and accurately load a pre-filled needle-free syringe into an injection device, particularly without contaminating the injection nozzle. Similarly, it can be difficult to remove a spent needle-free syringe and replace same with an unused syringe quickly, efficiently and in a sterile manner. Thus, known needle-free injection devices can be difficult to use for large scale inoculation projects or in other situations where a significant number of injections are made to a relatively large group of patients.

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 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. 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.

<CIT> discloses multi-component ampules for use with reusable and disposable jet injectors. The ampules define a medicine space that is suitable for storing medications and the like for prolonged period.

A first aspect of the present invention comprises a needle-free syringe system as set out in claim <NUM>.

A second aspect of the present invention comprises a plunger system for a needle-free syringe system as set out in claim <NUM>.

A third aspect of the present invention comprises a method of filling a needle-free syringe system as set out in claim <NUM>.

Described herein is a needle-free injection device having an outer housing and an inner housing. The inner housing is configured to receive a needle-free syringe in one end. In addition, the inner housing is movable within the outer housing between a syringe loading position and a firing position. This arrangement also includes an activation button operatively associated with the inner and outer housings and a housing lock engaged by the activation button to prohibit movement of the inner housing from the syringe loading position to the firing position when the activation button is activated with the inner housing in the syringe loading position.

Generally, a syringe loading position is defined for any device as a configuration between inner and outer housings where syringe loading or syringe ejection is enabled and injection operations are substantially prohibited. In addition, for any device, a firing position is defined as a configuration between inner and outer housings where injection is enabled.

The housing lock of the above arrangement may be implemented with any suitable mechanism which serves to lock the inner housing in the syringe loading position with respect to the outer housing. For example, the housing lock can include an engagement surface on the activation button that mates with a corresponding recess on the inner housing.

In certain arrangements, the needle-free injection device further includes a powered hammer within the inner housing communicating with a plunger within a needle-free syringe. The hammer is released with a release mechanism to provide stored energy to the plunger to power an injection. Furthermore, the activation button is configured to only engage the release mechanism when the housing is in the firing position. Thus, in this arrangement, the activation button has at least two distinct functions. The activation button operates to lock the needle-free injection device in the syringe loading position when it is depressed or otherwise activated while in the syringe loading position and the same activation button operates to trigger the device and release stored energy to power the hammer, thus causing an injection, if the activation button is activated with the inner housing in the syringe loading position.

The release mechanism may be implemented with any suitable mechanism. For example, the release mechanism can comprise a lever associated with the activation button and a ball lock sleeve associated with the lever and the hammer such that articulation of the lever moves the ball lock sleeve thereby releasing the hammer. The hammer may be powered by any suitable pneumatic, spring, electronic or other power source.

In some arrangements, the needle-free injection device further includes a syringe mount to receive a needle-free syringe at one end of the inner housing. The syringe mount comprises an interlocking structure cooperating with the inner housing and outer housing to prevent the placement of a needle-free syringe into engagement with the syringe mount unless the inner housing is in the syringe loading position. The syringe mount and associated interlocking structure may be implemented with any suitable components, for example, the syringe mount and interlocking structure can comprise at least one rotating pawl providing for engagement with the needle-free syringe. A tab is provided toward the exterior of at least one pawl and a corresponding opening is provided through the inner housing. In addition, a corresponding space is provided within the outer housing such that the pawl can rotate to receive a syringe only if the opening through the inner housing is aligned with the space within the outer housing, for example, when the inner housing is in the syringe loading position. Alternatively, the pawl may be prohibited from rotating if the inner housing is not in a syringe loading position by tab interference with a corresponding portion of the outer housing.

The interlocking structure can also be configured to engage with the inner housing after a needle-free syringe is loaded such that force applied to a nozzle end of the needle-free syringe causes the inner housing to move from the syringe loading position toward the firing position. In addition, the interlocking structure can cooperate with the inner housing and outer housing to substantially prevent the removal of a needle-free syringe from engagement with the syringe mount unless the inner housing is in the syringe loading position. Furthermore, the interlocking structure can cooperate with the inner housing and outer housing to prevent the inner housing from being moved from the syringe loading position to the firing position if a syringe has been improperly loaded in the syringe mount.

Arrangements of the needle-free injection system further comprise an eject button associated with the syringe mount such that activation of the eject button causes the syringe mount to release a previously mounted needle-free syringe. Inadvertent syringe ejections are substantially prevented by providing an extension on the outer housing that at least partially shields the eject button when the inner housing is moved from the syringe loading position toward the firing position. In addition, the interlocking structure can prevent ejection unless the inner housing is in the syringe loading position. The system may optionally be provided with a syringe eject spring which provides sufficient force to completely eject a needle-free syringe away from any contact with the needle-free injection system upon activation of the eject button.

The needle free injection system may also comprise a needle-free syringe. The needle-free syringe may include at least two raised surfaces on the syringe body defining at least one orientation channel configured to mate with an orientation structure of the syringe mount. The syringe may further include a grip edge defined at least in part by the raised surfaces which engages the syringe mount when a needle-free syringe is mounted. The foregoing structures may be implemented to allow the mounting of a needle-free syringe without requiring rotation the syringe body or syringe mount to lock the syringe to the syringe mount. Furthermore, the foregoing structures and associated syringe mount and ejection structures may provide for the mounting, use and subsequent ejection of a needle-free syringe from the system without requiring that the syringe be touched or grasped by an operator's hand at any step of the process.

The foregoing arrangements of needle-free injection systems are described as including a multi-purpose activation button, housing lock and release mechanism subsystem, a syringe mount and interlocking structure subsystem and various features associated with a suitable needle-free syringe itself. Alternative device arrangements may include any combination of one or more of the foregoing subsystems or structures.

An embodiment according to the present invention includes a needle-free syringe comprising a syringe body having a nozzle at one end and a dose setting surface substantially opposite the nozzle. The needle-free syringe further includes a plunger body having a leading end, a seal and a hammer surface substantially opposite the leading end. In this configuration, the syringe body defines a dosage space within the syringe between the nozzle, interior syringe walls and the plunger seal. The dosage space has a select dosage volume when the plunger body is positioned within the syringe body such that the dose setting surface and hammer surface are coplanar. The selected dosage volume may be any suitable amount, for example, <NUM>.

The needle-free syringe system further includes 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 arrangement, 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.

The needle-free syringe system may further include a filling adapter. The filling adapter mates with the syringe body for filling operations. A fluid tight seal between the adapter and syringe body may be made by providing either the filling adapter or the syringe body with a female conical surface and providing the other of the syringe body or filling adapter with a corresponding male conical surface. The corresponding male and female conical surfaces form a fluid tight seal upon the attachment of the filling adapter to the nozzle end of the syringe body without the requirement of a separate compliant sealing member such as an o-ring.

The needle-free syringe system may also include a cap having an open ended cap body size to engage and protect the nozzle end of the syringe body and an annular flange at a closed end of the cap body which provides a stand surface having a diameter greater than the diameter of the open end of the cap body.

Another embodiment of the present invention is a plunger and handle system for any needle-free syringe as described above. Also described herein is a filling adapter for any needle-free syringe system as described above.

Also described herein is a method of operating a needle-free injector. The method includes providing a needle-free injection device according to one of the arrangements described above. The method further includes activating the activation button to lock the inner housing in the syringe loading position and subsequently loading a needle-free syringe into the injector. An operator may then release the activation button and move the inner housing to the firing position by pressing the nozzle end of the needle-free syringe against the injection site with sufficient force. The injection may then be triggered by activating the activation button when the inner housing is fully in the firing position. Optionally, the method may include steps of loading and ejecting a needle free syringe from the device. Loading and ejection may occur without touching the syringe at any time.

Another embodiment is a method of filling a needle-free syringe including providing a syringe body having a nozzle at one end and a dose setting surface substantially opposite the nozzle and providing a plunger body in sealed engagement with an inner surface of the syringe body where the plunger body further comprises a hammer surface. The filling method further comprises positioning the hammer surface to be substantially coplanar with the dose setting surface.

Another method of filling a needle-free syringe may include providing a filling adapter with a filling needle in sealed fluid communication with the nozzle of the syringe body. The plunger system including a handle as described above may be placed into engagement with the syringe. The plunger body may then be moved forward to the nozzle end of the syringe body. The septum of storage vial of injectable fluid may be pierced with the filling needle. The plunger system is then withdrawn by the handle to a position where the break line is beyond the dose setting surface. The handle is then removed from the plunger body by separating the shaft at the break line. Next, the plunger body may be moved toward the nozzle by applying force against the hammer surface with a plunger positioning surface causing the hammer surface and dose setting surface to become coplanar. Alternatively, the dose may be set by using a surface within the device, for example the leading edge of the hammer, to cause the hammer surface to become coplanar with the dose setting surface. Throughout the dose setting operation the filling adapter and needle-free syringe remain in direct fluid communication with the storage vial of injectable fluid, thereby allowing the precise setting of an injection dosage without the waste of any substantial amount of injectable fluid.

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 representative needle-free injection device <NUM> is further illustrated in the front elevation cross-section views of <FIG> and <FIG>. The views of <FIG> and <FIG> show the needle-free injection device <NUM> in various operational states as described in detail below. The needle-free injection device <NUM> includes an outer housing <NUM> and an inner housing <NUM>. Although the outer housing <NUM> and inner housing <NUM> are shown separated into two halves in <FIG>, this is a non-limiting fabrication choice. The housings may be fabricated from any suitable material in any number of sub-components provided the housings operate with respect to each other as described herein. In the arrangement illustrated in <FIG>, the outer housing <NUM> defines the exterior of a substantially cylindrical needle-free injection device which is conveniently sized for hand-held use. Both the device <NUM>, outer housing <NUM> and inner housing <NUM> are described herein as having a leading end <NUM> which is defined as the injection end of the device generally associated with a needle-free syringe (see for example <FIG>). In addition, the device housings and syringe are described herein as having a trailing end <NUM> substantially opposite the leading end <NUM>.

The foregoing position and shape descriptions are provided for convenience only and do not create any limiting configuration. For example, the needle-free injection device <NUM> is illustrated herein as being substantially cylindrical and sized for convenient hand-held use. The various features, elements, components and methods described herein are however applicable to other shapes, sizes and configurations of device. Thus, terms such as leading end and trailing end are provided merely to aid in the description of the representative arrangement and are not intended to limit the scope of any claimed embodiment.

As shown in <FIG>, the inner housing <NUM> is movable within the outer housing <NUM> between a syringe loading position and a firing position. In particular, <FIG> shows the device <NUM> in a storage configuration prior to or after use. <FIG> shows the device <NUM> with a needle free syringe <NUM> installed. Both <FIG> and <FIG> illustrate a needle-free injection device <NUM> with the inner housing <NUM> positioned in what is defined herein as the syringe loading position. In <FIG> and <FIG> it may be noted that the inner housing <NUM> is positioned toward the leading end <NUM> of the device with respect to the outer housing <NUM>. This configuration is specifically the syringe loading position of this particular arrangement. More generally, a syringe loading position is defined for any device as a configuration between inner and outer housings where syringe loading or syringe ejection is enabled and injection is substantially prohibited.

In addition, for any configuration of device, a firing position is defined as a configuration between inner and outer housings where injection is enabled. As discussed in detail below the safety and efficiency of a device may be enhanced by providing distinct syringe loading and firing configurations. <FIG> illustrates the needle-free injection device <NUM> in the firing position, for this arrangement. In particular, <FIG> shows the inner housing <NUM> positioned within the outer housing <NUM> toward the trailing end of the device. As described in detail below the movement of the inner housing from a syringe loading position to a firing position provides numerous safety and injection reliability advantages. It should be noted that the specific configurations of <FIG> are not limiting. As described above, other configurations or relationships between an inner housing movable with respect to an outer housing could define different syringe loading positions or firing positions for an alternative device configuration.

The needle-free injection device <NUM> also includes an activation button <NUM> operatively associated with both the outer housing <NUM> and inner housing <NUM>. As described in detail below, the activation button <NUM> may be configured to activate various device functions depending upon the positional relationship between the inner housing <NUM>, outer housing <NUM> and other elements of the needle free injection device <NUM>.

It may be desired in selected arrangements to provide a housing lock <NUM> which prohibits movement of the inner housing <NUM> with respect to the outer housing <NUM>. For example, a housing lock <NUM> may provide safety by prohibiting movement of the inner housing <NUM> from the syringe loading position to the firing position during a syringe loading procedure. In the arrangement of <FIG>, the housing lock <NUM> may be engaged by depressing the activation button <NUM> while the device is in the syringe loading position. In particular, as shown in <FIG>, the activation button <NUM> may include an engagement surface <NUM> which, when the button <NUM> is depressed, mates with a corresponding recess <NUM> to prohibit movement of the inner housing <NUM> toward the trailing end of the device, thus locking the device in the syringe loading position. The inclusion of a housing lock <NUM> minimizes the risk of inadvertently firing the needle-free injection device <NUM> during preliminary procedures such as syringe loading.

The needle-free injection device <NUM> illustrated in <FIG> also includes a hammer <NUM> configured to drive a syringe plunger <NUM> forward providing for an injection. In the arrangement of <FIG> and <FIG> the hammer <NUM> is energetically driven toward the plunger <NUM> by energy previously stored compressing a main spring <NUM>. Main spring <NUM> is shown in an un-compressed state in <FIG> and compressed in <FIG>. It is important to note that the arrangements disclosed herein are not limited to needle-free injection devices <NUM> which rely upon a spring for injection power. The elements, components and methods described herein could be implemented in a pneumatic device, an electronically driven device or any other type of needle-free injector. Thus, in alternative some arrangements the main spring <NUM> could be replaced with a compressed gas source, pneumatic chamber, a motor, an electromagnet or other power source.

The device of <FIG> further includes a release mechanism <NUM> operatively associated with the hammer <NUM> such that the release mechanism <NUM> can be activated to initiate the release of energy stored in the main spring <NUM> to power the hammer <NUM> and thereby cause an injection. In the particular arrangement illustrated in <FIG> the release mechanism <NUM> includes a lever <NUM> and ball lock sleeve <NUM> which cooperate to releases the hammer <NUM> when the lever is articulated by the activation button <NUM>. Comparison of <FIG> with <FIG> shows that the lever <NUM> is intentionally not in mechanical communication with the activation button <NUM> until such time as the inner housing <NUM> is moved from the syringe loading position to the firing position. Thus, the activation button <NUM> cannot fire the device unless the device is in the firing position. Therefore, the single activation button <NUM> may be depressed to lock the inner housing during loading procedures in the syringe loading position or alternatively depressed to fire the device when the inner housing has been moved to the firing position. The configuration of the housing lock <NUM> and release mechanism <NUM> guarantee that the activation button <NUM> can only perform the appropriate function at the appropriate time based upon the positioning of the inner housing.

The specific arrangement illustrated in <FIG> accomplishes firing by the articulation of the lever <NUM> with the activation button <NUM> while the inner housing is in the firing position as shown in <FIG>. The lever <NUM> rotates around a pivot <NUM> and pushes the ball lock mechanism <NUM> toward the trailing edge of the device. When the ball lock mechanism <NUM> is moved back a suitable distance, ball bearings <NUM> are released from a notch <NUM> in the hammer <NUM> and forced into channels <NUM> of the ball lock, thus releasing the hammer <NUM> to power an injection. It is important to note that any alternative triggering mechanism which is suitable for articulation by the activation button <NUM> may be used to implement or cause the firing of the device.

The ability of the functional elements of the needle-free injection device <NUM> to enhance the safety and reliability of an injection in both the syringe loading position and firing position are described in additional detail below. Initially, it may be noted that the device <NUM> includes a skin tensioning spring <NUM> positioned between the outside trailing end of the inner housing <NUM> and the inside trailing end of the outer housing <NUM>. The skin tensioning spring <NUM> element may be implemented with a compression spring which has a relatively lower spring constant than the main spring <NUM>. Alternatively, other compression elements such as elastomeric rings or wave washers could be used to implement the skin tensioning spring <NUM>. The skin tensioning spring <NUM> installed as shown in <FIG> will bias the inner housing <NUM> toward the syringe loading position.

As described above, the activation button <NUM> may be used to engage a housing lock <NUM> locking the inner housing <NUM> into the syringe loading position for syringe loading or other pre-injection tasks. Prior to an injection the housing lock <NUM> may be released and the nozzle end <NUM> of a needle-free syringe <NUM> placed against a patient's skin at the injection site. It is important for both safety and injection consistency that the patient's skin be placed under appropriate tension prior to the needle-free injection. Appropriate skin tension is accomplished in the needle-free injection device <NUM> as force against the skin by the nozzle end <NUM> is transferred through the syringe <NUM> to the inner housing thereby causing the inner housing to move toward the firing position and compressing the skin tensioning spring <NUM>. Thus, as shown by comparing <FIG> and <FIG>, compression of the skin tensioning spring <NUM> occurs in conjunction with movement of the inner housing <NUM> toward the firing position. Furthermore, compression of the skin tensioning spring <NUM> requires the operator to press the nozzle end <NUM> of the syringe against the patient's skin with an appropriate force. The operator is holding the outer housing <NUM> during an injection so the physical act of pressing the nozzle end <NUM> against the patient's skin with sufficient force causes the configuration of the inner housing <NUM> with respect to the outer housing <NUM> to move from the syringe loading position to the firing position. Since the skin tensioning spring resists this movement, appropriate injection site skin tension is tunable for different situations by selecting an appropriately sized skin tensioning spring <NUM> or providing an adjustable spring pre-load.

As shown in <FIG> the needle free injection device <NUM> will typically be delivered to an end user without a needle-free syringe <NUM> attached. As described in detail below, a user may fill multiple needle-free syringes <NUM> with an injectable fluid in advance, possibly at a remote location away from the needle-free injection device <NUM>. Advance preparation of multiple needle free syringes <NUM> facilitates large inoculation projects for example.

Thus, the needle-free injection device <NUM> is configured to efficiently and accurately receive, hold and eject a needle-free syringe <NUM>. The installed needle-free syringe <NUM> may be selected from a supply of prefilled syringes. In addition it may optionally be desirable that a syringe can be mounted and ejected without touching the syringe body with an operator's hands to minimize the risk of syringe contamination or operator injury. Accordingly, the needle-free injection device <NUM> may include a syringe mount <NUM>, an interlocking structure <NUM>, and an ejection mechanism <NUM> which separately or together enhance several aspects of the safe use of the device.

For example, as shown in the top cross sectional views of <FIG> the needle-free injection device <NUM> may include a syringe mount <NUM> comprising a socket <NUM> sized to receive a suitable needle-free syringe <NUM>. Pawls <NUM> or a similar grasping or locking structure may be provided adjacent to the socket and configured to positively grip an appropriate grip surface <NUM> on a needle-free syringe <NUM>. It may be noted from <FIG> which shows a needle-free injection device <NUM> in the syringe loading position while a syringe is in the process of being loaded that the trailing end of the syringe <NUM> is received in an ejection sleeve <NUM> and an ejection spring <NUM> is compressed. The ejection sleeve <NUM> and ejection spring <NUM> facilitate the optional hands free ejection of a syringe as described below.

The safe and efficient use of the needle-free injection device <NUM> may be further enhanced if the device is provided with an interlocking structure <NUM> which prevents the placement of a needle-free syringe <NUM> into an engagement with the syringe mount <NUM> unless the inner housing <NUM> is in the syringe loading position. Alternatively, or in addition to this functionality, the interlocking structure <NUM> may prevent removal of a needle-free syringe <NUM> unless the inner housing <NUM> is also in the syringe loading position. One representative and non-limiting example of an interlocking structure <NUM> may be viewed in <FIG> and includes at least one tab <NUM> on an outer perimeter surface of a pawl <NUM>. The tab <NUM> corresponds with an opening <NUM> defined by the inner housing <NUM> and a corresponding open area <NUM> within the outer housing <NUM> such that the tab <NUM> may extend through the opening <NUM> into the area <NUM> when the pawls <NUM> rotate outward and extend over the trailing end of a suitably shaped needle-free syringe <NUM>. <FIG> in particular shows the tab <NUM> extending through the opening <NUM> and into the area <NUM> as a needle-free syringe <NUM> is in the process of being mounted.

In addition, as shown in <FIG> the tab <NUM> may extend through the opening <NUM> into the area <NUM> when the pawls <NUM> rotate outward as an inner release mechanism <NUM> is articulated by an eject button <NUM>. Several safety and efficiency attributes are provided by the interlocking structure <NUM> because the tab <NUM> will only correspond with the open area <NUM> within the outer housing <NUM> when the inner housing <NUM> is in the syringe loading position. Any possibility that the tab <NUM> might extend beyond the inner housing when the inner housing is positioned away from the syringe loading position is prohibited by providing the outer housing <NUM> with one or more abutment surfaces <NUM> which prevent a tab <NUM> from extending beyond the outer surface of the inner housing <NUM> if the inner housing <NUM> has moved to or toward the firing position. See for example <FIG> which is a top plan cross section view of the device in the firing position. Thus, the interface between tab <NUM> and abutment surface <NUM> prevents inadvertent ejection of a syringe in either the firing position or in an intermediate position between the syringe loading position and the firing position.

Furthermore, an improperly loaded syringe will prevent the pawls <NUM> from rotating into secure contact with the grip surface <NUM> of a needle-free syringe <NUM>. Thus, an improperly loaded syringe will cause tab <NUM> to extend into the open area <NUM> within the outer housing <NUM>. Accordingly, a device with an improperly loaded syringe cannot have the inner housing moved into the firing position because tab <NUM> will interfere with abutment surface <NUM>, preventing movement of the inner housing toward the trailing end of the device.

Referring back to <FIG> which shows a loaded needle-free injection device <NUM> in the firing position, it may be noted that supplemental safety may be provided by including an extension <NUM> on the outer housing that fully or partially shields the eject button <NUM> when the inner housing <NUM> is moved from the syringe loading position toward the firing position.

The syringe ejection spring <NUM> may be selected to provide enough force to completely eject a spent needle-free syringe <NUM> from the device <NUM> without requiring a user to touch the needle-free syringe. Alternatively, a device can be configured to only partially release a syringe which may then be manually removed.

<FIG> is an exploded perspective view 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 <NUM> which are best viewed in <FIG> in association with the interior surface of the syringe mount socket <NUM>. Thus, a user may install a needle-free syringe <NUM> by sliding one or more orientation channels <NUM> over corresponding orientation guides <NUM> until the pawls <NUM> engage with the syringe grip surface <NUM>. 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. Referring back to <FIG>, 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 leading end of the socket <NUM> thereby providing visual confirmation that a syringe <NUM> is properly installed.

As noted above, it may be most 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 <NUM> sized to fit in fluid-tight engagement with the interior chamber of the syringe, thereby defining a fluid receiving dosage space <NUM> within a needle-free syringe <NUM>. As shown in <FIG>, the plunger system <NUM> includes a handle <NUM>. The handle <NUM> can be conveniently separated from the plunger body <NUM> at a break line <NUM> defined in a separable shaft <NUM> between the plunger body <NUM> and handle <NUM>. In use the handle <NUM> and separable shaft <NUM> 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 <NUM>, the trailing end of the plunger body <NUM> defines a hammer surface <NUM> which in use engages with the hammer <NUM> during an injection.

As shown in <FIG> and <FIG>, the interior portion of the syringe <NUM> defines a dosage space <NUM> within the interior walls of the syringe between the nozzle <NUM> and the plunger seal <NUM>. This dosage space <NUM> 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>. 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>. This particular configuration is illustrated in <FIG> and <FIG>.

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. It may also be noted that the leading edge of the hammer <NUM> includes a recess <NUM> which provides clearance for any extension or nub remaining beyond the hammer surface when the separable shaft <NUM> 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 <NUM> from the handle <NUM> at the break line <NUM>. Thus, during a remote filling operation, a user may insert the plunger body <NUM> and attached handle <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 <NUM>. The nozzle <NUM> may be placed in fluid communication with a supply of injectable material. The handle <NUM> 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 <NUM> and separable shaft <NUM> may then be removed at the break line <NUM> and the hammer surface102 and dose setting surface <NUM> made to be coplanar (thus precisely setting the selected dosage) by pressing upon the hammer surface <NUM> with the plunger positioning surface <NUM> of the handle. The foregoing operation may be performed while the nozzle <NUM> is continuously maintained in sterile fluid communication with an injectable substance supply, thus minimizing waste.

The remote filling of a needle-free syringe <NUM> may be facilitated by providing a filling adapter <NUM> as shown in <FIG>. The filling adapter <NUM> may include a male or female conical attachment surface <NUM> as illustrated in <FIG>. This conical attachment surface <NUM> is configured to mate with a corresponding male or female conical surface <NUM> positioned at the nozzle end <NUM> of a needle-free syringe <NUM> as shown in <FIG>. Thus, the corresponding male and female conical surfaces <NUM>, <NUM> form a fluid tight seal upon attachment of the filling adapter to the nozzle end of a syringe without the use of any separate compliant sealing member, an o-ring for example.

It may further be noted from <FIG> that the ergonomic use of the filling adapter <NUM> may be enhanced by providing stability wings <NUM> which provide a safe grip surface and substantially protect a filling needle <NUM> from contamination.

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 <NUM> of the syringe body. The cap <NUM> may be provided with an annular flange <NUM> at the closed end of the cap providing a stand surface with a diameter greater than the diameter of the open end of the cap body. In use, the stand surface may be employed to stand an array of filled needle-free syringes <NUM> upright in a ready position for engagement with a needle-free injection device <NUM>. Thus, if desired a needle-free syringe <NUM> may be loaded and ejected in an efficient hands free manner.

Also disclosed herein are methods of operating and filling a needle-free injector as described above. For example, one method includes providing a needle-free injection device <NUM> according to any one of the alternative arrangements described herein. The method further includes activating the activation button <NUM> to lock the inner housing <NUM> in the syringe loading position and subsequently loading a needle-free syringe <NUM> into the injector. An operator may then release the activation button <NUM> and move the inner housing <NUM> to the firing position by pressing the nozzle end <NUM> of the needle-free syringe <NUM> against the injection site with sufficient force. The injection may then be triggered by activating the activation button <NUM> when the inner housing is fully in the firing position. Optionally, the method may include steps of loading and ejecting a needle free syringe <NUM> from the device. Loading and ejection may occur without touching the syringe at any time.

One embodiment of the present invention is a method of filling a needle-free syringe <NUM> including providing a syringe having a nozzle <NUM> at one end and a dose setting surface <NUM> substantially opposite the nozzle <NUM>. The method further includes providing a plunger body <NUM> in sealed engagement with an inner surface of the syringe <NUM> where the plunger body <NUM> further comprises a hammer surface <NUM>. The filling method further comprises positioning the hammer surface <NUM> to be substantially coplanar with the dose setting surface <NUM>.

An alternative method of filling a needle-free syringe may include providing a filling adapter <NUM> with a filling needle <NUM> in sealed fluid communication with the nozzle <NUM> of the syringe body. A plunger system <NUM> including a handle <NUM> as described above may be placed into engagement with the syringe <NUM>. The plunger body <NUM> may then be moved forward to the nozzle end of the syringe body. The septum of storage vial of injectable fluid may be pierced with the filling needle <NUM>. The plunger system <NUM> is then withdrawn by the handle to a position where the break line <NUM> is beyond the dose setting surface <NUM>. The handle <NUM> is then removed from the plunger body <NUM> by separating the shaft <NUM> at the break line <NUM>. Next, the plunger body <NUM> may be moved toward the nozzle <NUM> by applying force against the hammer surface <NUM> with a plunger positioning surface <NUM> causing the hammer surface102 and dose setting surface <NUM> to become coplanar. Alternatively, the dose may be set by using a surface within the device, for example the leading edge of the hammer <NUM> to cause the hammer surface to become coplanar with the dose setting surface. Throughout the dose setting operation the filling adapter and needle-free syringe remain in direct fluid communication with the storage vial of injectable fluid, thereby allowing the precise setting of an injection dosage without the waste of any substantial amount of injectable fluid.

Claim 1:
A needle-free syringe system comprising:
a syringe body (<NUM>) comprising a nozzle (<NUM>) at one end and a dose setting surface (<NUM>) substantially opposite the nozzle (<NUM>); and
a plunger system (<NUM>) comprising a plunger body (<NUM>) comprising a leading end, a seal (<NUM>) and a hammer surface (<NUM>) substantially opposite the leading end, wherein the syringe body defines a dosage space (<NUM>) within the syringe between the nozzle (<NUM>) and the plunger seal (<NUM>), which dosage space (<NUM>) has a selected dosage volume when the plunger body is positioned within the syringe body such that the dose setting surface (<NUM>) and hammer surface (<NUM>) are co-planar; and
wherein the plunger system (<NUM>) further comprises:
a separable shaft (<NUM>) between the plunger body (<NUM>) and a handle (<NUM>), the handle being substantially opposite the plunger body (<NUM>); and
a break line (<NUM>) defined in the separable shaft (<NUM>), said break line providing for the handle (<NUM>) and separable shaft (<NUM>) to be removed from the plunger body (<NUM>).