MXPA01001812A - Needleless injectors - Google Patents

Abstract

A pressurised gas powered actuator comprising a piston (3) operating in a cylinder (1). The stroke of the piston (3) may be reduced by uncovering one or more holes (14, 20) in the cylinder wall to permit the escape of the pressurised gas at a predetermined position along the swept wall of the cylinder. Alternatively, the piston (401) may be connected to a rod (402) which has a gas vent (406) formed therein, the position of the rod (402) with respect to the piston (401) being variable to adjust the stroke of the piston (401).

Description

INJECTORS WITHOUT NEEDLE Field of the Invention This invention relates to needleless injectors.

BACKGROUND OF THE INVENTION In International Patent Publication No. WO 95/03844, a needleless injector is disclosed. This is used to deliver liquid medications through the skin of a patient by means of a high-pressure jet of medication, generated by a piston pump. The energy to operate the pump can be derived from a coil spring, a pyrotechnic charge, hydraulic pressure or pressurized gas. The injectors are available through the use of different types of energy and the energy can be supplied by the user, for example, when a spring is manually compressed and latched to temporarily store the energy until it is required to "turn on" the injector. Alternatively, the injector can be supplied having the energy already stored - for example, by means of a pre-compressed spring or a pyrotechnic charge. It is proposed to dispose of some injectors after a single use, while others have a rechargeable energy storage medium and a disposable medication cartridge and there are many combinations to suit particular applications and markets. For the purposes of the present disclosure, the term "actuator" will be used to describe the energy storage and release mechanism, whether or not it is combined with the drug cartridge. In all cases, it is necessary to apply sufficient force at the end of the piston stroke to supply all the medication at the required pressure: if a spring is used, this is called "pre-loading". There is a need to supply different volumes of medication according to age, weight of the patient and factors in relation to the condition being treated and some single-use injectors, such as that described in EU-A-491 3699 ( Parsons), may be able to supply different volumes because the user must first fill the injector by using a cooperative drug transfer device, through which the medication is transferred from a bulk storage container to the cartridge of the injection. In this way, the user is able to vary the volume of filling and therefore the volume supplied. However, these injectors, although superficially simple, require the use of the transfer device, which is complicated and difficult to sterilize, and the aseptic transfer of the drug is almost impossible to achieve on a daily basis. Furthermore, for the knowledge of the current inventors, no prior art is known to use individual injectors, which have an actuating mechanism to vary the energy release in order to adjust the quantity to be administered. There are more complex reusable injectors such as those sold by the MediJect Corporation, in which the actuator can be adjusted to vary the energy release, but these also suffer most of the same fundamental problems as the Parson injector. A preferred embodiment in WO 95/03844 is a helical spring energized injector having adjustments for the delivered volume, but even this improvement over the prior art is somewhat complicated to process and operate. Other modalities in that application describe actuators energized by gas spring. (A gas spring comprises a cylinder and a piston, with pressurized gas that drives the piston temporarily constricted by a latching mechanism). A gas spring has several advantages over a coil spring: in particular, a much higher energy storage density is possible and at the end of the piston stroke the waste gas can be easily released through an opening in the cylinder wall. This last point is important to ensure safe disposal of the injector after use. In the case of a coil spring energized actuator, it would require a complicated mechanism to automatically discharge the residual energy stored in the dock at the end of its run. Although needleless injectors have great potential in reducing pain and fear of needles and in reducing cross infection, their high cost compared to a conventional syringe has mitigated against the spread of their use and this happens particularly in relation to the injectors that are required to supply a variable dose.

BRIEF DESCRIPTION OF THE INVENTION According to the present invention, there is provided an actuator for a gas-powered needle-free injector, comprising a driving member movable through a stroke to cause a substance to be supplied by the injector; means for creating a gas pressure in the drive member so as to cause it to move through the stroke; means for venting the gas pressure after the drive member has traveled through its stroke; and means for adjusting the effective location of the ventilation means, thus adjusting the stroke.

BRIEF DESCRIPTION OF THE INVENTION A particularly preferred embodiment is an actuator employing a gas spring, as described above, but having a stroke that is easily adjustable in small increments. This is achieved by having a series of valves along the cylinder, so that when a particular valve is opened, the pressurized gas drives the piston leaks rapidly through the valve, causing the piston to stop. Although the piston has certain moments in a gas-quenched system, which is a needleless injector, the absorption of energy and friction will reduce any over-travel in negligible proportions. In a first embodiment, a cylinder closed at one end contains a piston that seals and slides against the internal surface of the cylinder. The pressurized gas is contained between the closed end of the cylinder and the piston and urges the piston towards the open end of the cylinder. The movement of the piston is temporarily limited by a hook, operable by a cooperative sliding activating sleeve. A series of holes longitudinally aligned in the wall of the cylinder between the sealed part of the piston and the open end of the cylinder is covered and sealed by a sleeve slidable on the outside of the cylinder. By longitudinally moving the sleeve the holes can be progressively uncovered, so that when the hook operates to release the piston, the piston travels in the bore of the cylinder towards the open end, until the sealed part of the piston passes an open hole , after which the pressurized gas quickly escapes through the hole and the piston stops quickly. The sliding sleeve has a trigger or ratchet to allow the user to pre-fix the sleeve accurately before turning on the actuator. In a second embodiment, an actuator is provided comprising a piston and a cylinder as previously described, but having the sliding sleeve helically movable along the outside of the cylinder. In this embodiment, the holes through the cylinder wall can also be placed on a helical centerline, so that smaller adjustment increments are possible. In still another embodiment, the piston is connected to a vent member, preferably a rod, which has a valve formed therein, the position of the rod with respect to the piston being variable to adjust the stroke of the piston.

In all embodiments it is desirable that the position of the adjustment means be identified to allow the user to pre-fix the dose. The shortening effect of the stroke of the piston is to reduce the volume of medicament supplied from the drug cartridge, because the piston within the medicament cartridge will also have its stroke reduced. This way, there will be some remaining medication in the cartridge at the end of the injection. For most medicines this is not important and, in any case, pharmaceutical bottles normally contain an excess of the required drug. Although a gas spring is preferred, it is alternatively possible for the gas pressure to be created by a vaporizable gas or liquid container installed to apply gas pressure to the actuating member after the operation of the actuator.

BRIEF DESCRIPTION OF THE DRAWINGS The details of the preferred embodiments of the invention will now be described with reference to the following drawings: Figure 1 shows a longitudinal section through a first embodiment of a gas-powered actuator for a needleless injector, which It uses a longitudinal sliding sleeve to adjust the stroke of the piston. (Attention is drawn to International Patent Publication No. WO 97/37705 which is incorporated herein by reference, for a complete description of the injector and its operation).

Figures 2 and 3 are details of a trigger cooperating with the sliding sleeve, used in the first embodiment; Figure 4 shows part of the exterior of the first embodiment that includes a dose indicator; Figure 5 is a longitudinal section through part of a second embodiment, before ignition, having rotary means for adjusting the dose; Figure 6 shows the actuator of figure 5 after ignition; Figure 7 shows a gas cylinder forming part of the second embodiment, with a helical thread for its clutch with an adjustment projection; Figure 8 is a perspective view of the second embodiment, showing in particular the adjustment projection and the dose marking; Figures 9 to 11 show a third embodiment, with Figures 9 and 10 showing the actuator set for two different doses, before lighting, and Figure 11 shows the actuator after lighting; and Figure 12 shows a fourth mode, after power-up.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Figure 1, the actuator comprises a gas cylinder 1 closed at one end and having an opening at the other end defined by a flange 2. A piston 3 is a sliding fit in the cylinder 1 and it contains a seal 4 in sliding contact with the inner wall of the cylinder. Referring also to Figure 3, the actuator may be provided with a coupling 5, which has a thread 6 for connecting it to a drug cartridge 30 having a cooperative thread. The cartridge has a piston 31 slidably received therein and an outlet port 32, and between the piston 31 and the orifice 32 is filled with a substance 33 to be supplied by the injector, for example, a medicament in liquid form. The lower end of the cartridge is sealed by a member 34 that can break into a brittle connection 35 before being used. One or more terminals 7 are engaged in the flange 2 of the gas cylinder 1 to retain it. Between its closed end and seal 4 the gas cylinder is filled with pressurized gas or a mixture of pressurized gas and vaporizable liquid to provide additional pressurized gas. This drives the piston 3 in the direction of the arrow W. The piston 3 is temporarily limited by a hook 9 which reacts against a support face 1 0 on a coupling 5. The hook 9 is engaged with a cam face 1 1 in the piston 3, so that the force in the piston in the direction of the arrow W produces a lateral impulse in the hook 9 in the direction of the arrow Z. This has the effect of trying to disengage the hook 9 of the piston 3, thus igniting the actuator, but this action is prevented by the inner wall of an operating sleeve 1 2. When the operating magnet 1 2 moves in the direction of the arrow W relative to the assembly of the gas cylinder 1 and the coupling 5, an opening 1 3 in the wall of the operating sleeve 1 2 is juxtaposed with the hook 9, allowing the hook 9 to disengage from the piston 3. This is the operating principle which is more fully described in FIG. International Patent Publication No. WO 97/37705, incorporated herein by reference, but it is alternatively possible to employ other activating mechanisms designed for a specific extension. After the disengagement of the hook, the piston 3 hits the piston 31, causing the latter to supply a dose of the substance 33 through the orifice 32. Referring particularly to Figure 2, the cylinder 1 has a series of valve orifices 14 located in a row that is They extend longitudinally and perforate the wall of the cylinder 1. (The positions of the holes are also indicated in figure 1, in the piston 3). A valve sleeve 1 5 is slidable along the outside of the cylinder 1, and also makes the sealing of the contact with the holes reasonable. A ratchet 17 at the lower end of the valve sleeve 1 5 is engaged with a trigger 1 6 which is engaged together with the cylinder 1 by terminals 7 in the coupling 5. In this way, by sliding the valve sleeve 15 in the direction of the arrow S relative to the assembly of the cylinder 1 and the coupling 5, the sleeve of the valve 1 5 can move increasingly to increase the number of holes 14 in the wall of the gas cylinder 1 that is discovered, but not vice versa. Of course, if a one-way adjustment is not required, then the shape of the teeth of the trigger 16 and the pawl 17 can be changed to provide a ratchet function only. The orifice of the highest part 14a in the wall of the cylinder 1 can be used to fill the cylinder 1 with compressed gas. The piston is first placed in the cylinder 1 so that the seal 4 is just below the hole 14a (below as in the orientation of the drawings) and the pressurized gas 8 is introduced through the orifice 14a in the space between the seal 4 and the closed end of the cylinder 1. The piston 3 is further pushed into the cylinder 1 until the hook 9 can be engaged in the groove 1 8 in the piston 3. With the trigger disengaged by a suitable tool, the valve sleeve 1 5 is pushed towards the position shown in FIG. Figure 1 so that all holes 14 are sealed except for hole 14b. If the user then operates the actuator by operating an operating sleeve 12, at the end of the stroke of the piston the seal 4 passes the orifice 14b and the residual pressurized gas 8 escapes through the orifice 14b. However, if the sleeve has been previously adjusted to a certain intermediate position, then when the seal 4 passes the hole of the highest part without covering, the gas 8 will escape through that hole and the piston 3 will stop. Figure 4 shows the exterior of part of the actuator and illustrates the manner in which the valve sleeve 1 5 may have an operative protrusion 1 9 which may also serve as a dose indicator against the markings on the outside of the operation sleeve 12. Figures 5-8 show an actuator of similar construction but having rotary means for varying the stroke. In this embodiment, the holes 20 are installed in a helix to give minor increments of the stroke adjustments (but can be installed in a linear manner as in the first embodiment). The valve sleeve 1 5 terminates in a projection 22 and the interior of the sleeve 15 has a female threaded neck, which cooperates with a male threaded neck 21 in the gas cylinder 1. The threaded collars 21 can be a separate part that sinks or engages in the cylinder 1. The rotary movement of the valve magulite 15 moves to a linear movement and progressively discovers the holes 20. When the actuator is operated, the stroke of the piston 3 ends in the highest open hole 20 when the gas escapes through said orifice . A third embodiment of the invention will now be described with reference to figures 9 to 11. Referring first to Figure 9, a ram 401 is attached by threaded collars 403 to a hollow adjusting rod 402 and the ram and rod are assembled in a gas cylinder 409. Cylinder 409 contains pressurized gas 414, such as nitrogen, or a mixture of pressurized gas and vaporizable liquid, which is prevented from escaping by a water seal 41 0 and a rod seal 405, the latter sealingly joining the gas cylinder 409. The assembly of the ram 401, the seal 410 and the rod 402 is free to sliding longitudinally in the bore of the cylinder 409 and, consequently, the pressurized gas drives the ram 401 in the direction of the arrow A. The movement of the ram is temporarily prevented by a hook (not shown) engaged in a slot 41 3 , operable by an activating release mechanism configured to suit the application (not shown). The rod 402 is hollow and has a seal 404 sealingly assembled therein to prevent escape of the pressurized gas 414 through the hollow rod 402 via the threads 403. A hole 406 pierces the wall of the hollow adjustment rod 402 and the perforation of the hollow adjusting rod 402 is opened to the atmosphere at 416. The assembly of the cylinder 409 and the ram 402 is housed inside the sleeve 415. An adjustment projection 407 is free to rotate at the end of the sleeve 41 5 and is retained therein by a stop 41 2. Part of the rod 402 deforms to form a key 408 which is free to slide into a cooperative slot in the projection 407. In this way, when the projection 407 rotates , the rod 402 _ rotates with it, and the rod 402 will be screwed or unscrewed from the ram 401.

The ram is prevented from rotating with the rod 402 by the activating hook or other locating means or alternatively the friction of the seal 410 in the perforation of the cylinder 409 may be sufficient to prevent rotation. Referring to Figure 10, the rotation effect of the adjustment projection 407 can be observed, ie, the rod 402 is further screwed in the ram 401 and the hole 406 is closer to the seal 405. The ram stroke is indicated by the position of the graduations 41 1 in relation to the end face of the adjustment projection 407. Referring to Figure 11, the hook has been disengaged from the activating slot 413 in the ram 401, allowing the pressurized gas 414 move the ram and rod assembly in the direction of the arrow A When the orifice 406 passes through the seal 405, it is introduced into the cylinder 409 and allows the pressurized gas to escape through the bore of the hollow adjustment rod and to the atmosphere through the open end at 416. Since there is now no available motive power for the gas, the ram stops almost immediately, depending on the flow velocity of the pressurized gas through s of the hole 406 and the perforation of the hollow rod 402. Therefore, when adjusting the position of the hole 406 relative to the seal 405, the stroke of the ram and hollow rod assembly may vary. Figure 12 shows a fourth embodiment in an operated position corresponding to Figure 1 1 for the third embodiment. The fourth embodiment is similar to the third, but in this case a solid rod 402a replaces the previously described hollow rod and the orifice 405 is replaced by a deflection groove or horizontal reef 416a. When the rod 402a is in the position shown, the pressurized gas 414 escapes through the diverting slot 416a into the atmosphere through the valve 417. The above examples show that the addition of a few components to a single energized actuator by gas, can provide a stroke adjustment together with the safe escape of residual pressurized gas at the end of the drive.

Claims (16)

1. CLAIMS 1. An actuator for a gas-powered needle-free injector, characterized in that it comprises a drive member movable through a stroke to cause a substance to be supplied by the injector; means for creating a gas pressure in the driving member so as to cause it to move through the stroke; means for venting the gas pressure after the drive member has traveled through its stroke; and means for adjusting the effective location of the ventilation means, thus adjusting the stroke. An actuator according to claim 1, characterized in that the ventilation means comprises a plurality of ventilation openings installed at different distances along the stroke and the adjustment means comprises a member to determine which of the ventilation openings is the means of effective ventilation. An actuator according to claim 2, characterized in that said member of the adjustment means is a movable sleeve for selectively sealing or exposing the given ventilation openings. An actuator according to claim 3, characterized in that the ventilation openings are installed in a line parallel to the direction of movement of the actuating member. An actuator according to claim 3, characterized in that the ventilation openings are installed along a helical line. An actuator according to any of claims 3 to 5, characterized in that a plurality of possible locations for the sleeve are defined by a stop system. An actuator according to any of claims 3 to 5, characterized in that a plurality of possible locations for the sleeve are defined by a trigger system, by means of which the sleeve is movable in use in only one direction. An actuator according to any of claims 3 to 5, characterized in that the adjustment means includes a rotating projection, connected to a sleeve, and the adjustment means further comprises a threaded neck system for converting the rotary movement of the projection into linear movement of the sleeve. An actuator according to claim 1, characterized in that the ventilation means comprises a ventilation member movable with the actuating member and the adjustment means comprises means for adjusting the longitudinal position of the ventilation member with respect to the actuating member. An actuator according to claim 9, characterized in that the ventilation member is a hollow rod having a wall through which a ventilation opening extends, the longitudinal position of the hollow rod being adjustable so that at the end of the stroke of the actuating member, the gas pressure is vented through the ventilation opening and the inside of the rod hollows out. eleven . An actuator according to claim 9, characterized in that the vent member is a rod with a deflection formed therein, the longitudinal position of the rod being adjustable so that at the end of the stroke of the actuating member the pressure of the gas is vent through the deviation. An actuator according to any of claims 9 to 11, characterized in that the vent member is connected to the actuator member by a threaded neck and the adjusting means comprises means for rotating the vent member with respect to the actuator member for adjust the longitudinal position of the ventilation member with respect to the drive member. An actuator according to claim 12, characterized in that said vent member is longitudinally slidable with respect to said rotating means, whereby the actuating member is allowed to move longitudinally with respect to the rotary means during the stroke of the member drive. 14. An actuator according to any of the preceding claims, characterized in that the means for creating a gas pressure is a gas cylinder in which the actuator member is received for movement during its stroke, a latching device being provided to prevent movement of the actuator member before the operation of the actuator. actuator An actuator according to any of claims 1 to 1, characterized in that the means for creating a gas pressure is a vaporizable gas or liquid container installed to apply gas pressure to the actuating member after the operation of the actuator. An actuator according to any of the preceding claims, characterized in that the drive member is installed to strike a supply piston after the drive member has traveled part of its stroke and to cause, therefore, the supply piston to supply said substance of the injector, while the driving member completes its stroke.