before the present device and method are described , it is to be understood that this invention is not limited to particular embodiments described , as such may , of course , vary . it is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only , and is not intended to be limiting , since the scope of the present invention will be limited only by the appended claims . where a range of values is provided , it is understood that each intervening value , to the tenth of the unit of the lower limit unless the context clearly dictates otherwise , between the upper and lower limits of that range is also specifically disclosed . each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed within the invention . the upper and lower limits of these smaller ranges may independently be included or excluded in the range , and each range where either , neither or both limits are included in the smaller ranges is also encompassed within the invention , subject to any specifically excluded limit in the stated range . where the stated range includes one or both of the limits , ranges excluding either or both of those included limits are also included in the invention . unless defined otherwise , all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs . although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention , the preferred methods and materials are now described . all publications mentioned herein are incorporated herein by reference to disclose and describe the methods and / or materials in connection with which the publications are cited . it must be noted that as used herein and in the appended claims , the singular forms “ a ”, “ an ”, and “ the ” include plural referents unless the context clearly dictates otherwise . thus , for example , reference to “ a storage means ” includes a plurality of such storage means and reference to “ the spring ” includes reference to one or more springs and equivalents thereof known to those skilled in the art , and so forth . the publications discussed herein are provided solely for their disclosure prior to the filing date of the present application . nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention . further , the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed . the embodiments of the invention disclosed are based on aradigm &# 39 ; s ( formerly weston medical &# 39 ; s ) intraject needle - free injector , described in wo 95 / 03844 . fig1 presents a longitudinal section through the intraject needle - free injector prior to integration with the device of the present invention . in fig1 , the injection force is provided by a compressed gas spring , which comprises a cylinder 1 enclosed at one end containing a gas , typically nitrogen , typically at a pressure between 150 and 300 bar . contained within the cylinder is a dispensing member 2 . the end of the dispensing member has a frusto - conical , truncated cone - portion 3 and a flange 4 . there is a double o - ring seal 5 situated between the truncated cone section 3 and the flange 4 . prior to triggering the device , the dispensing member 2 is held in the position illustrated in fig1 by a latch 6 which sits in a groove in the dispensing member . the upper surface of the groove forms a cam surface 7 . consequently , there is force urging the latch to move to the left . in the configuration shown in fig1 , the latch is restricted from moving by the outer ring 8 . at the lower end of the cylinder 1 , there is an outwardly directed flange 9 . the cylinder is held in place by crimping the flange 9 to another outwardly directed flange 10 on the upper end on a coupling 11 . the sleeve 8 consists of an upper sleeve portion 12 within which the cylinder is situated , and a lower sleeve portion 13 . the lower sleeve portion 13 is connected to the coupling 11 by inter - engaging screw threads 14 formed on the inner and outer walls of the lower sleeve portion 13 and the coupling respectively 11 . the injector has a cartridge 15 which contains the medicament . in the cartridge there is a piston 16 , slidingly and sealingly located therein . the piston 16 may comprise a cylindrical portion containing two larger diameter ribs , and a frusto - conical portion . the piston 16 is in contact with the medicament 17 and at the other end of the cartridge 15 there is a discharge orifice 18 . adjacent to the orifice 18 there is an interface seal 19 contained within a seal carrier 20 . the interface seal 19 is required for filling the needle - free device as described in pct / gb9700889 . a stopper 20 a seals the medicament into the capsule . seal 19 , seal carrier 20 , and stopper 20 a , comprise the cap that must be removed prior to delivery . to place the device in the ready to deliver state , the cap must be snapped off at the frangible joint 21 . this removes the seal 19 and exposes the orifice 18 . the trigger blocking mechanism 22 , which prevents the medication cartridge from moving back toward the upper sleeve portion 22 , thereby preventing delivery , is removed . finally , latch 6 must be moved from the first ( safe ) position , to the second ( ready to deliver ) position , the latch 6 is incorporated into a groove in the dispensing member 2 — not only does the groove have a cam surface 7 but also a locking surface 27 which is perpendicular to the dispensing member axis and is located radially inward of the cam surface 7 . additionally , to access the latch 6 there is an opening 28 in the upper sleeve 12 , which prior to triggering is aligned with the latch 6 . fig2 a , b and c illustrate the operation of the safety mechanism . when the latch and dispensing member are initially assembled , the latch occupies the first ( safe ) position , as shown in fig2 a . in this position , the dispensing member - engaging latch portion 29 is acted on by the locking surface 27 . frictional force ensures that the latch is held rigid by the locking surface — typically the dispensing member exerts a force of at least 100n . the latch is placed in the second ( ready to deliver ) position using a pin which fits through opening 28 to push the latch in the direction of the arrow p into the position shown in fig2 b , ( and in fig1 ). in this position the dispensing member engaging latch portion 29 is in contact with the radially inner end of the cam surface 7 . to cause delivery , the orifice 18 is then placed against the skin of the patient . practically , this involves holding the device by the upper sleeve 12 portion . the upper sleeve 12 is then moved downwards with respect to the lower sleeve 13 , bringing aperture 25 in the wall of the upper sleeve portion 8 into alignment with the latch 6 . the latch then moves to the left into the aperture 25 , under the force exerted on it by the cam surface 7 formed in the dispensing member 3 into the position shown in fig2 c . the injector then delivers . it is advantageous to have a mechanism that places the device in the ready to deliver state in a simple motion or motions . fig3 illustrates one embodiment of the combined needle - free injector plus means for disengaging the safety mechanism 30 . in this figure , the means for disengaging the safety mechanism consists of a cap 31 enclosing , and holding rigidly , the seal carrier 20 , a lever 32 and a collar 33 . the lever 32 and collar 33 are presented in more detail in fig4 a and 4 b . the lever contains a lip 34 at the far end , over which the cap 31 is positioned . this ensures that the lever 32 cannot be moved before the outer cap 31 is removed , which in turn ensures that the user cannot move the latch or disengage the safety mechanism until the cap has been removed . the lever 32 is pivoted around the pivot axis 35 , with the pivoted surface in contact with injector being a cam surface 36 . the force required to pivot lever 32 is in the range from about 2n to about 30n . the collar 33 contains a pin 37 which extends into the device through the opening 28 in the upper sleeve 12 to impinge on the far side of the latch 6 , see fig4 a . the force required to move the latch is in the range from about 20n to about 120n . to stop the upper sleeve section 12 moving with respect to the lower sleeve section 13 , there are block sections 38 between the upper and lower sleeves , which form part of the collar 33 . the relative position of the block sections 38 with respect to the lever 32 is more clearly presented in the end - on view of the device shown in fig5 a . to deliver the device contents , the cap 31 is removed , exposing the injection orifice 18 . with the outer cap 31 removed , the lip 34 is exposed , enabling the lever 32 to rotate about the pivot axis 35 . only when the outer cap 31 is removed can the lever 32 be rotated . as the lever 32 rotates , the cam surface 36 forces the collar 33 to move in the direction q in fig3 , 4 a and 5 b pushing the pin 37 against the latch 6 . when the lever 32 has rotated through a complete cycle , approximately 180 ° as shown in fig4 b , the latch 6 moves to the second position , as shown in fig2 b . the blocks 38 no longer restrict the movement of the upper sleeve 12 with respect to the lower sleeve 13 and the device can trigger as described above . the relative movement of the block 38 with respect to the sleeve section 12 and 13 is seen in the end on view presented in fig5 b . by integrating the cap 31 to the lever 32 with a flexible joint at the tip 34 , the mechanism can also be configured to ensure that the user removes the stopper and sets the safety in a single action . fig9 shows an alternate embodiment from fig3 wherein rather than using the blocks 38 , the movement of the lever 32 exposes a trigger button 42 , the trigger button 42 subsequently being pressed by the subject to delivery the medication . another embodiment of the invention is shown in fig6 a , b and c . in fig6 a the as - received device is presented . to operate the device the outer cap 31 is removed , leaving the seal carrier 20 intact . the outer cap 31 is then inverted and placed back over the seal carrier 20 , as shown in fig6 b . pressure is then applied to the outer cap 31 to break the frangible seal between the seal carrier and the lower sleeve , as shown in fig6 c . the device is then placed in the ready to deliver state by rotating the lever 32 as described above and presented in fig4 a and b . a third embodiment of the invention is shown in fig7 a , b and c . this version of the attachment for disengaging the safety mechanism consists of an outer cap 31 covering and holding rigid the seal carrier 20 — not shown in fig7 a -, a collar section 39 and a barrel section 40 . the needle - free device fits within the barrel section 40 upper sleeve portion 12 first , so that the longitudinal axis of the device is aligned with the longitudinal axis of the barrel section 40 . the needle - free device is held rigidly within the barrel section 40 . the collar section 39 fits over and is attached to the barrel 40 , so that the collar section 39 is free to rotate about the axis of the device in a clockwise direction when the outer cap 31 has been removed . the outer cap 31 contains a locking mechanism 41 which locks the collar 39 rigid when the cap 31 is in place . to trigger the device the outer cap 31 is removed , which in turn removes the seal carrier 20 , exposing the injection orifice 8 . the collar section 39 is now free to rotate clockwise about the axis of the needle free device . because the cap 31 is locked into the collar section 39 , this ensures that the user cannot move the latch or disengage the safety mechanism until the cap has been removed so forcing the user to prepare the device in the correct order . there is a lip 42 on the collar section 39 , which is aligned so that the lip fits under the lip of the tear - off band 22 . as the collar section rotates clockwise the tear - off band 22 is torn off , so that after a complete revolution , 360 °, the tear - off band 22 is completely removed . simultaneously the safety mechanism is disengaged . this is illustrated by the cross - sections through the collar section shown in fig8 a and b . in fig8 a the safety mechanism is engaged — that is the latch is in the safe position shown in fig2 a . on the inside of the collar section there is a pin 37 which extends into the device through the opening 28 in the upper sleeve 12 to impinge on the far side of the latch 6 . the pin is in contact with the inner surface of the collar section . the inner surface of the ring section is a cam surface 43 , so that as the collar rotates the action of the cam surface pushes the pin against the latch moving the latch from the safe position to the first position as shown in fig8 b . with the tear - off band 22 removed , the device can deliver as outlined above . the preceding merely illustrates the principles of the invention . it will be appreciated that those skilled in the art will be able to devise various arrangements which , although not explicitly described or shown herein , embody the principles of the invention and are included within its spirit and scope . furthermore , all examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art , and are to be construed as being without limitation to such specifically recited examples and conditions . moreover , all statements herein reciting principles , aspects , and embodiments of the invention as well as specific examples thereof , are intended to encompass both structural and functional equivalents thereof . additionally , it is intended that such equivalents include both currently known equivalents and equivalents developed in the future , i . e ., any elements developed that perform the same function , regardless of structure . the scope of the present invention , therefore , is not intended to be limited to the exemplary embodiments shown and described herein . rather , the scope and spirit of present invention is embodied by the appended claims .