referring to fig8 - 16 , there is illustrated a first embodiment of the invention . briefly , fig8 - 9 a illustrate a cannula / catheter introducer in the “ use ” position , while fig9 a - 11 illustrate the same introducer in the “ shoot back ” position . fig1 - 15 illustrate the valve which forms part of the catheter assembly and fig1 is a perspective view of the device attached to the catheter . referring initially to fig1 , there is illustrated a catheter introducer 10 which comprises an outer tube 11 . outer tube 11 contains a pair of finger gripping wings 12 . the front of outer tube 11 contains a number of step portions 13 to ultimately finish in an inlet 14 . a catheter assembly 15 can be attached to inlet 14 and assembly 15 includes a valve 16 to enable the flow from the catheter needle 17 to be regulated . fig1 - 15 illustrate particularly valve 16 . fig1 is a section view showing the valve in the “ off ” position and fig1 is a plan view showing the valve in the “ off ” position . fig1 - 15 illustrate similar views with the valve in the “ on ” position . the valve can be moved manually between the “ on ” position and the “ off ” position . referring now in greater detail to fig8 a and 8 b , there is illustrated details of the device 10 . briefly , the device functions to enable a contaminated needle 18 to be “ sucked ” back into the main body of the device after use thereby preventing needle stick injury . briefly , this is achieved by pushing the inner tube 19 forwardly relative to outer tube 11 by distance of only a few millimetres but this movement is sufficient to suck back a contaminated needle . this will now be described in greater detail . referring to fig8 a and 8 b , there is illustrated the device 10 attached to a catheter assembly 15 . device 10 has an outer tube 11 and an inner tube 19 with the inner tube 19 able to slide within outer tube 11 by a short distance ( typically a few millimetres ). outer tube 11 is cylindrical and can have a length of between 10 - 20 centimetres and a diameter of between 5 - 20 millimetres although no particular limitation should be placed on the invention merely by these dimensions . outer tube 11 will typically be made of suitable plastic material . outer tube 11 has a rear ( distal ) open end 20 to enable the inner tube 19 to be manipulated . the open end 20 contains an enlarged collar 21 which is best illustrated in fig8 b and which defines a small travelling passageway 22 of a few millimetres . inner tube 19 is under vacuum and has a closed rear ( distal ) end 23 . this distal end is formed with an annular rib 24 which is designed to move along passageway 22 . the annular rib 24 enables inner tube 19 to be moved forwardly ( or be pressed into outer tube 11 ) which will cause the annular rib 24 to move from the rear position illustrated in fig8 b to a forward position ( not illustrated ) but where rib 24 has been moved to adjacent the forward end of passageway 22 . initially , device 10 is in the position illustrated in fig8 a and 8 b . in this position , annular rib 24 is located within a pair of spaced apart internal beads 25 ( see fig8 b ) to provide a positive location of the inner tube 19 within the outer tube 11 , but which still enables a person to push the inner tube out of engagement with the beads 25 when required . referring to fig8 a , the forward part of outer tube 11 as mentioned above has a number of step portions 13 which terminate in an inlet 14 . inlet 14 is designed to attach to the rear of the catheter assembly 15 as is illustrated in fig8 . the puncture needle 18 ( see fig8 a ) is secured to a needle holder 26 of special design and which forms part of the shoot back mechanism which enables needle 18 to be shot back into the rear of inner tube 19 ( see fig1 and fig1 ). needle holder 26 is initially attached to outer tube 11 but can be detached therefrom as will be described in greater detail below . needle holder 26 contains a plurality of resilient fingers 27 . each finger 27 contains an outwardly extending rib 28 that extends into a corresponding recess on outer tube 11 . this engagement locks needle holder 26 to outer tube 19 and inside the stepped area 13 . the advantage of having a needle holder 26 initially locked to outer tube 11 is that there is very little chance that any rearward force on needle 18 will inadvertently release the needle holder prematurely . also , the needle will not move forwardly during the triggering operation . the resilient fingers 27 terminate in an arrowhead type configuration 29 and initially this part of the resilient fingers merely extends into the inside of outer tube 11 but is not attached to anything . the other part of the shoot back mechanism comprises an end member 30 . end member 30 is initially fitted to the open front ( proximal ) end of inner tube 19 and is best illustrated in fig8 a . end member 30 comprises a seal 31 which seals against the inside of inner tube 19 to maintain vacuum inside the inner tube . end member 30 is however prevented against being sucked back into inner tube 19 by a plurality of resilient fingers 32 . fingers 32 are biased to lock against the end of inner tube 19 ( see fig8 a ) and this arrangement prevents end member 30 from being sucked back into innertube 19 . the resilient fingers on end member 30 also have an arrowhead type configuration , but the arrangement is such that these resilient fingers are able to lock against the arrowhead configuration 29 on resilient fingers 27 which form part of needle holder 26 . however , this does not occur until such time as inner tube 19 is pushed forwardly . in use , a catheter assembly 15 can be fitted to the end of device 10 as illustrated in fig8 and fig1 . the catheter can then be inserted into a person &# 39 ; s vein . the puncture needle 18 becomes contaminated during this procedure . once the catheter assembly 15 is in place , the conventional technique of removing the puncture needle results in a needle stick risk . however , according to the present invention , once the catheter assembly is in place , a person can push inner tube 19 forwardly in a one - handed operation by grasping the wings 12 with the person &# 39 ; s fingers and using the person &# 39 ; s palm to push against end 23 of inner tube 19 . this causes rib 24 to push past the small locating beads 24 and along passageway 22 ( see fig8 b ). this forward movement ( only a few millimetres ) also causes the forward end of inner tube 19 to move towards the stepped portion 13 of outer tube 11 ( this being best illustrated between fig8 a and fig9 a ). this forward movement causes the arrowhead configuration on the end of fingers 32 to contact an internal tapering face 34 ( see fig9 a ) which causes the fingers 32 to be pushed inwardly . as this occurs , fingers 32 are released from the inner edge of inner tube 19 . as it is these fingers 32 that prevent end member 30 from being sucked back , as soon as the fingers are released , the end member will be sucked back into the distal portion of inner tube 19 . importantly , as fingers 32 are pushed inwardly and become released from the edge of inner tube 19 , they also engage behind the arrowhead formation of fingers 27 which form part of needle holder 26 . thus , as the fingers 32 are pushed inwardly , they lock against fingers 27 and this means that the end member 30 becomes locked to needle holder 26 . therefore , as end member 30 is sucked back into the distal end of inner tube 19 , it also drags back needle holder 26 and therefore the contaminated puncture needle 18 , this position being illustrated in fig1 and fig1 . the arrangement of having the needle holder 26 initially attached to outer tube 11 means that the puncture needle 18 exhibits no forward movement by virtue of any of the shoot back mechanism which forms part of the present invention . fig1 - 15 illustrate the turn valve on the catheter . the valve can turn manually between an open position and a closed position as illustrated in the figures . fig1 - 7 illustrate a second embodiment of the invention . this embodiment also uses vacuum to suck back the contaminated needle and is similar to the embodiment described with reference to fig8 - 16 . however , one difference is that instead of a two - part needle holder / end member arrangement which is described in the first embodiment , the second embodiment describes a single unit which in the second embodiment is called a needle holding piston assembly . one difference in the use of the second embodiment of the invention is that triggering the shoot back mechanism does result in the puncture needle moving forward by a few millimetres before being shot back into the inner tube . occasionally , this slight forward movement can create discomfort to a patient . the second embodiment ( fig1 - 7 ) provides a cannula / catheter introducer combination comprising a cannula and catheter assembly generally indicated by arrow 41 ( see fig7 ) and a retractable needle assembly generally indicated by arrow 42 for connection to the cannula / catheter combination . the cannula / catheter assembly 41 is provided with a valving member generally indicated by arrow 43 for controlling the ingress and egress of fluids from a patient . the cannula / catheter assembly is provided with a body 44 having an inlet 45 ( fig5 and 6 ) and an outlet 46 and the valving member intersects with a valve body 47 . the inlet 45 and outlet 46 respectively provide a needle aperture 48 and a slightly tapered socket 49 for connection with an outlet nozzle 50 ( see fig1 a ) of the needle assembly . the valving member 43 includes a valve plunger 51 which is adjustable from a first sealing position ( fig5 ) and a second flow position ( fig6 ). the plunger 51 has an aperture 52 therein supporting a resilient pierceable gasket 53 . the gasket 53 allows a puncture needle 54 to pass through it and when the needle is withdrawn it closes to seal off the needle penetration . the plunger is also provided with a peripheral fluted portion 55 which when positioned in the fluid mainstream 16 ( see fig6 ) allows fluid to pass in both directions . the retractable needle assembly 42 comprises outer and inner tubes 58 , 59 respectively ( see fig1 ) with the inner tube 59 being a sliding fit in the outer tube 58 . the outer tube 58 comprises a bore and has an open rear ( distal ) end 60 ( see fig1 b ) and is provided with forward finger gripping wings 61 . the front ( proximal ) end of the outer tube has a nozzle 50 that inserts into the socket 49 on the cannula / catheter . the inner tube 59 has a closed rear ( distal ) end 62 ( see fig1 b ) and an open front ( proximal ) end 63 ( see fig1 a ). a needle holding piston assembly 64 ( see fig1 a ) is a sliding fit within the inner tube 59 . the piston assembly 64 comprises a hollow tubular body 65 , which has an open front end and a closed rear end . the closed rear end has a mounting knob 69 . a sealing member 68 is mounted over the knob 69 . a needle mounting block 66 is fitted to the open front end of the body 65 . the piston assembly 64 includes a transparent vial section 70 , which enables medical staff to establish that the needle has been correctly inserted when blood flows to the vial and is visually detected . the open distal end 60 of the outer tube 58 ( fig1 b ) is provided with a shoulder 71 and the closed end 62 of the inner tube 59 has a complementary expanded portion 72 which ensures that the inner tube is secured within the outer tube . referring especially to fig1 b , it can be seen that this arrangement allows the inner tube to be pushed forwardly into the outer tube by a few millimetres , this distance being defined by the length of the recess 31 a ( which is a few millimetres ). the arrangement also ensures that the inner tube 59 cannot be readily pulled out of the outer tube 58 . this short stroke of a few millimetres is however sufficient to trigger the shoot back mechanism of the needle as will be described in greater detail below . the front end of the needle mounting block 66 is provided with a plurality of raked fingers 67 . these fingers are formed integrally with the needle mounting block and are resilient . the fingers are designed to lock against the front of inner tube 59 . the function of fingers 67 is to prevent the needle holding piston assembly 64 from moving along the inside of inner tube 59 from the proximal end of the inner tube ( see fig1 a ) to the distal end of inner tube ( see , for instance , fig3 and fig4 ). a vacuum is provided in inner tube 59 and seal 68 maintains the vacuum inside inner tube 59 . thus , there is a force acting on the needle holding piston assembly 64 to “ suck ” the needle holding piston assembly 64 back into inner tube 59 towards the distal end of the inner tube ; however the resilient fingers 67 lock against the front of inner tube 59 and prevent the needle holding piston assembly 64 from being sucked back . the arrangement described immediately above and illustrated in fig1 and fig1 a , is the initial position of the device . to dislocate the fingers 67 , the end 62 of the inner tube is pushed forward using the palm of the hand whilst gripping the wings 61 with the fingers . the fingers are thereby forced into the tapered section of the nozzle 50 and compressed to the extent that the needle assembly is withdrawn under vacuum , the situation illustrated by fig3 and 4 . more specifically , inner tube 59 can be pushed forwardly by a few millimetres in the manner described immediately above which moves the expanded portion 72 ( see fig1 b ) from the position illustrated in fig1 b , to a position ( not illustrated ) where the expanded portion is now at the other end of the recess 31 a . this short distance is sufficient to trigger the needle shoot back mechanism . specifically , and best illustrated in fig2 a , as the inner tube 59 is pushed forwardly by a few millimetres , it will push the needle holding piston assembly 64 forwardly by a few millimetres . as this occurs , the resilient fingers 67 push forwardly ( as they form part of the needle block 66 which is attached to the front of the needle holding piston assembly 64 ). the front part of outer tube 58 tapers inwardly ( see fig1 a ) and the resilient fingers 67 are arrow shaped in configuration which means that as the resilient fingers are pushed forwardly , they will be pressed inwardly ( see fig2 a ), and consequently they will dislodge from the front of inner tube 59 . as soon as the fingers 67 have been released from inner tube 59 , the vacuum inside inner tube 59 will suck back the needle holding piston assembly 64 thereby retracting the contaminated puncture needle 54 back into the body of inner tube 59 , this position being illustrated in fig3 and fig4 . the forward movement of inner tube 59 is limited by the arrangement illustrated in fig1 b , and also by a shoulder 73 ( see fig2 a ) on outer tube 58 . once the cannula / catheter device is secured and the needle assembly removed , the cannula / catheter can be used for the introduction or withdrawal of fluids to and from a patient . the arrangement is simple to use and , in practice , once the device has been inserted into the cannula assembly 41 , the inner tube 59 is pushed forwardly by just a few millimetres without any requirement to rotate the inner tube or use any separate locking mechanisms and upon forward pushing of the inner tube , the contaminated needle 54 is sucked back to the rear of inner tube 59 to render the contaminated needle 54 safe . it is not possible to push or otherwise enable the contaminated needle 54 to emerge from the safety of inner tube 59 . the arrangement is a simple one - handed reliable arrangement . fig1 and 2 of the drawings show the fully assembled device as delivered for use , fig3 of the drawings with the needle withdrawn after use , and fig4 separation of the cannula / catheter from the needle assembly . fig5 and 6 of the drawings show alternative positions of the plunger 51 of the valving member 43 . in fig5 , the plunger 51 is in a first position with the gasket 53 blocking fluid flow . in fig6 , the plunger 51 has been manually repositioned and the fluted portion 55 provides a passage for fluid flow . fig7 of the drawings is an assembly drawing of the device of the present invention in a ready - to - use condition . aspects of the present invention have been described by way of example only and modifications and additions thereto may be made without departing from the spirit or scope thereof .
a device is disclosed that allows a puncture needle to be inserted into a catheter . once the puncture needle has performed its function , it can shoot back into the device such that there is a reduce likelihood of needlestick injury . vacuum is used to assist in the shoot back function .