referring now to the drawings and first to fig8 - 19 which shows a first embodiment of a needle tip assembly . the needle tip assembly includes a needle tip cap 30 having various generally cylindrical portions with different diameters , a needle cap 40 , and a needle tip 50 . the proximal end 30 a of the needle tip cap 30 is closed while the distal end includes a circumferential flange 30 b . the proximal end 40 a of the needle cap 40 is closed while the distal end includes a circumferential flange 40 b . the proximal end of the needle tip 50 includes a needle n while the distal end includes an opening which is sized to allow the needle tip 50 to be mounted to the threaded proximal end 2 of the pen needle device 1 . in order to ensure that the needle tip 50 is prevented from being re - installed onto the proximal end 2 , the needle tip 50 utilizes a ring 60 which can move axially from an initial position ( see fig9 ) to a second position ( see fig1 ) which causes one or more inwardly deflecting members 50 a and 50 b to deflect inwards by an amount which is sufficient to prevent the needle tip 50 ( after being removed ) from being re - installed onto the proximal end 2 . as can be seen in fig8 , prior the needle tip assembly being installed onto the threaded proximal end 2 , the one or more inwardly deflecting members 50 a and 50 b are bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 to be installed onto the proximal end 2 in the conventional manner , i . e ., by axially sliding it on or by threading it on . as can be seen in fig9 , the needle tip assembly can be installed onto the threaded proximal end 2 without activating the re - use prevention mechanism , i . e ., without causing the ring 60 to move axially to the locked position . accordingly , in the position shown in fig9 , the one or more inwardly deflecting members 50 a and 50 b are still bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 to be installed onto the proximal end 2 in the conventional manner . furthermore , while the ring 60 is in the position shown in fig9 , the needle tip assembly can be removed in the conventional way by , e . g ., unthreading it off of the threaded end 2 . as can be seen in fig1 , after the needle tip assembly is installed onto the threaded proximal end 2 ( as shown in fig9 ), the needle tip cap 30 can be further moved axially in the distal direction ( as indicated by the arrow in fig1 ) to the point that it activates the re - use prevention system or mechanism , i . e ., it causes the ring 60 to move axially in the distal direction until it assumes the locked position . the locked position is characterized by engagement between the projections of the one or more inwardly deflecting members 50 a and 50 b and the inner circumferential recess of the ring 60 . accordingly , in the position shown in fig1 , the one or more inwardly deflecting members 50 a and 50 b have been deflected inwardly so that they are now biased against the proximal end 2 and frictionally engage the threads thereof when the needle tip 50 is unthreaded . furthermore , while the ring 60 is in the position shown in fig1 , the needle tip assembly can be removed , e . g ., in the conventional way by unthreading it off of the threaded end 2 , but , unlike the prior art , cannot thereafter be reinstalled . as can be seen in fig1 , once the needle tip assembly is installed ( fig9 ) and the re - use prevention system activated ( fig1 ), the needle tip cap 30 can be removed by sliding it off axially . then , as shown in fig1 , the needle cap 40 can be removed . fig1 shows the pen needle device with the installed needle tip 50 in a position that is ready for injection . again , in this position , the ring 60 has been moved to the locked position which has caused a plurality of inwardly deflecting members 50 a and 50 b to frictionally engage the threaded proximal end 2 of the pen needle device 1 . as can be seen in fig1 , once the pen needle device with the installed needle tip assembly has been used to perform an injection , the needle tip 50 can be removed in the following ways : one could simply grip the needle tip 50 in the area of the ring 60 and unthread it from the threaded proximal end 2 . this is risky , of course , because the user can be inadvertently be pricked by the exposed needle n ; one could re - install the needle cap 40 and then grip the needle tip 50 in the area of the ring 60 and unthread it from the threaded proximal end 2 ; one could re - install both the needle cap 40 and the needle tip cap 30 , and then grip the needle tip cap 30 in the area just in front of the flange 30 b and thereafter unthread the entire needle tip assembly thereby causing the needle tip 50 to become unthreaded from the threaded proximal end 2 ; and one could re - install only the needle tip cap 30 , and then grip the needle tip cap 30 in the area just in front of the flange 30 b and thereafter unthread the needle tip assembly ( without the cap 40 ) thereby causing the needle tip 50 to become unthreaded from the threaded proximal end 2 . all of these ways are contemplated by the invention , but the first way is the least desirable . as is evident from fig1 , once the needle tip 50 is removed from the threaded proximal end 2 ( and because the ring 60 has been moved to the locked position ), the plurality of inwardly deflecting members 50 a and 50 b are caused to move inwardly to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 back onto the threaded proximal end 2 of the pen needle device 1 . this is evident from fig1 which shows how the plurality of inwardly deflecting members 50 a and 50 b have been moved inwardly to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 back onto the threaded proximal end 2 of the pen needle device 1 owing to the fact that they effectively reduce the diameter of the distal opening of the needle tip 50 . as is evident from fig1 and 17 , the needle cap 40 has a closed proximal end 40 a , an open distal end having a circumferential flange 40 b , a distal opening 40 c sized to frictionally engage with a hub portion of the needle tip 50 , and a tapered portion 40 d which is sized to safely receive therein the needle n . of course , the needle cap 40 can have any desired configuration provided that it functions for its intended purpose , and can even be dispensed with without leaving the scope of the invention . as is evident from fig1 and 19 , the needle tip cap 30 has a closed proximal end 30 a , an open distal end having a circumferential flange 30 b , a distal opening 30 c sized to receive therein the ring 60 , a shoulder 30 c which engages with a distal end of the ring 60 so as to cause the ring 60 to move to the locked position , a generally circumferential surface 30 e which is sized to frictionally engage with an outer surface of the needle tip 50 so as to cause it to rotate relative to the proximal end 2 , and a tapered and / or stepped portion 30 f which is sized to safely receive therein the needle n and the needle cap 40 . of course , the needle tip cap 30 can have any desired configuration provided that it functions for its intended purpose , and can even be dispensed with without leaving the scope of the invention . in the later case , only the needle cap 40 ( or even one of the type shown in fig5 and 54 ) would need to be utilized ( for safety reasons ) and the user could activate the re - use prevention system by gripping the ring 60 and sliding it distally until it assumes the locked position . fig2 - 28 shows a second embodiment of a needle tip assembly . the needle tip assembly includes a needle tip cap 30 having various generally cylindrical portions with different diameters , a needle cap 40 , and a needle tip 50 ′. as the needle tip cap 30 , the needle cap 40 , and the ring 60 of the instant embodiment are essentially identical to those used in the previous embodiment , they have been accorded the same reference numerals . the proximal end 30 a of the needle tip cap 30 is closed while the distal end includes a circumferential flange 30 b . similarly , the proximal end 40 a of the needle cap 40 is closed while the distal end includes a circumferential flange 40 b . the proximal end of the needle tip 50 ′ includes a needle n while the distal end includes an opening which is sized to allow the needle tip 50 ′ to be mounted to the threaded proximal end 2 of the pen needle device 1 . in order to ensure that the needle tip 50 ′ is prevented from being re - installed onto the proximal end 2 , the needle tip 50 ′ utilizes a ring 60 which can move axially from an initial position ( see fig2 ) to a second position ( see fig2 ) which causes one or more inwardly deflecting members 50 ′ a and 50 ′ b to deflect inwards by an amount which is sufficient to prevent the needle tip 50 ′ ( after being removed ) from being re - installed onto the proximal end 2 . as can be seen in fig2 , prior the needle tip assembly being installed onto the threaded proximal end 2 , the one or more inwardly deflecting members 50 ′ a and 50 ′ b are bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 ′ to be installed onto the proximal end 2 in the conventional manner , i . e ., by axially sliding it on or by threading it on . as can be seen in fig2 , the needle tip assembly can be installed onto the threaded proximal end 2 without activating the re - use prevention system or mechanism , i . e ., without causing the ring 60 to move axially to the locked position . accordingly , in the position shown in fig2 , the one or more inwardly deflecting members 50 ′ a and 50 ′ b are still bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 ′ to be installed onto the proximal end 2 . furthermore , while the ring 60 is in the position shown in fig2 , the needle tip assembly can be removed in the conventional way , e . g ., by unthreading it off of the threaded end 2 . as can be seen in fig2 , after the needle tip assembly is installed onto the threaded proximal end 2 ( as shown in fig2 ), the needle tip cap 30 can be further moved axially in the distal direction ( as indicated by the arrow in fig2 ) to the point that it activates the re - use prevention system or mechanism , i . e ., it causes the ring 60 to move axially in the distal direction until it assumes the locked position . the locked position is characterized by engagement between the projections of the one or more inwardly deflecting members 50 ′ and 50 ′ and the inner circumferential recess of the ring 60 . accordingly , in the position shown in fig2 , the one or more inwardly deflecting members 50 ′ a and 50 ′ b have been deflected inwardly so that they are now biased against the proximal end 2 and frictionally engage the threads thereof when the needle tip 50 ′ is unthreaded . furthermore , while the ring 60 is in the position shown in fig2 , the needle tip assembly can be removed , e . g ., in the conventional way by unthreading it off of the threaded end 2 , but , unlike the prior art , cannot thereafter be reinstalled . as can be seen in fig2 , once the needle tip assembly is installed ( fig2 ) and the re - use prevention system activated ( fig2 ), the needle tip cap 30 can be removed by sliding it off axially . then , as shown in fig2 , the needle cap 40 can also be removed axially . fig2 shows the pen needle device with the installed needle tip 50 ′ in a position that is ready for injection . again , in this position , the ring 60 has been moved to the locked position which has caused a plurality of inwardly deflecting members 50 ′ a and 50 ′ b to frictionally engage the threaded proximal end 2 of the pen needle device 1 . as can be seen in fig2 and 27 , once the pen needle device with the installed needle tip assembly has been used to perform an injection , the needle tip 50 ′ can be removed in the following ways : one could simply grip the needle tip 50 ′ in the area of the ring 60 and unthread it from the threaded proximal end 2 . this is risky , of course , because the user can be inadvertently be pricked by the exposed needle n ; one could re - install the needle cap 40 and then grip the needle tip 50 ′ in the area of the ring 60 and unthread it from the threaded proximal end 2 ; one could re - install both the needle cap 40 and the needle tip cap 30 , and then grip the needle tip cap 30 in the area just in front of the flange 30 b and thereafter unthread the entire needle tip assembly thereby causing the needle tip 50 ′ to become unthreaded from the threaded proximal end 2 ; and one could re - install only the needle tip cap 30 , and then grip the needle tip cap 30 in the area just in front of the flange 30 b and thereafter unthread the needle tip assembly ( without the cap 40 ) thereby causing the needle tip 50 ′ to become unthreaded from the threaded proximal end 2 . as was the case in the previous embodiment , all of these ways are contemplated by the invention for this embodiment , with , however , the first way being the least desirable . as is evident from fig2 , once the needle tip 50 ′ is removed from the threaded proximal end 2 ( and because the ring 60 has been moved to the locked position ), the plurality of inwardly deflecting members 50 ′ a and 50 ′ b are caused to move inwardly to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 ′ back onto the threaded proximal end 2 of the pen needle device 1 . this is evident from fig2 which shows how the plurality of inwardly deflecting members 50 ′ a and 50 ′ b have been moved inwardly to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 ′ back onto the threaded proximal end 2 of the pen needle device 1 owing to the fact that they effectively reduce the diameter of the distal opening of the needle tip 50 ′. as is evident from comparing fig2 and 15 , the needle tip 50 ′ differs from the needle tip 50 in that it does not utilize any internal threads in the body of the needle tip 50 ′ ( i . e ., the distal opening which receives therein the threaded proximal end 2 is generally cylindrical and smooth ) and with regard to the shape of the projections which extend inwardly from the members 50 a / 50 ′ a and 50 b / 50 ′ b . that is , the projections which extend inwardly from the members 50 a and 50 b have a generally blunt end or rectangular - shaped cross - section whereas the projections which extend inwardly from the members 50 ′ a and 50 ′ b have a generally tapered end or triangular - shaped cross - section so as to threadably engage with the threads of the proximal end 2 . although not shown , the embodiment shown in fig2 - 28 can instead , like the previous embodiment , utilize the needle tip cap shown in fig4 - 49 . of course , the needle tip cap 30 can have any desired configuration provided that it functions for its intended purpose , and can even be dispensed with without leaving the scope of the invention . in the later case , only the needle cap 40 ( or even one of the type shown in fig5 and 54 ) would need to be utilized ( for safety reasons ) and the user could activate the re - use prevention system by gripping the ring 60 and sliding it distally until it assumes the locked position . fig2 and 30 show an optional needle tip 50 ″ which can be used with any of the embodiments disclosed herein . for purposes of clarity , the ring 60 has been removed . unlike the previous embodiments which utilize two oppositely arranged inwardly deflecting members 50 a / 50 ′ a and 50 b / 50 ′ b which are caused to move inwardly by the ring 60 , this embodiment utilizes four equally angularly spaced members 50 ″ a , 50 ″ b , 50 ″ c and 50 ″ d , which can be moved inwardly by the ring 60 to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 ″ back onto the threaded proximal end 2 of the pen needle device 1 owing to the fact that they effectively reduce the diameter of the distal opening of the needle tip 50 ″. although the members 50 ″ a , 50 ″ b , 50 ″ c and 50 ″ d are shown deflected inwardly ( for purposes of clarity ), of course this would not occur until the ring 60 has been moved to the locked position . the needle tip 50 ″, like the second embodiment , does not utilize any internal threads in the body of the needle tip 50 ″ ( i . e ., the distal opening which receives therein the threaded proximal end 2 is generally cylindrical and smooth ) and utilizes projections p which extend inwardly from the members 50 ″ a , 50 ″ b , 50 ″ c and 50 ″ d and have a generally tapered end or triangular - shaped cross - section so as to threadably engage with the threads of the proximal end 2 . the projections p can extend all the way across the width of each of the members 50 ″ a , 50 ″ b , 50 ″ c and 50 ″ d ( as shown in fig2 ) or they have other forms such as ones which are shorter than the width of the members 50 ″ a , 50 ″ b , 50 ″ c and 50 ″ d . the projections p may even have the form of centrally disposed circular or rounded projections . other configurations may also be utilized provided they are capable of locking with an / or frictionally engaging with the ring 60 . as is evident from fig3 and 32 , the ring 60 which can be used in the previous embodiments is generally cylindrical and has a proximal end 60 d which engages the shoulder 30 c of the needle tip cap 30 , a distal end having a tapered inner surface 60 c configured to facilitate sliding over the deflecting members 50 a / 50 b or 50 ′ a / 50 ′ b or 50 ″ a / 50 ″ b / 50 ″ c // 50 ″ d , a circumferential recess 60 a sized and configured to receive therein the projections p of the members 50 a / 50 b or 50 ′ a / 50 ′ b or 50 ″ a / 50 ″ b / 50 ″ c // 50 ″ d , and an inner cylindrical surface 60 b which is sized to slide over the needle tip body . of course , the ring 60 can have any desired configuration provided that it functions for its intended purpose . fig3 shows still another embodiment of a needle tip assembly . the needle tip assembly includes a needle tip cap 30 having various generally cylindrical portions with different diameters , a needle cap 40 , and a needle tip 50 iii . as the needle tip cap 30 and the needle cap 40 of the instant embodiment are essentially identical to those used in the previous embodiment , they have been accorded the same reference numerals . in this embodiment also , the proximal end 30 a of the needle tip cap 30 is closed while the distal end includes a circumferential flange 30 b . similarly , the proximal end 40 a of the needle cap 40 is closed while the distal end includes a circumferential flange 40 b . the proximal end of the needle tip 50 iii includes a needle n while the distal end includes an opening which is sized to allow the needle tip 50 iii to be mounted to the threaded proximal end 2 of the pen needle device 1 . in order to ensure that the needle tip 50 iii is prevented from being re - installed onto the proximal end 2 , the needle tip 50 iii utilizes a ring 60 ′ which can move axially from an initial position ( similar to the position shown in fig2 ) to a second position ( similar to the position shown in fig2 ) which causes the four inwardly deflecting members 50 iii a , 50 iii b , 50 iii c and 50 iii d to deflect inwards by an amount which is sufficient to prevent the needle tip 50 iii ( after being removed ) from being re - installed onto the proximal end 2 . as can be seen in fig3 , prior to the needle tip assembly being installed onto the threaded proximal end 2 ( not shown in fig3 ), the four inwardly deflecting members 50 iii a , 50 iii b , 50 iii c and 50 iii d are bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 iii to be installed onto the proximal end 2 in the conventional manner , i . e ., by axially sliding it on or by threading it on . in a manner similar to that shown fig2 , the needle tip assembly of fig3 can be installed onto the threaded proximal end 2 without activating the re - use prevention system or mechanism , i . e ., without causing the ring 60 ′ to move axially to the second or activated position . accordingly , in the position shown in fig3 , the one or more inwardly deflecting members 50 iii a , 50 iii b , 50 iii c and 50 iii d are still bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 iii to be installed onto the proximal end 2 . furthermore , while the ring 60 ′ is in the position shown in fig3 , the needle tip assembly can be removed in the conventional way , e . g ., by unthreading it off of the threaded end 2 . in the same way as was shown in fig2 , after the needle tip assembly shown in fig3 is installed onto the threaded proximal end 2 ( similar to that shown in fig2 ), the needle tip cap 30 can be further moved axially in the distal direction ( as indicated by the arrow in fig2 ) to the point that it activates the re - use prevention system or mechanism , i . e ., it causes the ring 60 ′ to move axially in the distal direction until it assumes the second or activated position . unlike the previous embodiments which provide for a locking position , i . e ., characterized by engagement between the projections of the inwardly deflecting members and the inner circumferential recess of the ring , this embodiment utilizes no projections on the members 50 iii a , 50 iii b , 50 iii c and 50 iii d and does not therefore utilize the recess for receiving the same on the ring 60 ′. instead , the ring 60 ′ merely frictionally engages with the outer surfaces of the members 50 iii a , 50 iii b , 50 iii c and 50 iii d when it is moved to the second or activated position . in order to ensure that the ring 60 ′ does not move back to the original position ( after being moved to the second position ), the inner circumferential surface of the ring 60 ′ and the outer surface of the members 50 iii a , 50 iii b , 50 iii c and 50 iii d can be provided with high friction surfaces such as e . g ., a knurl , a high friction coating , etc . although not shown , when the ring 60 ′ is moved to the second or activated position , the inwardly deflecting members 50 iii a , 50 iii b , 50 iii c and 50 iii d will be deflected inwardly ( as was the case in the previous embodiments ) so that they will biased against the proximal end 2 and frictionally engage the threads thereof when the needle tip 50 iii is unthreaded . as was the case in the previous embodiments , once the needle tip assembly shown in fig3 is installed and the re - use prevention system activated , the needle tip cap 30 can be removed by sliding it off axially . then , the needle cap 40 can also be removed axially . once the pen needle device with the installed needle tip assembly has been used to perform an injection , the needle tip 50 iii can be removed in the following ways : one could simply grip the needle tip 50 iii in the area of the ring 60 ′ and unthread it from the threaded proximal end 2 . this is risky , of course , because the user can be inadvertently be pricked by the exposed needle n ; one could re - install the needle cap 40 and then grip the needle tip 50 iii in the area of the ring 60 ′ and unthread it from the threaded proximal end 2 ; one could re - install both the needle cap 40 and the needle tip cap 30 , and then grip the needle tip cap 30 in the area just in front of the flange 30 b and thereafter unthread the entire needle tip assembly thereby causing the needle tip 50 iii to become unthreaded from the threaded proximal end 2 ; and one could re - install only the needle tip cap 30 , and then grip the needle tip cap 30 in the area just in front of the flange 30 b and thereafter unthread the needle tip assembly ( without the cap 40 ) thereby causing the needle tip 50 iii to become unthreaded from the threaded proximal end 2 . as was the case in the previous embodiments , all of these ways are contemplated by the invention for this embodiment , with , however , the first way being the least desirable . as was the case in the embodiment shown in fig2 - 28 , once the needle tip 50 iii is removed from the threaded proximal end 2 ( and because the ring 60 ′ has been moved to the activated position ), the plurality of inwardly deflecting members 50 iii a , 50 iii b , 50 iii c and 50 iii d are caused to move inwardly to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 iii back onto the threaded proximal end 2 of the pen needle device 1 . this occurs in substantially the same way as was shown in fig2 which shows how the plurality of inwardly deflecting members have been moved inwardly to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 iii back onto the threaded proximal end 2 of the pen needle device 1 owing to the fact that they effectively reduce the diameter of the distal opening of the needle tip 50 iii . although not shown , the embodiment shown in fig3 can , like the previous embodiments , utilize the needle tip cap shown in fig4 - 49 instead of the needle tip cap 30 shown in fig3 . of course , the needle tip cap 30 can also have any desired configuration provided that it functions for its intended purpose , and can even be dispensed with without leaving the scope of the invention . in the later case , only the needle cap 40 ( or even one of the type shown in fig5 and 54 ) would need to be utilized ( for safety reasons ) and the user could activate the re - use prevention system by gripping the ring 60 ′ and sliding it distally until it assumes the activated position . fig3 shows still another embodiment of a needle tip assembly . the needle tip assembly includes a needle tip cap 30 having various generally cylindrical portions with different diameters , a needle cap 40 , and a needle tip 50 ii of the type shown in fig2 and 30 . as the needle tip cap 30 and the needle cap 40 of the instant embodiment are essentially identical to those used in previous embodiments , they have been accorded the same reference numerals . in this embodiment also , the proximal end 30 a of the needle tip cap 30 is closed while the distal end includes a circumferential flange 30 b . similarly , the proximal end 40 a of the needle cap 40 is closed while the distal end includes a circumferential flange 40 b . the proximal end of the needle tip 50 ii includes a needle n while the distal end includes an opening which is sized to allow the needle tip 50 ii to be mounted to the threaded proximal end 2 of the pen needle device 1 . in order to ensure that the needle tip 50 ii is prevented from being re - installed onto the proximal end 2 , the needle tip 50 ii utilizes a ring 60 ′ which can move axially from an initial position ( similar to the position shown in fig2 ) to a second position ( similar to the position shown in fig2 ) which causes the four inwardly deflecting members 50 ii a , 50 ii b , 50 ii c and 50 ii d to deflect inwards by an amount which is sufficient to prevent the needle tip 50 ii ( after being removed ) from being re - installed onto the proximal end 2 . as can be seen in fig3 , prior to the needle tip assembly being installed onto the threaded proximal end 2 ( not shown in fig3 ), the four inwardly deflecting members 50 ii a , 50 ii b , 50 ii c and 50 ii d are bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 ii to be installed onto the proximal end 2 in the conventional manner , i . e ., by axially sliding it on or by threading it on . in a manner similar to that shown fig2 , the needle tip assembly of fig3 can be installed onto the threaded proximal end 2 without activating the re - use prevention system or mechanism , i . e ., without causing the ring 60 ′ to move axially to the second or activated position . accordingly , in the position shown in fig3 , the one or more inwardly deflecting members 50 ii a , 50 ii b , 50 ii c and 50 ii d are still bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 ii to be installed onto the proximal end 2 . furthermore , while the ring 60 ′ is in the position shown in fig3 , the needle tip assembly can be removed in the conventional way , e . g ., by unthreading it off of the threaded end 2 . in the same way as was shown in fig2 , after the needle tip assembly shown in fig3 is installed onto the threaded proximal end 2 ( similar to that shown in fig2 ), the needle tip cap 30 can be further moved axially in the distal direction ( as indicated by the arrow in fig2 ) to the point that it activates the re - use prevention system or mechanism , i . e ., it causes the ring 60 ′ to move axially in the distal direction until it assumes the second or activated position . unlike the previous embodiments which provide for a locking position , i . e ., characterized by engagement between the projections of the inwardly deflecting members and the inner circumferential recess of the ring , this embodiment utilizes projections on the members 50 ii a , 50 ii b , 50 ii c and 50 ii d , but does not utilize the recess for receiving the same on the ring 60 ′. instead , the ring 60 ′ merely frictionally engages with the projections of the members 50 ii a , 50 ii b , 50 ii c and 50 ii d ( thereby causing the members 50 ii a , 50 ii b , 50 ii c and 50 ii d to deflect inwardly to a greater extent than would be the case without the projections ) when it is moved to the second or activated position . in order to ensure that the ring 60 ′ does not move back to the original position ( after being moved to the second position ), the inner circumferential surface of the ring 60 ′ and the projections of the members 50 ii a , 50 ii b , 50 ii c and 50 ii d can be provided with high friction surfaces such as e . g ., a knurl , a high friction coating , etc . although not shown , when the ring 60 ′ is moved to the second or activated position , the inwardly deflecting members 50 ii a , 50 ii b , 50 ii c and 50 ii d will be deflected inwardly ( as was the case in the previous embodiments ) so that they will biased against the proximal end 2 and frictionally engage the threads thereof when the needle tip 50 ii is unthreaded . as was the case in the previous embodiments , once the needle tip assembly shown in fig3 is installed and the re - use prevention system activated , the needle tip cap 30 can be removed by sliding it off axially . then , the needle cap 40 can also be removed axially . once the pen needle device with the installed needle tip assembly of fig3 has been used to perform an injection , the needle tip 50 ii can be removed in the following ways : one could simply grip the needle tip 50 ii in the area of the ring 60 ′ and unthread it from the threaded proximal end 2 . this is risky , of course , because the user can be inadvertently be pricked by the exposed needle n ; one could re - install the needle cap 40 and then grip the needle tip 50 ii in the area of the ring 60 ′ and unthread it from the threaded proximal end 2 ; one could re - install both the needle cap 40 and the needle tip cap 30 , and then grip the needle tip cap 30 in the area just in front of the flange 30 b and thereafter unthread the entire needle tip assembly thereby causing the needle tip 50 ii to become unthreaded from the threaded proximal end 2 ; and one could re - install only the needle tip cap 30 , and then grip the needle tip cap 30 in the area just in front of the flange 30 b and thereafter unthread the needle tip assembly ( without the cap 40 ) thereby causing the needle tip 50 ii to become unthreaded from the threaded proximal end 2 . as was the case in the previous embodiments , all of these ways are contemplated by the invention for this embodiment , with , however , the first way being the least desirable . as was the case in the embodiment shown in fig2 - 28 , once the needle tip 50 ii is removed from the threaded proximal end 2 ( and because the ring 60 ′ has been moved to the activated position ), the plurality of inwardly deflecting members 50 ii a , 50 ii b , 50 ii c and 50 ii d are caused to move inwardly to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 ii back onto the threaded proximal end 2 of the pen needle device 1 . this occurs in substantially the same way as was shown in fig2 which shows how the plurality of inwardly deflecting members have been moved inwardly to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 ii back onto the threaded proximal end 2 of the pen needle device 1 owing to the fact that they effectively reduce the diameter of the distal opening of the needle tip 50 ii . although not shown , the embodiment shown in fig3 can , like the previous embodiments , utilize the needle tip cap shown in fig4 - 49 instead of the needle tip cap 30 shown in fig3 . of course , the needle tip cap 30 can also have any desired configuration provided that it functions for its intended purpose , and can even be dispensed with without leaving the scope of the invention . in the later case , only the needle cap 40 ( or even one of the type shown in fig5 and 54 ) would need to be utilized ( for safety reasons ) and the user could activate the re - use prevention system by gripping the ring 60 ′ and sliding it distally until it assumes the activated position . fig3 shows still another embodiment of a needle tip assembly . the needle tip assembly includes a needle tip cap 30 having various generally cylindrical portions with different diameters , a needle cap 40 , and a needle tip 50 iii of the type shown in fig3 . as the needle tip cap 30 and the needle cap 40 of the instant embodiment are essentially identical to those used in the previous embodiments , they have been accorded the same reference numerals . in this embodiment also , the proximal end 30 a of the needle tip cap 30 is closed while the distal end includes a circumferential flange 30 b . similarly , the proximal end 40 a of the needle cap 40 is closed while the distal end includes a circumferential flange 40 b . the proximal end of the needle tip 50 iii includes a needle n while the distal end includes an opening which is sized to allow the needle tip 50 iii to be mounted to the threaded proximal end 2 of the pen needle device 1 . in order to ensure that the needle tip 50 iii is prevented from being re - installed onto the proximal end 2 , the needle tip 50 iii utilizes a ring 60 ″ which can move axially from an initial position ( similar to the position shown in fig2 ) to a second position ( similar to the position shown in fig2 ) which causes the four inwardly deflecting members 50 iii a , 50 iii b , 50 iii c and 50 iii d to deflect inwards by an amount which is sufficient to prevent the needle tip 50 iii ( after being removed ) from being re - installed onto the proximal end 2 . as can be seen in fig3 , prior to the needle tip assembly being installed onto the threaded proximal end 2 ( not shown in fig3 ), the four inwardly deflecting members 50 iii a , 50 iii b , 50 iii c and 50 iii d are bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 iii to be installed onto the proximal end 2 in the conventional manner , i . e ., by axially sliding it on or by threading it on . in a manner similar to that shown fig2 , the needle tip assembly of fig3 can be installed onto the threaded proximal end 2 without activating the re - use prevention system or mechanism , i . e ., without causing the ring 60 ″ to move axially to the second or activated position . accordingly , in the position shown in fig3 , the one or more inwardly deflecting members 50 iii a , 50 iii b , 50 iii c and 50 iii d are still bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 iii to be installed onto the proximal end 2 . furthermore , while the ring 60 ″ is in the position shown in fig3 , the needle tip assembly can be removed by e . g ., sliding or threading it off of the threaded end 2 . in the same way as was shown in fig2 , after the needle tip assembly shown in fig3 is installed onto the threaded proximal end 2 ( similar to that shown in fig2 ), the needle tip cap 30 can be further moved axially in the distal direction ( as indicated by the arrow in fig2 ) to the point that it activates the re - use prevention system or mechanism , i . e ., it causes the ring 60 ″ to move axially in the distal direction until it assumes the second or activated position . unlike the previous embodiments which provide for a locking position , i . e ., characterized by engagement between the projections of the inwardly deflecting members and the inner circumferential recess of the ring , this embodiment utilizes no projections on the members 50 iii a , 50 iii b , 50 iii c and 50 iii d and does not therefore utilize the recess for receiving the same on the ring 60 ″. furthermore , unlike the embodiment shown in fig3 , the ring 60 ″ of this embodiment utilizes no inner tapered section . instead , the ring 60 ″ merely frictionally engages with the outer surfaces of the members 50 iii a , 50 iii b , 50 iii c and 50 iii d when it is moved to the second or activated position . in order to ensure that the ring 60 ″ does not move back to the original position ( after being moved to the second position ), the inner circumferential surface of the ring 60 ″ and the outer surface of the members 50 iii a , 50 iii b , 50 iii c and 50 iii d can be provided with high friction surfaces such as e . g ., a knurl , a high friction coating , etc . although not shown , when the ring 60 ″ is moved to the second or activated position , the inwardly deflecting members 50 iii a , 50 iii b , 50 iii c and 50 iii d will be deflected inwardly ( as was the case in the previous embodiments ) so that they will biased against the proximal end 2 and frictionally engage the threads thereof when the needle tip 50 iii is unthreaded . as was the case in the previous embodiments , once the needle tip assembly shown in fig3 is installed and the re - use prevention system activated , the needle tip cap 30 can be removed by sliding it off axially . then , the needle cap 40 can also be removed axially . once the pen needle device with the installed needle tip assembly has been used to perform an injection , the needle tip 50 iii can be removed in the following ways : one could simply grip the needle tip 50 iii in the area of the ring 60 ″ and unthread it from the threaded proximal end 2 . this is risky , of course , because the user can be inadvertently be pricked by the exposed needle n ; one could re - install the needle cap 40 and then grip the needle tip 50 iii in the area of the ring 60 ″ and unthread it from the threaded proximal end 2 ; one could re - install both the needle cap 40 and the needle tip cap 30 , and then grip the needle tip cap 30 in the area just in front of the flange 30 b and thereafter unthread the entire needle tip assembly thereby causing the needle tip 50 iii to become unthreaded from the threaded proximal end 2 ; and one could re - install only the needle tip cap 30 , and then grip the needle tip cap 30 in the area just in front of the flange 30 b and thereafter unthread the needle tip assembly ( without the cap 40 ) thereby causing the needle tip 50 iii to become unthreaded from the threaded proximal end 2 . as was the case in the previous embodiments , all of these ways are contemplated by the invention for this embodiment , with , however , the first way being the least desirable . as was the case in the embodiment shown in fig2 - 28 , once the needle tip 50 iii is removed from the threaded proximal end 2 ( and because the ring 60 ″ has been moved to the activated position ), the plurality of inwardly deflecting members 50 iii a , 50 iii b , 50 iii c and 50 iii d are caused to move inwardly to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 iii back onto the threaded proximal end 2 of the pen needle device 1 . this occurs in substantially the same way as was shown in fig2 which shows how the plurality of inwardly deflecting members have been moved inwardly to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 iii back onto the threaded proximal end 2 of the pen needle device 1 owing to the fact that they effectively reduce the diameter of the distal opening of the needle tip 50 iii . although not shown , the embodiment shown in fig3 can , like the previous embodiments , utilize the needle tip cap shown in fig4 - 49 instead of the needle tip cap 30 shown in fig3 . of course , the needle tip cap 30 can also have any desired configuration provided that it functions for its intended purpose , and can even be dispensed with without leaving the scope of the invention . in the later case , only the needle cap 40 ( or even one of the type shown in fig5 and 54 ) would need to be utilized ( for safety reasons ) and the user could activate the re - use prevention system by gripping the ring 60 ″ and sliding it distally until it assumes the activated position . fig3 and 37 show an optional needle tip 50 iv which can be used with any of the embodiments disclosed herein . unlike the previous embodiments which utilize a essentially rigid or semi - rigid ring , this embodiment utilizes an elastic - type ring 60 iii ; that is a ring which functions like an expanded rubber band that wants to contract . indeed , the invention contemplates that the ring 60 iii can be a rubber band ring or even a split spring metal ring which wants to contract but is kept expanded by virtue of being mounted to a portion of the body of the needle tip 50 iv which prevents its contraction . furthermore , unlike the previous embodiments which utilize inwardly deflecting members which are caused to move inwardly by the ring , this embodiment utilizes four equally angularly spaced slots 50 iv a , 50 iv b , 50 iv c and 50 iv d , which weakens the distal end of the needle tip 50 iv to the point that when , the ring 60 iii is moved over the slots 50 iv a , 50 iv b , 50 iv c and 50 iv d , the distal end of the needle tip 50 iv will deflect inwardly to the point that it will not permit ( i . e ., it will interfere with ) re - installation of the needle tip 50 iv back onto the threaded proximal end 2 of the pen needle device 1 owing to the fact that they effectively reduce the diameter of the distal opening of the needle tip 50 iv . the needle tip 50 iv , like the second embodiment , does not utilize any internal threads in the body of the needle tip 50 iv ( i . e ., the distal opening which receives therein the threaded proximal end 2 is generally cylindrical and smooth ). as is evident from fig3 , once the needle tip 50 iv is removed from the threaded proximal end 2 ( and because the ring 60 iii has been moved to the activated position ), the distal end of the needle tip 50 iv deflects inwardly to the point that it will not permit ( i . e ., will interfere with ) re - installation of the needle tip 50 iv back onto the threaded proximal end 2 of the pen needle device 1 . when this occurs , the distal end of the needle tip 50 iv effectively reduces the diameter of the distal opening of the needle tip 50 iv . fig3 and 40 show an optional needle tip 50 v which can be used with any of the needle tip assembly embodiments disclosed herein . the ring 60 can be , by way of non - limiting example , of the type described above in fig3 and 32 . the needle tip 50 v can be , by way of non - limiting example , of the type described above in fig2 and 30 , except that it additionally utilizes a plurality of , e . g ., equally angularly spaced , guide / engaging projections 50 v e which are sized and configured to slide within correspondingly placed guide / engaging recesses 30 ′ g arranged on the needle tip cap 30 ′. this embodiment similarly utilizes four equally angularly spaced members 50 v a , 50 v b , 50 v c and 50 v d , which can be moved inwardly by the ring 60 to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 v back onto the threaded proximal end 2 of the pen needle device 1 owing to the fact that they effectively reduce the diameter of the distal opening of the needle tip 50 v . fig4 shows a needle tip cap 30 ′ which can be used with the needle tip 50 v shown in fig3 . the needle tip cap 30 ′ is similar to the cap shown in fig1 and 19 except that it also utilizes e . g ., equally angularly spaced , guide / engaging recesses 30 ′ g which are sized and configured to slidably receive therein correspondingly placed guide / engaging projections 50 v e arranged on the needle tip 50 v . the needle tip cap 30 ′ has a closed proximal end 30 ′ a , an open distal end having a circumferential flange 30 ′ b , a distal opening 30 ′ c sized to receive therein the ring 60 , a shoulder 30 ′ c which engages with a distal end of the ring 60 so as to cause the ring 60 to move to the locked position , a generally circumferential surface 30 ′ e which is sized to slide over an outer surface of the needle tip 50 v and allow for engagement between guide / engaging projections 50 v e and guide / engaging recesses 30 ′ g . of course , the needle tip cap 30 ′ can have any desired configuration provided that it functions for its intended purpose . fig4 - 44 show still another embodiment of a needle tip assembly . the needle tip assembly includes a needle tip cap 300 having a generally cylindrical configuration , a needle cap 40 , and a needle tip 50 ii of the type shown in fig2 and 30 , and except that the ring 60 iv has a different configuration . in this embodiment , the ring 60 iv is generally cylindrical and has a proximal end 60 iv d which engages the shoulder 300 c of the needle tip cap 300 , a distal end having a tapered inner surface 60 iv c configured to facilitate sliding over the deflecting members 50 ″ a / 50 ″ b / 50 ″ c // 50 ″ d , a circumferential recess 60 iv a sized and configured to receive therein the projections p of the members 50 ″ a / 50 ″ b / 50 ″ c // 50 ″ d , and an inner cylindrical surface 60 iv b which is sized to slide over the needle tip body . of course , the ring 60 iv can have any desired configuration provided that it functions for its intended purpose . additionally , the ring 60 iv has a generally circumferential proximal flange 60 iv d which prevents the needle tip cap 300 from sliding off the ring 60 iv in the proximal direction . the ring 60 iv also has a generally circumferential retaining projection 60 iv f which ensures that the needle tip cap 300 is able to move the ring 60 iv in the distal direction so as to cause it to lock to the needle tip 50 ″. however , after the ring 60 iv becomes locked to the needle tip 50 ″, the projection 60 iv f will not be able to prevent further movement of the cap 300 and is , in fact , configured to allow ( upon exertion of a predetermined force ) the inwardly projecting circumferential projection 300 e to pass over the projection 60 iv f until the annular surface 300 c of the projection 300 e engages the proximal shoulder of the pen needle device 1 . this is shown in fig4 . as the needle cap 40 of the instant embodiment is essentially identical to that used in the previous embodiment , it has been accorded the same reference numeral . in this embodiment , the proximal end 300 a of the needle tip cap 300 is open ( unlike the previous embodiments ) while the distal end is configured to slide over the proximal portion of the device 1 . similarly , the proximal end 40 a of the needle cap 40 is closed while the distal end includes a circumferential flange 40 b . the proximal end of the needle tip 50 ii includes a needle n while the distal end includes an opening which is sized to allow the needle tip 50 ii to be mounted to the threaded proximal end 2 of the pen needle device 1 . in order to ensure that the needle tip 50 ii is prevented from being re - installed onto the proximal end 2 , the needle tip 50 ii utilizes the ring 60 iv which can move axially from an initial position ( shown in fig4 ) to a second or locked position ( shown in fig4 ) which causes the four inwardly deflecting members 50 ii a , 50 ii b , 50 ii c and 50 ii d to deflect inwards by an amount which is sufficient to prevent the needle tip 50 ii ( after being removed ) from being re - installed onto the proximal end 2 . as can be seen in fig4 , prior to activation , the four inwardly deflecting members 50 ii a , 50 ii b , 50 ii c and 50 ii d are bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 ii to be installed onto the proximal end 2 , i . e ., by axially sliding it on or by threading it on . as can be seen in fig4 , the needle tip assembly of fig4 can be installed onto the threaded proximal end 2 without activating the re - use prevention system or mechanism , i . e ., without causing the ring 60 iv to move axially to the second or activated position . accordingly , in the position shown in fig4 , the one or more inwardly deflecting members 50 ii a , 50 ii b , 50 ii c and 50 ii d are still bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 ii to be installed onto the proximal end 2 . furthermore , while the ring 60 iv is in the position shown in fig4 , the needle tip assembly can be removed , e . g ., by sliding it off of the threaded end 2 . as is evident from fig4 , after the needle tip assembly shown in fig4 is installed onto the threaded proximal end 2 , the needle tip cap 300 can be further moved axially in the distal direction ( as indicated by the arrow in fig4 ) to the point that it activates the re - use prevention system or mechanism , i . e ., it causes the ring 60 iv to move axially in the distal direction until it assumes the second or locked or activated position . like many of the previous embodiments , locking occurs because of engagement between the projections of the inwardly deflecting members and the inner circumferential recess of the ring 60 iv . this locking engagement also ensures that the ring 60 iv does not move back to the original position ( after being moved to the second position ) when the cap 300 is moved in the proximal direction to protect inadvertent contact with the needle n ( see fig4 ). as is evident from fig4 , when the ring 60 iv is moved to the second or activated position , the inwardly deflecting members 50 ii a , 50 ii b , 50 ii c and 50 ii d will be deflected inwardly ( as was the case in the previous embodiments ) so that they will biased against the proximal end 2 and frictionally engage the threads thereof when the needle tip 50 ii is unthreaded . once the needle tip assembly shown in fig4 is installed and the re - use prevention system activated ( see fig4 ), the needle tip cap 300 can be , after being in the position allowing it to be used for injection ( see fig4 ), slid in the proximal direction ( see fig4 ), but , unlike the previous embodiments , it is not removed . then , the needle cap 40 can also be removed axially ( in a manner similar to the previous embodiments ). once the pen needle device with the installed needle tip assembly has been used to perform an injection , the needle tip 50 ii can be removed in the following way : one could re - install the needle cap 40 and then grip the needle tip cap 300 and slid it in the proximal direction until it assumes the position shown in fig4 ; or one could simply grip the needle tip cap 300 and slid it in the proximal direction until it assumes the position shown in fig4 without re - installing the needle cap 40 . in either case , the user can then safely remove the entire needle tip assembly by either removing it axially or unthreading it axially . of course , once removed , the needle tip assembly will be prevented from being re - installed because of the configuration of the ring 60 iv and 50 ″. as was the case in the previous embodiments , all of these ways are contemplated by the invention for this embodiment . although not shown , the embodiment shown in fig4 - 44 can , like the previous embodiments , utilize a needle cap of the type shown in fig5 and 54 ). fig4 shows a needle tip assembly according to still another embodiment of the invention . the needle tip assembly is substantially similar to that shown in fig4 - 44 except that it utilizes a coil compression spring s to bias the needle tip cap 300 in a proximal direction , i . e ., towards the original position . fig4 shows still another embodiment of a needle tip 50 iv which can be used in one or more of the herein disclosed embodiments . the needle tip 50 vi can be utilized with a needle tip cap of the types disclosed herein or not with the former being preferred . a needle cap 40 ( not shown ) can also be utilized . the needle tip 50 vi can be substantially similar to the embodiment shown in fig2 and 30 , except that it also includes a circumferential retaining shoulder rs which ensures that the ring 60 v is axially retained on the body of the needle tip 50 vi . the proximal end of the needle tip 50 vi includes a needle n while the distal end includes an opening which is sized to allow the needle tip 50 vi to be mounted to the threaded proximal end 2 of the pen needle device 1 . in order to ensure that the needle tip 50 vi is prevented from being re - installed onto the proximal end 2 , the needle tip 50 vi utilizes a ring 60 v which can move axially from an initial position ( similar to the position shown in fig2 ) to a second or activated position ( shown in fig4 ) which causes the four inwardly deflecting members 50 vi a , 50 vi b , 50 vi c and 50 vi d to deflect inwards by an amount which is sufficient to prevent the needle tip 50 vi ( after being removed ) from being re - installed onto the proximal end 2 . although not shown , prior to the needle tip assembly being installed onto the threaded proximal end 2 , the four inwardly deflecting members 50 vi a , 50 vi b , 50 vi c and 50 vi d are bent outwardly or deflected outwardly by an amount which is sufficient to allow the needle tip 50 vi to be installed onto the proximal end 2 . in the same way as was shown in fig2 , after the needle tip assembly shown in fig4 is installed onto the threaded proximal end 2 , the needle tip cap 30 ( not shown ) can be further moved axially in the distal direction to the point that it activates the re - use prevention system or mechanism , i . e ., it causes the ring 60 v to move axially in the distal direction until it assumes the second or activated position shown in fig4 . unlike the previous embodiments which provide for a locking position , i . e ., characterized by engagement between the projections of the inwardly deflecting members and the inner circumferential recess of the ring , this embodiment utilizes projections on the members 50 vi a , 50 vi b , 50 vi c and 50 vi d and a recess in the ring 60 v for receiving the same , but does not provide for a locking engagement between these members . instead , the inner recess of the ring 60 v merely frictionally engages with the projections of the members 50 vi a , 50 vi b , 50 vi c and 50 vi d when it is moved to the second or activated position . in order to ensure that the ring 60 v does not move back to the original position ( after being moved to the second position ), the inner circumferential surface of the ring 60 v and the outer surface of the members 50 vi a , 50 vi b , 50 vi c and 50 vi d can be provided with high friction surfaces such as e . g ., a knurl , a high friction coating , etc . as shown in fig4 , when the ring 60 v is moved to the second or activated position , the inwardly deflecting members 50 vi a , 50 vi b , 50 vi c and 50 vi d are deflected inwardly ( as was the case in the previous embodiments ) so that they will biased against the proximal end 2 and frictionally engage the threads thereof when the needle tip 50 vi is unthreaded . once the re - use prevention system is activated ( as shown in fig4 ), the needle tip cap 30 ( not shown ) can be removed by sliding it off axially . then , the needle cap 40 ( not shown ) can also be removed axially . once the pen needle device with the installed needle tip assembly has been used to perform an injection , the needle tip 50 vi can be removed in the following ways : one could simply grip the needle tip 50 vi in the area of the ring 60 v and unthread it from the threaded proximal end 2 . this is risky , of course , because the user can be inadvertently be pricked by the exposed needle n ; one could re - install the needle cap 40 and then grip the needle tip 50 vi in the area of the ring 60 v and unthread it from the threaded proximal end 2 ; one could re - install both the needle cap 40 and the needle tip cap 30 , and then grip the needle tip cap 30 in the area just in front of the flange 30 b and thereafter unthread the entire needle tip assembly thereby causing the needle tip 50 vi to become unthreaded from the threaded proximal end 2 ; and one could re - install only the needle tip cap 30 , and then grip the needle tip cap 30 in the area just in front of the flange 30 b and thereafter unthread the needle tip assembly ( without the cap 40 ) thereby causing the needle tip 50 vi to become unthreaded from the threaded proximal end 2 . as was the case in the previous embodiments , all of these ways are contemplated by the invention for this embodiment , with , however , the first way being the least desirable . as was the case in , e . g ., the embodiment shown in fig2 - 28 , once the needle tip 50 vi is removed from the threaded proximal end 2 ( and because the ring 60 v has been moved to the activated position ), the plurality of inwardly deflecting members 50 vi a , 50 vi b , 50 vi c and 50 vi d are caused to move inwardly to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 vi back onto the threaded proximal end 2 of the pen needle device 1 . this occurs in substantially the same way as was shown in fig2 which shows how the plurality of inwardly deflecting members have been moved inwardly to the point that they will not permit ( i . e ., they will interfere with ) re - installation of the needle tip 50 vi back onto the threaded proximal end 2 of the pen needle device 1 owing to the fact that they effectively reduce the diameter of the distal opening of the needle tip 50 vi . although not shown , the embodiment shown in fig4 can , like the previous embodiments , utilize the needle tip cap shown in fig4 - 49 instead of the needle tip cap 30 . of course , the needle tip cap 30 can also have any desired configuration provided that it functions for its intended purpose , and can even be dispensed with without leaving the scope of the invention . in the later case , only the needle cap 40 ( or even one of the type shown in fig5 and 54 ) would need to be utilized ( for safety reasons ) and the user could activate the re - use prevention system by gripping the ring 60 v and sliding it distally until it assumes the activated position . fig4 - 49 show an optional needle tip cap 3000 which can be used in one or more of the embodiments described herein . the needle tip cap 3000 can be similar to that shown in fig1 and 19 except that it utilize a two - piece folding connectable construction instead of the simple one - piece integral construction shown in fig1 and 19 . in order to connect the two parts 3000 a and 3000 b , the cap 3000 utilizes a living hinge lh at one end and a lock system utilizing a lock member lm and a locking projection lp . this type of cap is advantageous because it allows the user to position the cap 3000 from the side instead of from the needle end . as a result , one can install the cap 3000 with a lower risk of being inadvertently punctured by the needle . fig5 - 52 show another non - limiting embodiment of a needle tip assembly which can be installed onto the proximal end of pen needle device 1 . the needle tip assembly is similar to that shown in the prior art fig1 - 7 except that the needle tip 50 vii includes a rear end cap member ec which is mounted to the needle tip body via a living hinge lh ′. the needle tip cap also includes a mechanism which allows the rear cap member ec to temporarily lock thereto . fig5 shows the needle tip assembly of fig5 after the rear end cap ec is unlocked from the needle tip cap and been deflected distally . in this position , the needle tip cap can then be removed in the manner shown in fig4 . fig5 shows the needle tip 50 vii used in the embodiment shown in fig5 and illustrates how the rear cap ec can be deflected via the living hinge lh ′ to a position prior to covering the distal end of the needle tip 50 vii . the end cap ec can also be utilized in one or more of the embodiments disclosed herein . fig5 shows a needle tip assembly according to another embodiment of the invention . the needle tip is similar to that shown in the prior art fig1 - 7 except that the needle tip includes a needle cap member 40 ′ which is mounted to the needle tip body via a living hinge lh ″. the needle cap also includes a mechanism which allows the needle cap member 40 ′ to temporarily lock to the needle tip body . fig5 shows the needle tip assembly of fig5 after the needle cap 40 ′ is unlocked from the needle tip and been deflected distally . in this position , the needle tip can be used to perform an injection . fig5 - 57 show one non - limiting way in which a plurality of needle tip assemblies of either the prior art variety shown in fig2 - 7 or those of the invention described herein can be packaged in a housing h . the housing h performs the function of storing a number of needle tip assemblies and also functions as a tool for installing one needle tip assembly at a time onto the end of a pen needle . the housing h can be a generally cylindrical member with an open front end and a closed rear end . a plurality of spring retaining members rm can be arranged near the front open end . these members rm normally extend inwardly to prevent the needle tip assembly which is to be installed onto a pen needle from moving back into the housing h . once in the position shown in fig5 , the user can grip the housing h and use it to force it onto the pen needle end 1 . of course , the user will first remove the removable sealing material layer ( not shown ) which is typically adhesively arranged on the open end of the needle tip cap , e . g ., 3 . once the housing h is used to install one of the needle tip assemblies , the user can either leave the housing in the position shown in fig5 . then , when the user desires to install a fresh needle tip assembly on the pen needle end 1 , the user can slide the push button pb in the direction of the open end of the housing h until the next needle tip assembly reaches the position shown in fig5 . in this regard , the inwardly bent free ends of retaining members rm ( a total of e . g ., four , can be utilized ) are designed to deflect outwardly in order to allow the next needle tip assembly to pass by . installation can then occur in the same way as was described with regard to fig5 . once , all of the needle tip assemblies , e . g ., five , are utilized , the housing h can be discarded . as is evident from fig5 - 57 , the push - button slides within an elongated slot sl formed in the side wall of the housing h and has an inner portion which is configured to engage and cause to move the needle tip assemblies arranged in series . of course , the housing h can also have other configurations and can house as few as two or more than five assemblies . the pen needle device described above can also utilize one or more features disclosed in the prior art documents expressly incorporated by reference herein . furthermore , one or more of the various parts of the needle tip assembly can preferably be made as one - piece structures by e . g ., injection molding , when doing so reduces costs of manufacture . non - limiting materials for most of the parts include synthetic resins such as those approved for syringes or other medical devices . furthermore , the invention also contemplates that any or all disclosed features of one embodiment may be used on other disclosed embodiments , to the extent such modifications function for their intended purpose . it is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention . while the present invention has been described with reference to an exemplary embodiment , it is understood that the words which have been used herein are words of description and illustration , rather than words of limitation . changes may be made , within the purview of the appended claims , as presently stated and as amended , without departing from the scope and spirit of the present invention in its aspects . although the present invention has been described herein with reference to particular means , materials and embodiments , the present invention is not intended to be limited to the particulars disclosed herein ; rather , the present invention extends to all functionally equivalent structures , methods and uses , such as are within the scope of the appended claims .
a needle tip assembly includes a needle tip , a needle tip cover structured and arranged to facilitate installation of the needle tip onto at least one of a pen needle , a pre - loaded syringe , and an injection device , and at least one of an arrangement for preventing re - installation or re - use of the needle tip , a safety mechanism coupled to the needle tip via a living hinge , and a safety cover non - removably coupled to the needle tip . this abstract is not intended to define the invention disclosed in the specification , nor intended to limit the scope of the invention in any way .