referring to the drawings , the components of a safety needle assembly incorporating the principles of the instant invention can best be seen . the safety needle assembly 10 includes an outer housing 12 including a collar 13 threaded for quick connection to the receptor on a suitably configured syringe barrel . the diaphragm 15 is mounted within the housing 12 to provide a fluid - tight seal against the housing 12 and has an actuator side 16 , facing the syringe barrel 50 , and a needle side 17 from which the needle 11 projects . the needle 11 is received through the diaphragm 15 , passing through a bore 44 in a central needle support 40 and projecting outwardly therefrom in an axial manner with respect to the housing 12 . the safety needle assembly 10 further includes an actuator 20 which includes a sheath head 21 through which the needle 11 passes and is extendible therefrom . the sheath head 21 includes a body portion 22 and a pair of axially extending legs 24 that project toward the syringe barrel 50 from the body portion 22 and engage with the diaphragm 15 , as will be described in greater detail below . the sheath 25 through which the needle 11 passes is attached to the body portion 22 to form an integrally movable assembly 20 that allows the sheath 25 to extend over the needle 11 to cover the tip 11 a of the needle 11 to prevent exposure thereof after the plunger 55 in the syringe barrel 50 has completely expelled the medicine therein through the needle 11 into the patient . the actuator 20 is movable between an exposed position , as seen in fig3 , in which the needle tip 11 a projects outwardly from the sheath member 25 and is in an operable position for being inserted into an object , such as an iv line or a human patient . once actuated , the sheath member 25 is movable into a covered position , best seen in fig4 , in which the needle 11 is completely covered by the sheath member 25 such that the tip 11 a of the needle 11 is prevented from accidentally injuring someone . the collar 13 is formed with threads 14 , which are preferably located on the interior side of the collar 13 to be engagable with corresponding threads on a syringe barrel 50 located on the exterior side thereof to permit the safety needle assembly 20 to be quickly coupled to the syringe barrel 50 to form an operable safety syringe . the collar 13 is sized to mate directly on a 3 ml syringe barrel , as is depicted in fig1 . syringe barrels 50 having a larger diameter than the standard 3 ml syringe barrel 50 are formed with a connection port 52 having the same external diameter as the end of the 3 ml syringe barrel 50 . a sloped transition portion 54 reduces the diameter of the end of the syringe barrel 50 to the 3 ml size of the connection port 52 . the connection between the collar 13 and the connector port 52 on the syringe barrel 50 can be in the form of a luer lock or any other appropriate quick connect apparatus that is known in the art . the safety needle assembly 20 incorporates a locking mechanism 30 that fixes the actuator 20 in the covered position . preferably , the locking mechanism 30 is formed from a cam member 31 formed on the interior side of each of the actuator legs 24 . the cam member 31 includes a ramp portion 32 angled inwardly toward the syringe barrel 50 , as can be seen best in fig1 , 7 and 8 , that terminates in a lock surface 33 oriented generally perpendicularly to the longitudinal centerline 19 of the safety needle assembly 10 . the cam members 31 are engagable with the central needle support 40 , as will be described in greater detail below , such that the ramp portions 32 deflect the cam member 31 outwardly until the lock surface 32 passes by the central needle support 40 , whereupon the cam members 31 retract inwardly positioning the lock surfaces 33 under the central needle support 40 . this positioning of the lock surfaces 33 under the central needle support 40 occurs as the plunger 55 forces the diaphragm 15 into the housing 12 , as will be described in greater detail below . as is best seen in fig5 , the collar 13 is preferably formed with longitudinally extending ribs 39 to facilitate the gripping of the housing 12 of the safety needle assembly 10 . since the housing 12 must be rotated to thread the safety needle assembly 10 onto the barrel connector 52 , the ribs 39 provide a positive gripping surface for engagement by the health care practitioner &# 39 ; s fingers . the ribs 39 are particularly advantageous when trying to remove the safety needle assembly from the syringe barrel as the housing may be tightened to the point of being difficult to grasp . furthermore , if the health care practitioner &# 39 ; s fingers are wet , the gripping of a smooth housing surface is unlikely to provide sufficient torque on the housing 12 to affect whether tightening or loosening . referring to the housing 12 shown in fig9 - 12 , the housing 12 is formed with a central needle support 40 along the longitudinal centerline 29 of the housing 12 . the central needle support 40 receives the needle through a bore 44 passing along the longitudinal centerline 29 through the central needle support 40 for passage into the diaphragm 15 . the central needle support 40 comprises a lower portion 42 supported on a bridge 43 extending across the diameter of the housing 12 and an upper portion 45 . the upper portion 45 projects above the bridge 43 as an extension of the lower portion 42 . the bore 44 extends continuously through the upper and lower portions 42 , 45 of the central needle support 40 . the upper portion 45 of the central needle support 40 defines a tubular mount at the center of an upper chamber 46 of the housing 12 . the diaphragm 15 is mounted for axial movement along the housing on the upper portion 45 which forms a central mount for the diaphragm 15 . as noted above , the needle 11 passes through the bore 44 into the diaphragm 15 to be in flow communication with the syringe barrel 50 . by standardizing the size of the housing 12 , and by standardizing the outer diameter of the upper portion 45 forming the central mount in the upper chamber 46 , the size and shape of the diaphragm 15 can also be standardized to reduce substantially the number of different parts required to make safety needle assemblies 10 with different needle gauges . the bore 44 will be sized to match the gauge of the needle being utilized in the safety needle assembly , but the magnitude of the diameter of the bore 44 has no bearing on the outer diameter of the upper portion 45 and , thus , the size and shape of the diaphragm 15 can be standardized to fit within the upper chamber 46 . while the outer dimensions of the housing 12 will not vary , the diameter of the bore 44 will vary according to the gauge of the needle 11 being utilized in the safety needle assembly 10 . nevertheless , the formation of the housing 12 can be common with all needle gauges until the bore 44 is drilled into the central needle support 40 . furthermore , the utilization of the upper portion 45 of the central needle support 40 provides additional stability for the needle 11 , as the longer support member 40 through which the bore 44 extends reduces the ability of the needle 11 to move laterally within the safety needle assembly 10 . further commonizing the syringe barrel 50 is necessary for the utilization of a common diameter safety needle assembly . as noted above , the outer housing 12 is sized to fit on the smallest commonly used syringe in medical practice , the 3 ml syringe . accordingly , as can be seen in fig1 , the 3 ml syringe barrel 50 is formed simply with a grip portion 58 at the upper end thereof and a threaded outer surface 59 at the lower end of the syringe barrel 50 . otherwise , the barrel 50 is open at the lower end . typically , the syringe barrel 50 will be shipped in a sterilized package with a suitable sized plunger 55 inserted into the barrel 50 . the syringe barrel 50 could be formed with a barrel lock device ( not shown ) that fixes the plunger 55 in the barrel 50 when the plunger 55 reaches the end of the stroke at the bottom of the barrel 50 . one skilled in the art will recognize that the use of a barrel lock ( not shown ) is not needed for proper operation of the safety needle assembly 10 as will be described in greater detail below . as reflected in fig1 - 18 , syringe barrels 50 that have a larger capacity than 3 ml can also be manufactured to accept the mounting of a safety needle assembly 10 . more particularly , the open lower end of the syringe barrel 50 can be formed with a connection port 52 that has the same diameter as the 3 ml barrel 50 . to carry a greater supply of medicine , the general diameter of the barrel 50 is larger than the 3 ml barrel . however , the lower end of the barrel 50 can be formed with a connection port 52 , as is depicted in fig1 - 18 , that will accept the standardized size of the housing 12 . a sloped transition portion 54 reduces the diameter of the barrel 50 from the sized necessary to define the appropriate capacity of the barrel to the common 3 ml size of the connection port 52 . the transition portion 54 is sloped , instead of perpendicular to the centerline 29 of the barrel 50 , so that the medicine within the barrel 50 can be completely dispensed to the patient when the plunger 55 is completely depressed into the syringe barrel 50 . each plunger 55 can be formed to tailor - fit each syringe barrel 50 in terms of diameter of the barrel 50 and in terms of mating with the transition portion 54 so that all of the medicine in the syringe barrel 12 will be dispensed when the plunger 55 is completely depressed . as can be seen in fig1 and 18 , the plunger 55 is shaped to mate with the transition portion 54 of the barrel 50 , and includes an actuation tip 57 that extends into the housing 12 of the safety needle assembly 10 to move the diaphragm 15 as will be described in greater detail below . assembly of the safety needle assembly requires the formation of a standard housing 12 , a standard diaphragm 15 , a needle 11 having a selected gauge , and an actuator 20 , including the body portion 22 with the legs 24 extending axially therefrom and a sheath member 25 affixed to the body portion 22 and extending in the opposite direction from the legs 24 . the actuator 20 is mounted into the housing 12 with the legs 24 extending on opposing sides of the bridge 43 . the tips of the legs 43 are formed in a shape , as is best seen in fig5 - 7 , having a protruding lip 36 that is sized to mate with a matched cavity 19 formed in the diaphragm 15 . thus , the legs 24 are engaged into the cavities 19 in the diaphragm 15 so that the diaphragm 15 is mounted on the actuator 20 . the diaphragm 15 is located in the upper chamber 46 of the housing 12 and mounted on the central mount 45 to be movable axially along the central mount 45 . the needle 11 is passed through the sheath member 25 and the body portion 22 of the sheath head 21 , passing through the appropriately sized bore 44 and through the diaphragm 15 to be in flow communication with the barrel 50 when mounted the safety needle assembly 10 is mounted thereon . in operation , the health care worker would select the barrel 50 having a plunger 55 with a rubber seal 56 positioned within the barrel 50 , with the barrel 50 being open at the distal end where the connector 52 is located with threads 53 thereon being located preferably on the exterior surface thereof . the safety needle assembly 10 is then selected with the needle 11 protected by a safety cap ( not shown ). the collar 13 having the threads 14 ( or outwardly projecting ribs as in a luer lock ) positioned preferably on the interior surface thereof is then engaged with the connector 52 on the barrel 50 and twisted into a locking engagement therebetween . once the safety cap is removed , the assembly safety syringe with detachable safety needle assembly 10 is ready for utilization . as with conventional syringes , the assembled two - piece safety syringe is operated by withdrawing the plunger 55 to affect the intake of liquid medicine into the barrel 50 . once air has been ejected from the barrel 50 , the needle 11 and tubular sheath member 25 are inserted into the selected target . depressing the plunger 55 expels the liquid medicine through the needle 11 and into the selected target until the plunger 55 bottoms out against the diaphragm 15 . at this point , the plunger 55 is not completely inserted into the barrel 50 , as some additional linear movement of the plunger 55 remains available to actuate the locking mechanism 30 . this last movement of the plunger 55 drives the diaphragm 15 axially along the central mount 45 deeper into the upper chamber 46 of the housing 12 . the axial movement of the diaphragm 15 , due to the engagement of the legs 24 in the cavities 19 of the diaphragm 15 , pushes the actuator 20 along the longitudinal center axis 29 of the assembly 10 outwardly to move the tubular sheath member 25 into the covered position over the needle tip 11 a . the locking mechanism 30 engages when the actuator 20 has moved into the covered position , which preferably corresponds to the plunger 55 bottoming out into the barrel 50 . the locking mechanism 30 is engaged due to the axial movement of the actuator 20 in response to the plunger 55 driving the diaphragm 15 deeper into the upper chamber 46 of the housing 12 . the cam members 31 formed on the interior side of the legs 24 move axially with the rest of the actuator 20 , with the sloped ramp portions 32 springing the legs 24 slightly outwardly as the cam members 31 pass the bridge 43 supporting the central needle support 40 within the housing 12 . once the lock surfaces 33 pass below the bridge 43 , the legs 24 spring back into position driving the lock surfaces 33 under the bridge 43 , which will restrict the return of the cam members 31 , and then the actuator 20 back past the bridge 43 . with the needle 11 covered , the needle 11 and tubular sheath member 25 are withdrawn from the selected target . since the locking mechanism 30 prevents the actuator 20 from moving out of the covered position , the point 11 a of the needle 11 will not be exposed to present an opportunity for an accidental stick into the health care practitioner , or to present an opportunity for the safety needle assembly 10 to be re - used , whether remaining engaged with the barrel 50 , or removed from the barrel 50 . the safety needle assembly 10 is intended for use on a syringe barrel 50 configured as shown in fig1 - 18 with a connector port 52 having threads 53 preferably formed on the exterior surface thereof to mate with the threads 14 on the interior surface of the collar 13 of the safety needle assembly 10 . the size or gauge of the safety needle assembly 10 is preferably maintained at a given configuration , such as is conventional for a 3 cc syringe , so that production of the safety needle assembly 10 can be economical . rather than form the safety needle assembly 10 with different sized housings 12 and collars 13 for connection to the correspondingly different sized syringe barrels 50 , having conventional capacities of between 3 cc and 60 cc , the housing 12 and collar 13 are formed at a standard size and the barrels 40 of the syringes are formed to mate with the standardized safety needle assembly 10 . as can be seen in fig1 - 18 , the barrels 40 having a capacity greater than the conventional 3 cc syringe size are formed with a transition portion 54 that reduces the diameter of the barrel 50 from the conventional diameter corresponding to the particular sized syringe being utilized to the connector port 52 diameter corresponding to the standardized safety needle assembly 10 . this transition portion 48 is formed with angularly sloped walls that span between the larger diameter of the large syringe barrel 50 to the standardized connector 52 diameter . the plunger 55 must then be formed with a mating configuration that closes against the sloped sides of the transition portion 54 when the plunger 55 is completely depressed into the barrel 40 so that all of the fluid material within the barrel 40 is expelled from the barrel 50 through the needle 11 . the seal 56 at the end of the plunger 55 will be formed with a tapered tip 57 that will extend into the housing 12 of the attached safety needle assembly 10 to actuate the locking mechanism 30 therein by engaging the diaphragm 15 when the plunger 55 has been fully depressed into the barrel 50 . the tapered shape of the tip 57 allows the last droplets of the fluid material within the barrel 50 to pass out of the barrel 50 and around the tip 57 to reach the diaphragm 15 and be expelled through the needle 11 . alternatively , the tip 57 could be have a constant diameter that is formed with one or more grooves extending axially along the tip 57 to permit the passage of liquid medicine from the barrel 50 as the plunger seal 56 bottoms out at the tapered transition portion 54 . some health care practitioners prefer to draw medicine into the syringe barrel 50 with a large gauge needle so that the barrel 50 fills more rapidly . such large gauge needles are then replaced with a smaller gauge needle that is inserted into the patient to inject the medicine from the syringe barrel 50 . furthermore , some health care practitioners prefer to inject medicines into their patient with a “ fresh ” needle having a point that hasn &# 39 ; t been dulled through previous usage . while this practice is possible with the safety needle assembly 10 described above , utilizing a large gauge safety needle assembly 10 just to draw medicine into the syringe barrel 50 would be cost prohibitive . accordingly , an alternative configuration that would enable the syringe barrels 50 , as described above , to be utilized with a common standard needle 65 having a luer lock 66 mounting apparatus . referring now to fig1 - 22 , an adapter 60 is provided with a mounting collar 61 that is sized and threaded to mount on the connection port 52 of the syringe barrel 50 and an integral connection bell 62 that incorporates luer lock threading 64 on the inside thereof . the connection bell 62 includes a tip 63 that engages into the needle hub 67 to direct the medicine from the barrel 50 into the attached standard needle 65 that is mounted thereon as described below . instead of mounting a safety needle assembly 10 on the connection port 52 of the syringe barrel 50 , the adapter 60 can be mounted , as is depicted in fig2 , so that a common standard needle 65 can be mounted on the adapter 60 , as is reflected in fig2 and 23 . in operation , the health care practitioner can start by selecting a syringe barrel 50 of the size needed to dispense the quantity of medicine needed . an adapter 60 , which could come packages with the standard needle 65 already mounted thereon or as a separate component so that any desired size of common standard needle 65 can be mounted thereon , is mounted on the connection port 52 by screwing the mounting collar 61 thereon . the desired common needle 65 can then be selected , which typically comes packaged with a safety cover ( not shown ) mounted thereon , and mounted into the connection bell 62 by threading the luer lock ribs 66 into the threaded connection bell 62 . typically , this will be a large gauge needle 65 that will rapidly draw the medicine into the syringe barrel 50 . after the medicine is drawn into the syringe barrel 50 , the uninfected needle 65 can be recovered with the safety cover ( not shown ), then the adapter 60 removed from the connection port 52 and properly disposed in a sharps container . the safety needle assembly 10 can then be mounted on the connection port , as described above , air ejected out of the barrel 50 and then inserted hypodermically into the patient to inject the medicine . the safety needle assembly 10 , locked into a covered position by the lock mechanism actuated by the plunger reaching its end movement , can then be safely removed from the syringe barrel 50 and properly disposed in the sharps container . the syringe barrel 50 can be disposed in either the sharps container or in another appropriate manner to make use of recycling and reduce the hazardous waste disposal . the standardized safety needle assembly 10 can be produced in mass production and packaged in a sterile container in a conventional manner . since the only variation in the safety needle assembly 10 will be the gauge of the needle 11 being selected , the number of needle varieties that must be available is significantly reduced , as each available gauge of needle does not have to be manufactured in each barrel diameter . the application of the safety needle assembly 10 to a particular syringe barrel 50 requires the manual grasping of the housing 12 of the safety needle assembly 10 in one hand and a grasping of the syringe barrel 50 in the other hand , following by a turning motion to engage the housing collar 13 with the connection port 52 to attach the housing 12 of the safety needle assembly 10 on the syringe barrel 50 . this connection of the safety needle assembly 10 requires only that the collar 13 on the housing 12 be threaded onto the connector port 52 of the barrel 50 by engaging the respective threads and turning . while the concept of a standardized needle assembly diameter that would fit on a connector port having a diameter corresponding to the attachable needle housing would apply to any form of needle assembly , the concept is particularly advantageous with respect to the utilization of safety needle assemblies 10 because of the manufacturing requirements of providing many different diameters of housings that would otherwise be needed to mate with the differently sized syringe barrels 50 . thus the use of safety needle assemblies is further facilitated while minimizing accidental sticks after prior utilization and discouraging and preventing re - use of the needle . in addition , as is disclosed in aforementioned u . s . pat . no . 6 , 626 , 863 , the plunger 55 can also be provided with an internal locking mechanism between the plunger 55 and the walls of the barrel 50 to prevent the withdrawal of the plunger 55 from the barrel 50 once completely depressed into the barrel 50 . the invention of this application has been described above both generically and with regard to specific embodiments . although the invention has been set forth in what is believed to be the preferred embodiments , a wide variety of alternatives known to those of skill in the art can be selected within the generic disclosure . it will be understood that changes in the details , materials , steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention . the foregoing description illustrates the preferred embodiment of the invention ; however , concepts , as based upon the description , may be employed in other embodiments without departing from the scope of the invention .
a safety needle assembly having a rigid housing that encloses a locking mechanism , an actuator that is operable to slide a sheath over the tip of the needle to prevent accidental sticks after the needle has been used , and an actuator that is operable in response to the final end movement of the syringe plunger to effect movement of the actuator over the needle tip . the housing is made in a standard size that is mountable on a connection port formed on a syringe barrel that can have a much greater diameter than the connection port . an adapter is provided for mounting a standard needle having a luer lock to enable a health care professional the flexibility to use conventional needles to load medicine into the syringe barrel then replacing with a safety needle assembly for injection of the medicine .