referring initially to fig1 , a syringe device for expelling a fluid through a needle mounted on a hub is shown and generally designated 10 . as shown in fig1 , the device 10 includes a substantially cylindrical syringe body 12 that is centered on an axis 14 and formed with a finger grip 16 at its proximal end . fig1 further shows that the device 10 includes an adapter 18 sized to fit within the syringe body 12 . the adapter 18 includes a cylindrical portion that is also centered on the axis 14 . for the device 10 , a substantially cylindrical needle guard 20 is provided and positioned co - axially with both the syringe body 12 and adapter 18 . the guard 20 is sized to fit within the adapter 18 . it can be further seen that the device 10 includes a plunger 22 that is formed with a grip flange 24 at its proximal end . referring to fig2 , a straight , elongated hypodermic needle 26 is shown extending from a sharp needle tip 28 to a needle hub 30 . as best seen in fig3 a , the needle 26 may be mounted to the passively guarded , fillable injection device 10 . specifically , the device 10 includes a luer member 32 that receives and engages the needle hub 30 . the luer member 32 has a proximal portion or head 34 . extending distally from the head 34 is a substantially cylindrical shaft 36 centered on the axis 14 . the needle hub 30 is mounted to the luer member 32 at the shaft &# 39 ; s distal portion or distal shaft end 38 . additionally , the head 34 has a proximal side 33 and a distal side 35 that engages the adapter 18 . circumferentially - spaced truss - like webs 40 are provided on the luer member 32 to reinforce the connection between the shaft 36 and the head 34 . furthermore , the luer member 32 includes a pipe - like conduit 39 that extends from the proximal side 33 of the head 34 to the shaft end 38 . when the needle hub 30 is frictionally mounted on the shaft end 38 , the needle hub 30 and luer member 32 are sealed together to establish fluid communication between the needle 26 and the conduit 39 . as shown in fig3 a , the adapter 18 engages the luer member 32 about the webs 40 thereby preventing rotational movement therebetween . the adapter 18 includes a substantially cylindrical wall 42 that is centered on the axis 14 and forms a cavity 43 . the wall 42 extends from a proximal end 44 substantially covered by a base 45 to an open distal end 46 . at its proximal end 44 , the adapter 18 has a narrow circumference and is designed to engage the distal side 35 of the head 34 of the luer member 32 . at its distal end 46 , the adapter 18 has a broad circumference and is designed to engage the plunger 22 and receive the guard 20 . as can be seen in fig3 a , the adapter 18 also includes two oppositely positioned , axially aligned slits 48 . as best seen in fig3 a , the adapter 18 is sized to allow the cylindrical guard 20 to move along the axis 14 into and out of the adapter cavity 43 . specifically , the guard 20 may be moved between an extended position 49 ( shown in fig3 a and 4a ) to a retracted position 53 ( shown in fig3 b and 4b ). structurally , the guard 20 is a shell forming a lumen 51 that extends between an open proximal end 50 and an open distal end 52 . the guard 20 includes abutments 54 that extend radially outward from the proximal end 50 . also in fig3 a , it can be seen that the inverted plunger 22 has a substantially cylindrical side member 56 that extends from a closed proximal plate member 58 to an open distal edge 60 . structurally , the cylindrical side member 56 surrounds a fluid chamber 62 and is slidingly mounted on the proximal end 44 of the adapter 18 . fig3 a further shows that the plunger 22 is formed with tangs 64 that extend radially inward ( i . e . toward the axis 14 ) and distally from the cylindrical side member 56 of the plunger 22 . it can be seen in fig3 a , that the device 10 includes an elastomeric seal 66 that is attached onto the proximal end 34 of the luer member 32 . specifically , the seal 66 is press fitted onto the proximal end 34 of the luer member 32 . as shown , the seal 66 has a generally fusiform or spindle - like shape and is formed with a through - hole 68 . when the open distal edge 60 of the plunger 22 is slid over the luer member 32 and adapter 18 , the seal 66 compresses between the luer member 32 and the cylindrical side member 56 of the plunger 22 to establish sealed fluid communication between the fluid chamber 62 and the conduit 39 of the luer member 32 . when the needle hub 30 is mounted on the luer member 32 to establish fluid communication between the needle 26 and the conduit 39 , the plunger 22 can be moved to a withdrawn position 61 ( shown in fig3 b and 4b ) to draw fluid through the needle 26 and into the chamber 62 . furthermore , the plunger 22 can be moved to an advanced position 63 ( shown in fig3 c and 4c ) to expel fluid from the chamber 62 through the needle tip 28 . as further shown in fig3 a , the syringe body 12 extends from an open proximal end 70 to an open distal end 71 . positioned at the proximal end 70 , the finger grip 16 includes a recess 72 sized to receive the grip flange 24 of the plunger 22 . functionally , the plunger 22 can be advanced distally after an injection until the grip flange 24 is positioned in the recess 72 . once the grip flange 24 is positioned in the recess 72 it cannot be removed ; therefore , subsequent movement of the plunger 22 relative to the syringe body 12 is effectively prevented . turning to fig4 a , other features of the device 10 may be seen . specifically , the adapter 18 is shown having cam levers 74 positioned at its distal end 46 . the cam levers 74 are in a biased position 76 in which the plunger 22 forces them to be coincident with the rest of the cylindrical wall 42 . however , the cam levers 74 mechanically prefer a relaxed position 78 ( shown in fig4 b ) in which the distal ends 80 of the cam lever 74 extend radially outward from the cylindrical wall 42 . as shown in fig4 a , the guard 20 has hinges 82 . similar to the cam levers 74 of the adapter 18 , the hinges 82 of the guard 20 have a relaxed position 84 in which the proximal ends 86 of the hinges 82 extend radially outward from the rest of the guard 20 . the biased position 88 of the hinges 82 is shown in fig4 b . as further shown in fig4 a , the syringe body 12 can also include flanges 90 at its distal end 71 . the flanges 90 extend distally and radially inward from the cylindrical portion 92 of the syringe body 12 . their purpose is discussed below . by cross - referencing fig3 a - d and 4 a - d , it can be seen that the device 10 includes a mechanism to lock the guard 20 in an extended position 49 covering the needle tip 28 prior to an injection procedure . once locked , the guard 20 can only be unlocked by movement of the plunger 22 . as previously discussed , the adapter 18 is formed with cam levers 74 having distal lever ends 80 . comparing fig4 a with fig4 b , it can be seen that the cam levers 74 are deflectable by the cylindrical side member 56 of the plunger 22 from a relaxed position 78 ( fig4 b ) to a biased position 76 ( fig4 a ). in the relaxed position 78 ( fig4 b ), the cam levers 74 extend radially outward from the remaining cylindrical section of the adapter 18 . on the other hand , as shown in fig3 a , in the biased ( i . e . deflected ) position 76 , the cam levers 74 are coincident with the remaining cylindrical wall 42 of the adapter 18 . when the plunger 22 is in the advanced position 63 shown in fig4 a , the cylindrical side member 56 of the plunger 22 contacts the cam levers 74 and deflects them into the biased position 76 . as shown in fig4 a , when the cam levers 74 are in the biased position 76 , the lever ends 80 engage the proximal ends 86 of the hinges 82 of the guard 20 and prevents proximal movement of the guard 20 . when the plunger 22 is in its withdrawn position 61 as shown in fig3 b and 4b , the cam lever 74 relaxes into its undeflected , outward position 78 ( as shown in fig4 b ) and allows the guard 20 to move proximally . as an additional locking mechanism , the syringe body 12 may be moved relative to the adapter 18 to deflect the cam levers 74 of the adapter 18 with its flanges 90 . as shown in fig4 d , the flanges 90 are moved toward the adapter 18 when the plunger 22 and adapter 18 are fully pushed into the syringe body 12 . as a result , the flanges 90 contact and force the cam levers 74 of the adapter 18 to the biased position 76 to lock the device 10 to prevent any further proximal movement of the needle guard 20 . this prevents inadvertent reuse of the device 10 . initially , the device 10 is provided without a needle 26 . to mount a needle 26 on the device 10 , the needle guard 20 is first moved to the retracted position 53 by withdrawing the plunger 22 . then the needle hub 30 is frictionally engaged with the shaft end 38 of the luer member 32 as can be understood from fig3 b and 4b . after mounting the needle hub 30 on the shaft end 38 , the needle guard 20 is allowed to move to its extended position 49 to cover the needle 26 by moving the plunger 22 to its advanced position 63 as shown in fig3 a . as further shown in fig3 a the tangs 64 of the plunger 22 extend through the slits 48 in the adapter 18 to engage the abutments 54 and retract the guard 20 when the plunger 22 is withdrawn . from fig4 a , it can be seen that the cylindrical side member 56 of the plunger 22 holds the cam levers 74 deflected inward to lock the guard 20 and prevent proximal movement of the guard 20 . as illustrated by fig3 a - b and 4 a - b , use of the device 10 begins by withdrawing the plunger 22 . such proximal movement of the plunger 22 has several effects . specifically , as shown in fig4 a and 4b , initial proximal movement of the plunger 22 allows the cam levers 74 to relax outwardly from the axis 14 and unlock the guard 20 for proximal movement . as shown in fig3 a and 3b , additional proximal movement of the plunger 22 engages the tangs 64 with the abutments 54 , causing the guard 20 to be retracted with the plunger 22 . also , withdrawal of the plunger 22 draws air ( or other fluid ) through the needle 26 and into the fluid chamber 62 . once the guard 20 has been retracted as shown in fig3 b and 48 , the next step is to insert the exposed distal needle tip 28 into a medicament vial ( illustrated by surface 94 in fig3 c and 4c ). at this point , the plunger 22 can be depressed as shown in fig3 c and 4c to expel air into the vial and void the fluid chamber 62 . comparing fig3 b and 4b with fig3 c and 4c , it can be seen that during its advance the plunger 22 disengages the guard 20 . thus , as illustrated by fig3 c and 4c , after advancing the plunger 22 , distal movement of the guard 20 is only prevented by the contact between the distal end 52 of the guard 20 and the surface 94 . next , the plunger 22 can be withdrawn to fill the chamber 62 with medicament fluid 95 ( note fig3 b and 4b are representative of the configuration of the device 10 after the chamber 62 is filled with medicament 95 ). from fig3 b , it can be seen that during withdrawal of the plunger 22 , the tangs 64 reengage the abutments 54 . the result is that the plunger 22 engages the guard 20 and prevents distal advancement of the guard 20 . as illustrated by fig3 b and 4b , when the needle 26 is removed from the vial , the distal tip 28 of the needle 26 remains unguarded and exposed . the device 10 is now ready for an injection . as illustrated by fig3 c and 4c , to inject a medicament into a patient , the distal tip 28 of the needle 26 is inserted into the patient ( represented by surface 94 ) and the plunger 22 is depressed . as shown in fig3 c , the distal advancement of the plunger 22 releases the guard 20 . once released , the guard 20 is free to move distally under the influence of a coil spring 96 that is interposed between the guard 20 and the adapter 18 . thus , as the needle 26 is withdrawn from the patient , the needle 26 retracts proximally into the guard 20 which remains in contact with the patient &# 39 ; s skin ( represented by surface 94 ). fig3 a and 4a are representative of the device 10 after the needle 26 has been withdrawn from the patient and the needle 26 has passively retracted into the guard 20 . once the device 10 has been removed from the patient , the plunger 22 and the adapter 18 can be advanced distally relative to the syringe body 12 to lock the guard 20 in place ( fig4 d ). fig3 d and 4d also show that this places the grip flange 24 of the plunger 22 in the recess 72 formed in the syringe body 12 . functionally , once the device 10 is in the configuration shown in fig3 d and 4d , the plunger 22 is disabled and the guard 20 completely covers the hollow needle 26 to protect the user from unwanted needle sticks and prevents inadvertent reuse of the device 10 . while the particular devices and methods as herein shown and disclosed in detail are fully capable of obtaining the objects and providing the advantages herein before stated , it is to be understood that they are merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims .
a device for expelling a fluid through a needle mounted on a hub includes an elongated luer member that has a distal portion dimensioned to engage the needle hub to provide fluid communication between the luer member and the needle . an adapter anchors the luer member within the device . slidingly mounted on the adapter is a cylindrical - shaped inverted plunger that is movable thereon between an advanced position and a withdrawn position . a needle guard is biased by a biasing member to extend distally from the luer member when the plunger is in the advanced position . the guard is selectively engageable with the plunger to be retracted to expose the distal portion of the luer member for fluid engagement with the needle hub when the plunger is moved to the withdrawn position .