PREFILLED SYRINGE WITH MEANS FOR PREVENTING PLUNGER REMOVAL

Abstract: A finger grip (13) that prevents unintended removal of the plunger (27) from a syringe vial (11) upon retraction of the plunger rod (21).

Description: PREFILLED SYRINGE WITH MEANS FOR PREVENTING PLUNGER REMOVAL BACKGROUND OF THE INVENTION The present invention generally relates to syringes of a type having one end of a vial closed by a plunger. The present invention relates more specifically to prefilled syringes of a type that combines the syringe vial or body, that is closed at one end by a membrane and closed at the other end by a plunger, with a cannula hub or a finger grip at a respective end thereof. Syringes which would benefit from the present invention are known in the prior art as exemplified by U.S. Patent 5,067,947, which is incorporated herein as if fully set forth. SUMMARY OF THE INVENTION The present invention provides a finger grip that prevents unintended removal of the plunger from a syringe vial upon retraction of the plunger rod. The present invention also provides a finger grip that is less likely to be dislodged from the vial. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates the structural components of a prior art syringe that benefits from the present invention. Figure 2 shows a syringe of the type shown in Figure 1 that incorporates the present invention. Figure 3 shows the syringe of Figure 2 with the plunger in the fully withdrawn position. Figure 4 is an exploded view of the encircled area of Figure 3. DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment of the invention will be described with reference to the drawing figures wherein like numerals identify like elements. A syringe combination which will benefit from the present invention is shown, in section, in Figure 1. The syringe 10 includes a glass vial or cartridge body 11 which has a finger grip 13 mounted on one end and a hub 15 for mounting a needle 17 on the other end. Typically, the needle 17 will have a needle shield 19. Alternatively, the hub 15 might include a uer cap and Luer lock connection. The end of the vial 11 having the hub 15 is sealed prior to use. The contents 25 are retained in the vial 11 by a plunger 27 which effectively seals that end of the vial 11. The plunger 27 has female threads 29 for engagement with the male threads 23 of the plunger rod 21. The finger grip 13 is slidably mounted onto the vial 11 by a base 31 which terminates in a ring 32 that limits movement of the finger grip 13 along the vial 11. At the other end of the vial 11, the needle hub means 15, which mounts the needle 17, has a larger skirt 33 which surrounds the vial 11. The vial engaging portion 35 of hub 15 is sized to engage the metal cap 37 which secures the end seal to the vial 11. Syringes of this type are available from Schott Pharmaceutical Packaging, Inc., of Cleona, PA 17042. Since use of the syringe 10 may occasionally require emptying the contents thereof for mixing with other medications or carrier media and then refilling the syringe, there exist a potential for excessive withdrawal of the plunger rod 21 that may result in displacement or removal of the plunger 27. This potentially exists in the current configuration because the ring 32 typically has an interior diameter that is no less than the interior diameter of the vial 11. In the past this has been sufficient for purposes of locating the finger grip, however, it did not prevent unintended withdrawal of the plunger 27. The invention will be appreciated more fully by reference to Figure 4 which is a greatly enlarged sectional view of the encircled area of Figure 3. As can be seen with reference to Figure 4, the ring 40 of finger grip 13 defines an aperture 42 that is approximately equal to the exterior dimension of the plunger rod 21 and less than the interior diameter of the vial 11. Generally speaking, the aperture 42 need only be of diameter to permit the plunger rod 21 to be assembled to the plunger. In the present case, the aperture must be such that the threaded portion 23 of the plunger rod 21 will pass through the aperture 42 and the rod 21 can be rotated to fasten the threads 23 and 29. Such an aperture 42 will be sufficiently large to permit insertion of the plunger 21 into the vial 11 during movement of the plunger 27. Preferably, aperture 42 is dimensioned to clearly extend beyond the interior of vial 11 so as to create the barrier 44 which blocks egress of the plunger 27. Preferably, ring 40 is not in direct contact with the plunger rod 21. In any event, barrier 44 will always extend beyond the interior of vial 11. It is also preferred that the portion of ring 40 that defines the aperture include an inwardly tapered edge 48 that results in a slightly reduced ring dimension adjacent to the plunger 27. This permits the upper edge of the tapered threaded cylinder to flex outwardly and release the threads 23 of rod 21 from their mate with the threads 29. As a result, withdrawal of the plunger rod 21 to its rear most position will encourage outward deflection that will release the plunger rod 21 from the plunger 27 and allow rod 21 to be withdrawn while maintaining the plunger 27 in the vial 11. As can be seen from Figure 4, the threaded portions 23 and 29 have complementary tapers of about five degrees (5°). The plunger rod 21 is mated to the plunger 27 with only sufficient interconnection security for exerting the force required to retract the plunger 27 through vial 11. This force is well below that which required to dislodge the finger grip 13 from the vial 11. The combination of outward deflection and thread tapers allows dislodgment of the plunger rod 21 from plunger 27 but avoiding damage to the overall syringe resulting from plunger extraction or damage to the finger grip-vial interface as a result of excess mating force. A plunger 27 fabricated from a material having a Shore A durometer of 50 has been found to be satisfactory to meet these conditions . Referring again to Figure 2, an additional feature of the present invention is the provision of an extended or extra long plunger rod 21. By providing additional length on the plunger rod so it extends above the finger grip 13, when the plunger 27 is fully inserted, the present invention facilitates better user finger location and increases the user's control over the plunger rod 21 during retraction of the plunger 27.

Claims: What is claimed is: 1. A finger grip for a syringe of a type having an open ended vial of a predetermined interior dimension that has a first end closed by a plunger that is movable through the syringe body toward a second end, the first end being further closed by a finger grip which defines an aperture that is in axial alignment with the plunger and permits a plunger rod to pass through to the plunger, the finger grip characterized by: a defined aperture dimension that is greater than that of the plunger rod and less than that of the plunger. 2. The finger grip of claim 1 wherein: the portion thereof that defines the aperture tapers inwardly from the vial so as to define a larger aperture in the direction of the plunger. 3. The combination of a prefilled syringe of a type having an open ended vial of a predetermined interior dimension that is closed at one end by a movable plunger with an outwardly facing mating portion and a finger grip that defines an aperture that is in axial alignment with the plunger mating portion and of an interior dimension that passes a plunger rod with a complementary mating portion to the plunger's mating portion for engagement therewith, the combination characterized by: the finger grip aperture being of dimension that permits passage of the plunger rod therethrough but prevents passage of the plunger therethrough. 4. The combination of claim 3 wherein in the mate between the plunger and the rod is severed by abutment with the finger grip that defines the aperture and the finger grip remains attached to the vial .

Inventors: PELLOW JOHN W, PELLOW, JOHN, W.
Applicants: PELLOW JOHN W, SCHOTT PHARMACEUTICAL PACKAGIN, PELLOW, JOHN, W., SCHOTT PHARMACEUTICAL PACKAGING, INC.
Application year: 1999
Main classification: A61M5
IPC codes: A61M5