Easy-slip plunger/plunger rod assembly for a syringe or a cartridge

Abstract: A syringe or cartridge (10) , designed for injecting a fluid into a site or withdrawing fluid therefrom, having an improved plunger (50 and 40) the use of which in the syringe or cartridge results in reduced breakaway and running forces between the plunger ring (40) and the barrel (20) of the syringe or cartridge and reduction of contact area between the fluid and the elastomeric plunger ring (40).

Description: Field of the Invention This invention relates to plunger rod and plunger combinations utilized in syringes and cartridges for the introduction or withdrawal of fluids to and from a patient. More particularly, the invention relates to glass or plastic syringes and cartridges which may be pre-filled with a pharmaceutical fluid for injections to a patient. Background of the invention Syringes and cartridges made of glass or polymeric material for delivery of fluids to and from a patient have been proposed and utilized by the prior art, and have achieved a highly developed state. Various requirements related to specific delivery systems have also been addressed. While specific requirements of fluid delivery to and from a patient may vary, means of delivery remain essentially the same and may be characterized by the following general description of a syringe. A syringe comprises: a) a cylindrical barrel having a proximal end designed for receiving a plunger with or without a plunger rod removably attached to the plunger or being integral with the plunger, and a distal end adapted to mount a needle or luer connector thereon; and b) a plunger slideably mounted in the barrel. The plunger is inserted into the barrel at the proximal end of the syringe and thus when fluid is contained in the barrel it may be expelled by pushing the plunger in the barrel towards its distal end; or when the syringe is used to withdraw fluid from a patient, the plunger located at the distal end of the barrel is pulled towards the proximal end of the syringe thereby drawing fluid into the barrel. Since a fluid-tight seal is necessary between the plunger and the inside wall of the barrel, a resilient rubber tip is positioned on the distal end of the plunger, or typically, the plunger is made of resilient rubber-like material. In some of the syringes of the prior art the rubber tip has been replaced with a generally flat, circular disk as part of the plunger. In order to assure air-tight seal between the inside wall of the syringe barrel and the plunger, prior art plungers are manufactured with a larger outside diameter than the inside diameter of the syringe barrels. When the plunger is introduced into the syringe barrel, it is sufficiently compressed to provide adequate pressure between the inside wall of the syringe and the plunger to seal the interface and withstand the challenges of filling, injecting and withdrawing fluids using the syringe without leakage. In addition to a leakage-proof seal, another requirement in the syringe/plunger combination is the chemical stability of both the syringe and the plunger. While syringes being made of glass or thermoplastic materials are sufficiently chemically inert to pharmaceutical and biological fluids contained therein, the plungers made of natural rubber or butyl rubber have some undesirable properties. The rubber contains additional chemical components such as fillers and accelerators introduced during the curing process which tend to exude to the surface of the plunger during the contact between the plunger and the fluid contained in the syringe. Such exudate is undesirable in an injection or when a biological fluid, such as blood, is withdrawn from a patient for testing purposes. The problem is further aggravated when there is a long-term storage of the content of the pharmaceutical /biological fluid in the syringe. Recognizing the problem of contamination caused by exudates from plungers made of rubber, the prior art has provided plungers made of thermoplastic materials which do not contain the additives that rubber plungers contain. However, thermoplastic materials are not as resilient as rubbers and the seals formed between thermoplastic plungers and the inside walls of syringes tend to be inadequate in some circumstances. Also, over a period of time on storage the thermoplastic plunger may achieve a compression stage wherein the outside diameter of the plunger is reduced thereby no longer capable of forming a tight seal between it and the inside wall of the syringe. In addition to the tendency of leakage, the thermoplastic plunger does not slide smoothly in the syringe barrel and requires the exertion of excessive force on the plunger rod to move the plunger in the barrel. The exertion of excessive force on the plunger rod may result in uneven delivery of the fluid to the patient or insertion of the needle into a vein or tissue area to an undesirable depth. In both the rubber and thermoplastic plungers a relatively large compressive force must be exerted on the plungers by the syringe barrel to provide for a tight, leakproof seal. This quality of the seal, however, makes the movement of the plunger difficult. To remedy the problem the prior art used lubricants to reduce friction and drag between the plunger and the inside surface of the syringe barrel. The use of such lubricants, however, is also undesirable with certain parenteral fluids which tend to disperse or dissolve in the parenteral fluids thereby contaminating the parenteral fluids. Attempts to avoid the use of lubricants included the use of various plunger configurations, such as plungers that were provided with one or more ribs projecting forwardly or rearwardly in the barrel to reduce the frictional drag between the plunger and the inside surface of the barrel. As specific documents of the state of the art, some examples are the following: US patent No. 4,543,093 relates to a variable sealing pressure plunger rod assembly comprising a plunger rod and a flexible thermoplastic stopper; the thermoplastic stopper including an inside cavity to receive the distal end portion of the plunger rod; US patent No. 4,673,396 relates to a syringe cartridge used in conjunction with blood gas measurements; the syringe cartridge contains a plunger piston 14 having a dome 62; a pair of seal rings 65 on the exterior of the plunger piston are provided to engage the interior wall of the cartridge; US patent No. 5,314,416 discloses a low friction syringe assembly comprising: a plunger rod and a plunger tip which are designed to provide a low friction resistance against the interior surface of the syringe barrel while the syringe barrel is at rest but which will increase the sealing pressure between the plunger tip and the interior surface of the syringe barrel in proportion to the amount of force applied to the plunger rod; US patent No. 5,413,563 pertains to a pre-filled syringe having a plunger, plunger insert and plunger rod; the plunger insert 68 exerts force against bottom rim 39 of plunger 30 during manual aspiration; US patent No. 5,624,405 relates to a pre-filled syringe and syringe tip assembly comprising: a plunger 6, plunger rod 62 and a gasket 61 fitted on the top of the plunger rod 62 so as to move smoothly along the lumen of the syringe body 1. US 5 453 093 and WO9304951 disclose a dental syringe and a non-reactive composite sealing barrier respectively and disclose the preamble of independant claims 1 and 22 respectively. All of the above-cited references use a plunger rod and a plunger assembly in the barrel of a syringe cartridge or vial and all are, at least in part, directed to a leak-proof seal and easy sliding objective. While fluid tightness and sliding property have improved with these attempts, it appears that improvement in one of these properties is not quite achieved without corresponding decrease in the other property: increasing fluid tightness tends to result in decreasing sliding property, while increasing sliding property tends to result in decreasing fluid tightness. None of the references cited disclose or suggest combination of plunger rod and plunger having the desirable characteristics disclosed in the present invention. The present invention addresses the following main requirements in a syringe or cartridge: reduction of breakaway forces; reduction of running forces; insuring against leakage; and reduction of contact area between the medical fluid and the elastomeric rubber plunger. These and other related requirements will be addressed in the embodiments provided by the present invention the description of which follows. SUMMARY OF THE INVENTION The present invention provides a syringe or a prefilled cartridge for medical use designed for injecting a fluid into a site or, in case of the syringe, also for withdrawing a fluid from a site comprising a syringe or cartridge barrel and a plunger, slideably mounted in said barrel, comprising a rigid plunger rod tip/elastomeric plunger ring assembly. A particular aspect of the invention is a syringe for medical use designed for injecting a fluid into a site or withdrawing a fluid from a site as disclosed in independant claim 1. Another particular aspect of the invention is a prefilled cartridge for medical use designed for injecting a fluid into a site as disclosed in independant claim 22. The non-slideable seal formed between the cylindrical shaft having the groove or recess therein and the elastomeric plunger ring insures against leakage between the two dissimilar materials. The rigid plunger rod tip, preferably made of thermoplastic material does not provide a seal: it freely moves within the barrel of the syringe. However it serves the important function of interfacing with the content of the syringe or cartridge barrel. Since its material of construction is inert to medical fluids there is no contamination of the medical fluids thereby. The plunger rod tip may provide an interface of from at least 95% to about 99% with the medical fluid. The elastomeric plunger ring having plunger ring ribs thereon forms the secondary slideable seal between the plunger rind and the inside of the syringe or cartridge barrel. The contact or interface between the plunger ring ribs and the medical fluid is minimal, thereby contamination from the elastomeric plunger ring ribs by leaching is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the assembled syringe containing a plunger ring, plunger rod and plunger rod tip according to the present invention; FIG. 2 is a longitudinal cross-section of the plunger rod removed from the syringe taken along the line 2-2 of FIG. 1; FIG. 3A is a perspective view of the plunger ring shown in FIG. 1; FIG. 3B is a side elevational view of the plunger ring shown in FIG. 3A; FIG. 4A shows a longitudinal cross-section of the plunger rod tip with plunger ring thereon, wherein the plunger rod tip has internal female threads for attachment to a male-threaded plunger rod; FIG. 4B shows a top plan view of the plunger rod tip with plunger ring thereon shown in FIG. 4A; FIG. 5A shows the longitudinal cross-section of another plunger rod tip designed to carry one internal seal plunger ring thereon wherein the plunger rod tip has internal female threads for attachment to a male-threaded plunger rod; FIG. 5B shows a top plan view of the plunger rod tip shown in FIG. 5A; FIG. 6A shows the longitudinal cross-section of still another plunger rod tip, with accentuated contours, designed to carry one internal seal plunger ring thereon, wherein the plunger rod tip has internal female threads for attachment to a male-threaded plunger rod; FIG. 6B shows a top plan view of the plunger rod tip shown in FIG. 6A; FIG. 7A shows the longitudinal cross-section of still another plunger rod tip designed to carry two internal seals plunger ring thereon, wherein the plunger rod tip has internal female threads for attachment to a male-threaded plunger rod; FIG. 7B shows a top plan view of the plunger rod tip shown in FIG. 7A; FIG. 8 shows the longitudinal cross-section of a plunger ring having one internal seal; FIG. 9 shows the longitudinal cross-section of the plunger ring having one internal seal shown in FIG. 8 and the direction of various pressures exerted on the plunger ring in use; FIG. 10A shows the longitudinal cross-section of still another plunger ring having one internal seal in place on the plunger rod tip; FIG. 10B shows a side elevational view of the cross-section of the plunger ring in place on the plunger rod tip shown in FIG. 10A; FIG. 11A shows the longitudinal cross-section of still another plunger ring having one internal seal in place on the plunger rod tip and is designed to provide leak-proof protection in one direction; FIG. 11B shows a side elevational view of the cross-section of the plunger ring in place on the plunger rod tip shown in FIG. 11A; FIG. 12A shows the longitudinal cross-section of still another plunger ring having one internal seal and is designed to provide leak-proof protection in both directions; FIG. 12B shows a side elevational view of the cross-section of the plunger ring in place on the plunger rod tip shown in FIG. 12A; FIG. 13A shows the longitudinal cross-section of still another plunger ring in place on the plunger rod tip having one internal seal and is designed to provide leak-proof protection in both directions; FIG. 13B shows a side elevational view of the cross-section of the plunger ring in place on the plunger rod tip shown in FIG. 13A; FIG. 14 is a longitudinal fragmentary cross-section of a typical prior art syringe, plunger and plunger rod; FIG. 15 is an enlarged fragmentary cross-section of the prior art plunger and plunge rod of FIG. 14; FIG. 16 shows a graph of breakaway forces between the inside wall of the barrel and a butyl rubber plunger with silicone of the prior art; FIG. 17 shows a graph of breakaway forces between the inside wall of the barrel and the butyl rubber plunger without silicone of the prior art; FIG. 18 shows a graph of running forces between the inside wall of the barrel and the butyl rubber plunger without silicone of the prior art; FIG. 19 shows a graph of running forces between the inside wall of the barrel and the butyl rubber plunger with silicone of the prior art; FIG. 20 shows a graph of average breakaway forces between the inside wall of the barrel and butyl rubber plunger with silicone of the prior art and the average breakaway forces between the inside wall of the barrel and the plunger rod tip/plunger ring combination with silicone of the present invention; FIG. 21 shows a graph of average breakaway forces between the inside wall of the barrel and butyl rubber plunger without silicone of the prior art and the average breakaway forces between the inside wall of the barrel and the plunger rod tip/plunger ring combination without silicone, wherein the plunger ring is made of Silicone(50), Nitrial(65), Nitrial(45), Viton(65) or Butyl(52) rubbers; FIG. 22 shows a graph of running forces between the inside wall of the barrel and the plunger rod tip/plunger ring combination with silicone of the present invention; FIG. 23 shows a graph of running forces between the inside wall of the barrel and the plunger of the prior art made of butyl rubber with silicone, versus a graph of running forces between the inside wall of the barrel and the plunger rod tip/plunger ring combination made of butyl rubber with silicone of the present invention; FIG. 24 shows a graph of running forces between the inside wall of the barrel and the plunger made of butyl rubber without silicone of the prior art; FIG. 25 shows a graph of running forces between the inside wall of the barrel and the plunger rod tip/plunger ring combination without silicone of the present invention; and FIG. 26 shows a graph of running forces between the inside wall of a barrel and the plunger of the prior art made of butyl rubber without silicone, versus a graph of running forces between the inside wall of the barrel and the plunger rod tip/plunger ring combination made of butyl rubber without silicone. DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to syringes and cartridges used to deliver fluids into a site, such as liquid pharmaceutical compositions and diagnostic contrast media delivered into a mammalian patient subcutaneously, intramuscularly or intravenously depending upon the particular medication to be administered. The barrel of the syringe is made of glass or polymeric materials and is equipped with a needle or luer connector having a tubing conduit attached thereto at the distal, tapered end thereof through which the fluids are delivered into the desired site. The syringes or cartridges may be pre-filled and sterilized ready for use, or they may be filled from a container, such as a vial, just prior to use. They may be used manually or in connection with power injectors well-known in the art. The syringes or cartridges of the present invention may also be used to withdraw biological fluids from a patient, such as blood or tissue, for testing or other medical purposes. The design of the thermoplastic plunger rod tip and the elastomeric plunger ring assembly used in the syringe or cartridge results in the following desirable characteristics: reduction of breakaway forces; reduction of running forces; insuring against leakage; and reduction of contact area between the medical fluid and the rubber plunger. The invention will now be described in reference to syringes, however, it is to be noted that the invention encompasses cartridges as well. Reference is now made to the drawings in describing the syringes in general and the thermoplastic plunger rod tip/elastomeric plunger ring assembly in particular detail which together constitute the invention. Referring to FIGS. 1 and 2, there is shown a syringe generally designated 10 comprising: a barrel 20 having inside wall 21, a distal end 22 terminating in a tapered tip 24 which has bore 26 therethrough and proximal end 28 to receive plunger ring 40 to which plunger rod 50 is either removably attached or it may be integral with plunger 40. Plunger rod 50, having distal end 52 and proximal end 60 comprises handle 62 to facilitate exertion of force on plunger ring 40 by plunger rod 50 during operation of the syringe. Disposed about the periphery of proximal end 28 of barrel 20 is finger hub 30 which facilitates holding of barrel 20 during movement of plunger ring 40 by exerting a force on plunger rod 50 in order to move plunger ring 40 in a direction towards the distal end 22 of barrel 20 or in a direction toward the proximal end 28 of barrel 20. Syringe barrel 20 is made of an inert gas impermeable, substantially transparent material, such as polyethylene, polypropylene, polystyrene, acrylic and methacrylic polymers and preferably of glass. Plunger ring 40 is made of compressible, elastomeric materials including: natural rubber; acrylate-butadiene rubber; cis-polybutadiene; chlorobutyl rubber; chlorinated polyethylene elastomers; polyalkylene oxide polymers; ethylene vinyl acetate; fluorosilicone rubbers; hexafluoropropylene-vinylidene fluoride-tetrafluoroethylene terpolymers, such as sold under the tradenames of Fluorel and Viton; butyl rubbers; polyisobutene, such as sold under the tradename Vistanex; synthetic polyisoprene rubber; silicone rubbers; styrene-butadiene rubbers; tetrafluoroethylene propylene copolymers; and thermoplastic-copolyesters. The durometer of the various elastomeric materials should preferably be in the range of from about 25 to about 80 Shore A. Referring to FIG. 1, plunger ring 40 attached to plunger rod 50 is slideably received in barrel 20 by manual force exerted on plunge rod 50. Plunger ring 40 forms a sealing but slideable engagement with inside wall 21 of barrel 20. Referring to FIG. 2, plunger rod 50, having proximal end 60 and distal end 52, further comprises plunger rod tip generally designated at 70. Plunge rod tip 70 having a mushroom shape configuration comprises: a cylindrical shaft 80, the distal end of which is designated at 82 and proximal end is designated at 84, and between the distal end 82 and proximal end 84 of cylindrical shaft 80 there is provided cylindrical recess or groove 86; and cone-shaped head 90 having a circular flange 92, zenith 96 and side 94 connecting flange 92 and zenith 96. Cone-shaped head 90 inside of barrel 20 moves freely without rubbing against inside wall 21 of barrel 20. It is intended to provide a surface area facing the content of the syringe barrel so that, because of its inert thermoplastic composition, no substantial interaction will occur between the content of the barrel and the plunger rod tip 70. Adjacent to proximal end 84 of cylindrical shaft 80, cylindrical shoulder 94 complete the embodiment of plunger rod tip 70. The outside diameter of cylindrical shoulder 94 at least approximates the outside diameter of flange 92 and, preferably is of the same diameter. Plunger rod tip 70 can be integral with plunger rod 50 as shown in FIG. 2 or it can be removably attached to plunger rod 50 at the distal end 52 thereof. When plunger rod tip 70 is intended for use in pre-filled syringes or cartridges, it is not permanently attached, that is, it is not integral with plunger rod 50. In this embodiment plunger rod tip is provided with female internal threads in the center portion thereof so that a male threaded plunger rod could be attached thereto. Cylindrical shaft 80 having distal end 82, proximal end 84 and recess 86 thereon is designed to receive and firmly retain elastomeric plunger ring 40. Referring to FIGS. 3A and 3B, plunger ring 40 is of cylindrical shape and is made of elastomeric materials. It comprises an inside wall 100, and an outside wall 120. Inside wall 100 comprises internal ring 102, slightly protruding out from inside wall 100 toward the center of the ring, designed to engage cylindrical recess or groove 86 on cylindrical shaft 80 thereby to form an internal seal between plunger ring 40 and plunger rod tip 70. Internal ring 102 is firmly held by recess or groove 86 so that upon movement of the plunger rod tip 40 in the barrel 20 of the syringe no disengagement can occur between plunger ring 40 and plunger rod tip 70. In all the embodiments of the present invention there must be at least one internal seal formed between said plunger ring and said plunger rod tip 70. However, more than one such seal may be provided in some of the embodiments depending on the intended use of the syringe. Outside wall 120 of plunger ring 40 comprises at least one, but preferably more, plunger ring rib 122 designed to form secondary seal between it and the inside wall 21 of barrel 20. The configuration of rib or ribs 122 may be horizontal to a plane, or oriented towards the distal or proximal ends of the plunger rod tip 70. Referring to FIGS. 4A and 4B, there is shown in longitudinal cross-section and top plan view a plunger rod tip 130 with plunger ring 140 thereon, wherein the plunger rod tip 130 has internal female threads 134 therein for attachment to a male-threaded plunger rod. Plunger ring 140 comprises: internal ring 142 forming an internal seal between it and recess or groove 136 in plunger rod tip 130; and plunger ring ribs 144 and 146 forming secondary seals with the inside wall of a barrel. As shown, two secondary seals are provided by the presence of the horizontal ribs insuring against leakage when the plunger rod tip is moved in the barrel in the proximal or distal direction. FIGS. 5A and 5B show the longitudinal cross-section and top plan view of a plunger rod tip 150 designed to carry one internal seal plunger ring thereon in recess or groove 152 wherein the plunger rod tip 150 has internal female threads 154 therein for attachment to a male-threaded plunger rod. FIGS. 6A and 6B show another longitudinal cross section and top plan view of a plunger rod tip 160 designed to carry one internal seal plunger ring thereon in recess or groove 162 wherein the plunger rod tip 160 has internal female threads 164 thereon for attachment to a male-threaded plunger rod. The plunger rod tip 160 further comprises accentuated contours at 166, 168, 170, 166', 168' and 170' for insuring retention of a matching plunger ring on said plunger rod tip 160. FIGS. 7a and 7B show another longitudinal cross section and top plan view of a plunger rod tip 180 designed to carry two internal seals plunger ring thereon in recess or groove 184 and 186, wherein the plunger rod tip 180 has internal female threads therein for attachment to a male-threaded plunger rod. The presence of two internal seals further insures against leakage at the interface between the plunger rod tip and the plunger ring. FIG. 8 shows a longitudinal cross-section of a plunger ring 190 having one internal seal provision at 192 with a matching plunger rod tip such as shown in FIGS. 6A and 6B. FIG. 9 shows the longitudinal cross-section of the plunger ring 190 having one internal seal shown in FIG. 8 and the directions of pressures exerted on the plunger ring in use. The plunger ring has minimal contact areas with the inside wall of the barrel. The various designs described in the embodiments of the present invention use a hydraulic action to increase the contact area as the pressure increases during use. In FIG. 9, as illustrated, as pressure increases: area A is forced toward the side of the barrel D; area C is forced towards the plunger tip; and area B is compressed. The same hydraulic action works in both directions, i.e. when the plunger rod tip is forced to travel in the distal or proximal directions. FIGS. 10A and 10B show the longitudinal cross-section and side elevational view of still another plunger ring 200 having one internal seal 202 in place on the plunger rod tip 204 wherein the plunger ring comprises plunger ring rims 206 and 208. FIGS. 11A and 11B show the longitudinal cross section of still another plunger rod tip 210/plunger ring 211 combination having one internal seal 212 in place on the plunger rod tip, wherein the plunger ring comprises plunger ring rims 214, 216 and 218. These rims are designed to provide leak-proof protection in one direction. As shown in the drawings leak-proof protection is achieved when the plunger ring/plunger tip combination is forced to travel distally, such as when the syringe is used for injection. If the syringe is intended for use in withdrawing biological fluid from a patient, the orientation of the plunger ring rib/plunger rod tip combination would be reversed 180°. FIGS. 12A and 12B show a longitudinal cross-section and side elevational view of still another plunger rod tip 220/plunger ring 221 combination having an internal seal 222 in place on the plunger rod tip, wherein the plunger ring comprises plunger ring rims 224, 226 and 228. This embodiment of the present invention is designed to provide leak-proof protection in both the proximal and distal directions. FIGS. 13A and 13B show a longitudinal cross-section and side elevational view of still another plunger rod tip 230 having an internal seal 232 in place on the plunger rod tip/plunger ring 231 combination, wherein the plunger ring comprises plunger ring rims 234, 236 and 238 and 240. This embodiment of the present invention is also designed to provide leak-proof protection in both the proximal and distal directions. FIGS. 14 shows a longitudinal fragmentary cross-section of a typical prior art syringe, plunger and plunger rod; and FIG. 15 show an enlarged fragmentary cross-section thereof. Plunger 250, made of elastomeric material, comprises external plunger rims 252, 254 and 256 which are designed to provide a leak-proof seal between the plunger and the inside wall 260 of barrel 258. Plunger 250 is provided with female threads 262, 264, 266 and 268 to receive a male-threaded plunger rod. Plunger rod 270 of this prior art embodiment comprises shank 272 and plunger rod head 274 which is provided with male threads 276, 278, 280 and 282 to engage female threads 262, 264, 266 and 268. It is apparent that the content of the barrel, such as a medical solution, interfaces with the elastomeric plunger thereby allowing undesirable interaction therebetween. Such interaction may result in the dissolution of at least small amounts of chemicals present in the elastomeric material which then taints the medical fluids. An embodiment of the present invention shown in FIG. 1 was comparatively tested against a corresponding prior art device illustrated in cross-section in FIGS. 14 and 15. The summary of the test results expressed as averages in N (lbs) is shown in Table I. Present Invention Prior Art Breakaway Force With Silicone 0.67 N (0.15 lbs) 19.13 N (4.3 lbs) Breakaway Force Without Silicone 2.71 N (0.61 lbs) 75.17 N (16.9 lbs) Running Force With Silicone 0.76 N (0.17 lbs) 11.12 N (2.5 lbs) Running Force Without Silicone 2.69 N (0.60 lbs) 51.60 N (11.6 lbs) Leakage None Some observed between plunger ribs Test to Failer (Breakage) 400.3 N (90.0 lbs) 382.6 N (86.0 lbs) In addition to the extremely low breakaway and running forces shown in Table I, contact between the medical fluid in the syringe barrel and the elastomeric (rubber) material constituting a portion of the plunger of the present invention was reduced about 80%, thereby reducing the tendency of the presence of elastomeric exudate in the medical fluid. Description of the details of the comparative testing follows. Testing was conducted using three pre-filled syringes for each test. Measurements were made with a standard Test Gauge at five points in the barrel of the syringes as the plunger was forced to travel down towards the distal end of the syringe: Test Point 1 was at the proximal end of the barrel; Test Point 2 was at about 25% down from the proximal end of the barrel; Test Point 3 was at about 50% down from the proximal end of the barrel; Test Point 4 was at about 75% down from the proximal end of the barrel; and Test point 5 was at the distal end of the barrel, close to where the barrel tapers to form the tip. The result of the testing of the syringes are shown in the following Figures. FIG. 16 shows a graph of breakaway forces between the inside walls of three barrels and butyl rubber plungers with silicone of the prior art, wherein Barrel 1, Barrel 2 and Barrel 3 show a breakaway force of 18.68, 19.13 and 19.57 N (4.2, 4.3 and 4.4 pounds), respectively. FIG. 17 shows a graph of breakaway forces between the inside walls of three barrels and butyl rubber plungers without silicone of the prior art, wherein Barrel 1, Barrel 2 and Barrel 3 show a breakaway force of 63.16, 46.26 and 115.65 N (14.2, 10.4 and 26 pounds), respectively. It is apparent that without the use of silicone the breakaway forces have substantially increased. FIG. 18 shows a graph of running forces between the inside walls of three barrels and butyl rubber plungers with silicone of the prior art, wherein the running forces are shown to vary from about 3.34 N to about 23.1 N (about 0.75 pounds to about 5.2 pounds). FIG. 19 shows a graph of running forces between the inside walls of three barrels and butyl rubber plungers without silicone of the prior art, wherein the running forces are shown to vary from about 53.38 N to about 106.76 N (about 12 pounds to about 24 pounds). Again, it is apparent that V without the use of silicone the running forces have substantially increased, similarly to the breakaway forces shown in FIGS. 16 and 17. FIG. 20 shows a graph of average breakaway forces between the inside walls of the barrels and the butyl rubber plungers with silicone of the prior art, and the average breakaway forces between the inside walls of the barrels and the plunger rod tip/plunger ring combination with silicone of the present invention. It is apparent from the graphs that the average breakaway force of the prior art device is many-fold larger than that of the present invention. FIG. 21 shows a graph of average breakaway forces between the inside walls of the barrels and the butyl rubber plungers without silicone of the prior art, and the average breakaway forces between the inside walls of the barrels and the plunger rod tip/plunger ring combination without silicone of the present invention wherein the plunger ring is made of Silicone(50), Nitrial(65), Nitrial(45), Viton(65) or Butyl(52) rubbers the average breakaway force for each of which is shown in the graph. The breakaway forces of the prior art device is at least 25, 14, 140, 120 and 27 times larger than the breakaway forces of the present invention respectively, using the rubber materials from which the plunger rings are made. FIG. 22 shows a graph of running forces between the inside wall of the barrel and the plunger rod tip/butyl rubber plunger ring combination with silicone of the present invention showing the result for each of three barrels. The running forces for Barrel 1 range of from about 0.44 N to about 0.80 N (about 0.1 lbs to about 0.18 lbs), the running forces for Barrel 2 range of from about 0.58 N to about 0.93 N (about 0.13 lbs to about 0.21 lbs), and the running forces for Barrel 3 range of from about 0.58 N to about 1.02 N (about 0.13 lbs to about 0.23 lbs). FIG. 23 shows a graph of running forces between the inside wall of the barrel and the plunger rod of the prior art made of butyl rubber with silicone, versus a graph a running forces between the inside wall of the barrel and the plunger rod tip/plunger ring combination made of butyl rubber with silicone of the present invention. As shown, the running forces of the prior art device are in the range of from about 2.69 N to about 23.13 N (about 0.60 lbs to about 5.2 lbs), while the running forces of the present invention is in the range of about 1.11 N (about 0.25 lbs). FIG. 24 shows a graph of running forces between the inside wall of the barrel and the plunger made of butyl rubber without silicone of the prior art for Barrels 1, 2 and 3. For Barrel 1, the running forces range from about 24.47 N to about 26.69 N (about 5.5 lbs to about 6.0 lbs), for Barrel 2, the running forces range from about 31.14 N to about 53.38 N (about 7.0 lbs to about 12.0 lbs), and for Barrel 3 the running forces range from about 106.76 N to about 80.07 N (about 24.0 lbs to about 18.0 lbs). FIG. 25 shows a graph of running forces between the inside wall of the barrel and the plunger rod tip/plunger ring combination without silicone of the present invention for Barrels 1, 2 and 3. For Barrel 1, the running forces range from about 2.22 N to about 6.23 N (about 0.50 lbs to about 1.40 lbs), for Barrel 2, the running forces range from about 1.78 N to about 2.89 N (about 0.40 lbs to about 0.65 lbs), and the running forces for Barrel 3 range from about 3.56 N to about 2.00 N (about 0.80 lbs to about 0.45 lbs). FIG. 26 shows a graph of running forces between the inside wall of the barrel and the plunger made of butyl rubber without silicone of the prior art for Barrels 1, 2 and 3, versus a graph of running forces between the inside wall of the barrel and the plunger rod tip/plunger ring combination made of butyl rubber without silicone of the present invention. It is apparent from the graphs that the running forces existing in the prior art without the use of silicone are large, while the running forces existing in the present invention without silicone are very low. For the prior art the running forces for Barrel 1 range of from about 24.47 N to about 26.69 N (about 5.5 lbs to about 6.0 lbs), for Barrel 2 the running forces range of from about 40.03 N to about 51.15 N (about 9.0 lbs to about 11.5 lbs), and for Barrel 3 the running forces range of from about 104.53 N to about 80.07 N (about 23.5 lbs to about 18.0 lbs). LIST OF REFERENCE NUMBERS USED Syringe (generally designated) 10 Barrel 20 Inside wall of barrel 21 Distal end of barrel 22 Tapered tip of barrel at distal end 24 Bore through tip of barrel 26 Proximal end of barrel 28 Finger hub on proximal end of barrel 30 Plunger ring (generally designated) 40 Plunger rod (generally designated) 50 Distal end of plunger rod 52 Proximal end of plunger rod 60 Handle of plunger rod 62 Plunger rod tip (generally designated) 70 Cylindrical shaft of plunger rod tip (generally designated) 80 Distal end of plunger rod tip 82 Proximal end of plunger rod tip 84 Cylindrical recess or groove in plunger rod tip 86 Cone-shaped head of plunger rod tip (generally designated) 90 Flange of cone-shaped head of plunger rod tip 92 Cylindrical shoulder on plunger rod tip 94 Inside wall of plunger ring 100 Outside wall of plunger ring 120 Internal ring on inside wall of plunger ring 102 Plunger rod tip (of another embodiment, generally designated) 130 Internal female threads on plunger rod tip 134 Plunger ring (generally designated) 140 Internal ring on inside wall of plunger ring 142 Plunger ring ribs 144,146 Plunger rod tip (of still another embodiment, generally designated) 150 Recess or groove in plunger rod tip 152 Internal female threads on plunger rod tip 154 Plunger rod tip (of still another embodiment, generally designated) 160 Recess groove in plunger rod tip 162 Internal female threads on plunger rod tip 164 Accentuated contours on plunger rod tip 166,168,170,166', 168',170' Plunger rod tip (of still another embodiment, generally designated) 180 Recess or groove in plunger rod tip 184,186 Plunger ring (of still another embodiment, generally designated) 190 Internal seal on plunger ring 192 Plunger ring (of still another embodiment, generally designated) 200 Internal seal on plunger ring 202 Plunger rod tip 204 Plunger ring ribs 206,208 Plunger rod tip (of still another embodiment, generally designated) 210 Plunger ring (generally designated) 211 Internal seal on plunger rod tip 212 Plunger ring ribs 214, 216, 218 Plunger rod tip (of still another embodiment, generally designated) 220 Plunger ring 221 Internal seal on plunger rod tip 222 Plunger ring ribs 224, 226, 228 Plunger rod tip (of still another embodiment, generally designated) 230 Plunger ring 231 Internal seal on plunger rod tip 232 Plunger ring ribs 234, 236, 238, 240 Prior Art Plunger 250 External plunger rims 252, 254, 256 Inside wall of barrel 258 Female threads on plunger 262, 264, 266, 268 Plunger rod 270 Shenk of plunger rod 272 Head of plunger rod 274 Male threads in plunger rod head 276, 278, 280, 282 Various modifications of the present invention disclosed will become apparent. This invention is intended to include such modifications to be limited only by the scope of the claims.

Claims: A syringe (10), optionally prefilled, designed for injecting a fluid into a site or withdrawing a fluid from a site comprising: (a) a syringe barrel (20) having an inner surface (21) defining a cylindrical chamber for retaining a fluid therein; (b) a plunger slideably mounted in said barrel (20) and positioned close to the proximal end (28) of the barrel for injecting a fluid into a site, or positioned close to the distal end (22) of the barrel for withdrawing fluid from a site, characterised in that , said plunger comprises a rigid plunger rod tip (70, 130, 150, 160, 180, 204, 210, 220, 230) and an elastomeric plunger ring (40, 140, 190, 200, 211, 221, 231), wherein said elastomeric plunger ring (40, 140, 190, 200, 211, 221, 231) has an inside wall (100) and an outside wall (120), (1) said inside wall (100) comprises at least one internal ring (102) slightly protruding out towards the centre of the ring designed to engage a recess or groove (86, 152, 162, 184, 186) in a cylindrical shaft (80) of said rigid plunger rod tip (70, 130, 150, 160, 180, 204, 210, 220, 230) and form a non-slideable internal seal therewith; (2) said outside wall (120) comprises at least one plunger ring rib (144, 146, 206, 208, 214, 216, 218, 224, 226, 228, 234, 236, 238, 240) designed to form a secondary slideable seal with the inside wall (21) of said barrel (20). A syringe (10) according to claim 1, wherein said rigid plunger rod tip (70, 130, 150, 160, 180, 204, 210, 220, 230) has a mushroom-shape configuration comprising: (i) the cylindrical shaft (80) having a distal end (82) and a proximal end (84), and the recess or groove (86, 152, 162, 184, 186), between said distal end (82) and said proximal end (84), designed to receive said elastomeric plunger ring (40, 140, 190, 200, 211, 221, 231) and forming non-slideable internal seal therewith; (ii) a cone-shaped head (90) integral with said cylindrical shaft (80), said cone-shaped head (90) having an outside diameter slightly smaller than the inside diameter of said barrel (20) allowing free movement of said cone-shaped head (90) in said barrel (20); (iii) said elastomeric plunger ring (40, 140, 190, 200, 211, 221, 231) mounted on said cylindrical shaft (80) of said rigid plunger rod tip (70, 130, 150, 160, 180, 204, 210, 220, 230). A syringe (10) according to claim 2, wherein said cone-shaped head (ii) (90) has a circular flange (92) on the proximal end thereof, a zenith (96) at the centre on the distal end thereof and side connecting said flange (92) and said zenith (96). A syringe (10) according to claims 1-3, wherein said plunger rod tip (70, 130, 150, 160, 180, 204, 210, 220, 230) is made of polymeric material; said syringe barrel (20) is made of glass or polymeric material, said barrel (20) having: (I) a distal end terminating in a tapered tip (24) and having a bore (26) thereto to which an injection needle or a connector equipped with tubing conduit can be attached; and (II) a proximal end (28) for receiving a plunger. A syringe (10) according to claims 1-4, wherein said rigid plunger rod tip (70, 130, 150, 160, 180, 204, 210, 220, 230) further comprises an integral plunger rod (50) at its proximal end thereof. A syringe (10) according to claims 1-5, wherein said plunger rod tip further comprises attachment means at the proximal end thereof. A syringe according to claim 6, wherein said attachment means comprises female threads (164) in said plunger rod tip (70, 130, 150, 160, 180, 204, 210, 220, 230). A syringe (10) according to claims 1-7, wherein said plunger rod tip (70, 130, 150, 160, 180, 204, 210, 220, 230) comprises two or more recess or grooves (86, 152, 162, 184, 186) to receive said elastomeric plunger ring to form non-slidably seals thereon. A syringe (10) according to claim 8, wherein said elastomeric plunger ring comprises two or more plunger ring ribs (144, 146, 206, 208, 214, 216, 218, 224, 226, 228, 234, 236, 238, 240) thereon to form secondary slideable seals with the inside wall of said barrel. A syringe (10) according to claims 1-9, wherein said plunger ring rib is horizontally oriented towards the inside wall of said barrel. A syringe according to claims 1-9, wherein said plunger ring rib is oriented towards the distal end of the barrel (22). A syringe according to claims 1-9, wherein said plunger ring rib is oriented towards the proximal end of the barrel (28). A syringe according to claims 1-9, wherein at least one of said plunger ring ribs is oriented towards the distal end (22) of the barrel and at least one of said plunger ring ribs is oriented towards the proximal end (28) of the barrel. A syringe according to claims 1-9, comprising three plunger ring ribs one of which is oriented horizontally, the second of which is oriented towards the distal end of the barrel and the third of which is oriented towards the proximal end of the barrel. A syringe according to claims 1-14, wherein said syringe barrel is made of an inert gas impermeable material selected from the group consisting of polyethylene, polypropylene, polystyrenes, acrylic polymers and methacrylic polymers. A syringe according to claims 1-15, wherein said plunger rod tip is made of a thermoplastic material. A syringe according to claims 1-16, wherein said plunger rod tip is made of a material selected from the group consisting of polyethylene, polypropylene, polystyrenes, acrylic polymers and methacrylic polymers. A syringe according to claims 1-17, wherein said plunger ring is made of a compressible, elastomeric material selected from the group consisting of natural and synthetic rubbers. A syringe according to claims 1-18, wherein said elastomeric material is selected from the group consisting of: natural rubber; acrylate-butadiene rubber; cis-polybutadiene; chlorobutyl rubber; chlorinated polyethylene elastomers; polyalkylene oxide polymers; ethylene vinyl acetate; fluorosilicone rubbers; hexafluoropropylene-vinylidene; tetrafluoroethylene terpolymers; butyl rubbers; polyisobutene; synthetic polyisoprene rubber; silicone rubbers; styrene-butadiene rubbers; tetrafluoroethylene propylene copolymers; and thermoplastic-copolyesters. A syringe according to claims 1-19, wherein said fluid is a medical fluid. A syringe according to claim 20, wherein said medical fluid is diagnostic contrast media. A cartridge (10), optionally prefilled, designed for injecting a fluid into a site or withdrawing a fluid from a site comprising: (a) a cartridge barrel (20) of having an inner surface (21) defining a cylindrical chamber for retaining a fluid therein; (b) a plunger slideably mounted in said barrel (20) and positioned close to the proximal end (28) of the barrel for injecting a fluid into a site, characterised in that , said plunger comprises a rigid plunger rod tip (70, 130, 150, 160, 180, 204, 210, 220, 230) and an elastomeric plunger ring (40, 140, 190, 200, 211, 221, 231), wherein said elastomeric plunger ring (40, 140, 190, 200, 211, 211, 231) has an inside wall (100) and an outside wall (120), (1) said inside wall (100) comprises at least one internal ring (102) slightly protruding out towards the centre of the ring designed to engage a recess or groove (86, 152, 162, 184, 186), in a cylindrical shaft (80) of said rigid plunger rod tip and form a non-slideable internal seal therewith; (2) said outside wall (120) comprises at least one plunger ring rib (144, 146, 206, 208, 214, 216, 218, 224, 226, 228, 236, 238, 240) designed to form a secondary slideable seal with the inside wall (21) of said barrel (20). . A cartridge (10) according to claim 22, wherein said rigid plunger rod tip (70, 130, 150, 160, 180, 204, 210, 220, 230) has a mushroom-shape configuration comprising: (i) the cylindrical shaft (80) having a distal end (82) and a proximal end (84), and the recess or groove (86, 152, 162, 184, 186), between said distal end and said proximal end, designed to receive said elastomeric plunger ring (40, 140, 190, 200, 211, 221, 231) and forming the non-slideable internal seal therewith; (ii) a cone-shaped head (90) integral with said cylindrical shaft (80), said cone-shaped head having an outside diameter slightly smaller than the inside diameter of said barrel (20) allowing free movement of said cone-shaped head (90) in said barrel (20); (iii) said elastomeric plunger ring (40, 140, 190, 200, 211, 221, 231) mounted on said cylindrical shaft (80) of said rigid plunger rod tip. A cartridge (10) according to claim 23, wherein said cone-shaped head (ii)(90) has a circular flange (92) on the proximal end thereof, a zenith (96) at the centre on the distal end thereof and side connecting said flange (92) and said zenith (96). A cartridge (10) according to claims 22-24, wherein said plunger rod tip (70, 130, 150, 160, 180, 204, 210, 220, 230) is made of polymeric material; said barrel (20) is made of glass or polymeric material, said barrel having: (I) a distal end terminating in a tapered tip (24) and having a bore (26) thereto to which an injection needle or a connector equipped with tubing conduit can be attached; and (II) a proximal end (28) for receiving a plunger. A cartridge (10) according to claims 22-25, wherein said rigid plunger rod tip further comprises an integral plunger rod (50) at its proximal end thereof. A cartridge according to claims 22-26, wherein said plunger rod tip further comprises attachment means at the proximal end thereof. A cartridge according to claim 27, wherein said attachment means comprises female threads (164) in said plunger rod tip. A cartridge according to claims 22-28, wherein said plunger rod tip comprises two or more recess or grooves to receive said elastomeric plunger ring to form non-slidably seals thereon. A cartridge according to claim 29, wherein said elastomeric plunger ring comprises two or more plunger ring ribs thereon to form secondary slideable seals with the inside wall of said barrel. A cartridge according to claims 22-30, wherein said plunger ring rib is horizontally oriented towards the inside wall of said barrel. A cartridge according to claims 22-30, wherein said plunger ring rib is oriented towards the distal end of the barrel. A cartridge according to claims 22-30, wherein at least one of said plunger ring ribs is oriented towards the distal end of the barrel and at least one of said plunger ring ribs is oriented towards the proximal end of the barrel. A cartridge according to claims 22-30, comprising three plunger ring ribs one of which is oriented horizontally, the second of which is oriented toward the distal end of the barrel and the third of which is oriented towards the proximal end of the barrel. A cartridge according to claims 22-34, wherein said cartridge barrel is made of an inert gas impermeable material selected from the group consisting of polyethylene, polypropylene, polystyrenes, acrylic polymers and methacrylic polymers. A cartridge according to claims 22-35, wherein said plunger rod tip is made of a thermoplastic material. A cartridge according to claims 22-36, wherein said plunger rod tip is made of a material selected from the group consisting of polyethylene, polypropylene, polystyrenes, acrylic polymers and methacrylic polymers. A cartridge according to claims 22-37, wherein said plunger ring is made of a compressible, elastomeric material selected from the group consisting of natural and synthetic rubbers. A cartridge according to claims 22-38, wherein said elastomeric material is selected from the group consisting of: natural rubber; acrylate-butadiene rubber; cis-polybutadiene; chlorobutyl rubber; chlorinated polyethylene elastomers; polyalkylene oxide polymers; ethylene vinyl acetate; fluorosilicone rubbers; hexafluoropropylene-vinylidene; tetrafluoroethylene terpolymers; butyl rubbers; polyisobutene; synthetic polyisoprene rubber; silicone rubbers; styrene-butadiene rubbers; tetrafluoroethylene propylene copolymers; and thermoplastic-copolyesters. A cartridge according to claims 22-39, wherein said fluid is an injectable medical fluid. A cartridge according to claim 40, wherein said injectable medical fluid is diagnostic contrast media.

Inventors: GABBARD MARK E, GABBARD TIMOTHY J, NIEDOSPITAL JOHN J JR, GABBARD, MARK E., GABBARD, TIMOTHY J., NIEDOSPITAL, JOHN J. JR.
Applicants: BRACCO INT BV, BRACCO INTERNATIONAL B.V.
Application year: 1998
Main classification: A61M5
IPC codes: A61M5