Syringe seals and piston

Claim 2

A hypodermic syringe structure comprising a barrel open at one end, a plastic stopper piston in said barrel movable in one direction to develop hydraulic pressure expelling fluid from the barrel, said stopper having a plastic body with means for making sealing engagement with said barrel, said body having a tubular portion extending axially in a direction opposite said one direction, said tubular portion having an open end and a plastic diaphragm extending across and closing said tubular portion inward from said open end in position to be punctured, a hub movable relative to the piston, a hypodermic needle fixed in said hub and having one end projecting from said hub and received in said tubular portion and puncturing said diaphragm as said one end of the needle is moved into said open end and having a second end projecting oppositely from said hub for injecting fluid, said stopper including the body, tubular portion and diaphragm being injection molded inert flexible thermoplastic which does not have the self sealing properties of rubber as the needle is forced through the diaphragm to establish communication between the needle and the contents of the barrel, a first axially facing sealing surface on the open end of said tubular portion, a second sealing surface on the hub presented to said first sealing surface, said sealing surfaces surrounding the needle and means clamping said body and hub axially to bring said sealing surfaces together into sealing engagement for stopping leakage around the needle in case the diaphragm does not seal around the needle when it is punctured.

Claim 3

The structure of claim 1 in which said body has a closed end the outer edge of which is integral with one edge of a rim extending axially in a direction opposite said one direction and the means for making sealing engagement with said barrel is on the axially spaced from said one edge of said rim.

Claim 4

The structure of claim 2 in which the means for making sealing engagement with the barrel comprises a flange integral with a portion of said rim spaced axially from its said one edge, said flange being inclined outwardly from the axis of the barrel and forwardly in said one direction into sliding contact with the bore of the barrel, said flange providing a fluid-tight seal both when fluid in the barrel is under pressure to expel fluid from the barrel, and under static conditions during shipping and storage by reason of the following factors: a. the outer edge of the flange is thick enough to sustain the sealing pressure under static conditions and of outside diameter greater than the inside diameter of the bore of the barrel before it is inserted into the barrel, and b. the flange is of such stiffness that the deflection of the flange alone, when fitted inside the barrel without any other separate parts, results in sealing pressure to maintain a fluid-tight seal under static conditions so that the seal formed thereby is suitable for a syringe which is to be shipped assembled, containing the fluid to be dispensed.

Claim 5

The structure of claim 1 in which the second sealing surface is a taper on the hub.

Claim 6

The structure of claim 1 in which the means clamping said body and hub axially comprise another tubular portion on said body which surrounds and is spaced radially outward from the first tubular portion and interengaging screw threads on the said other portion of said hub.

Claim 7

The structure of claim 5 in which the screw threads on the hub are on a socket telescoped over said other tubular portion.

Claim 8

The structure of claim 1 in which the means for making sealing engagement with said barrel comprises a plastic flange which is inclined outwardly from the axis of the barrel and forwardly in said one direction into sliding contact with the bore of the barrel, said flange providing a fluid-tight seal both when fluid in the barrel is under pressure to expel fluid from the barrel, and under static conditions during shipping and storage by reason of the following factors: a. the outer edge of the flange is thick enough to sustain the sealing pressure under static conditions and of outside diameter greater than the inside diameter of the bore of the barrel before it is inserted into the barrel, and b. the flange is of such stiffness that the deflection of the flange alone, when fitted inside the barrel without any other separate parts, results in sealing pressure to maintain a fluid-tight seal under static conditions so that the seal formed thereby is suitable for a syringe which is to be shipped assembled, containing the fluid to be dispensed.

Claim 9

The structure of claim 6 in which said body has a reentrant recess formed by said rim and said other tubular portion which receives the upper end of the socket when the screw threads on the hub and socket are engaged.

Claim 10

The structure of claim 3 in which the flange has a thickness of about 0.020 to 0.075 inches.

Claim 11

The structure of claim 7 in which the flange has a thickness of about 0.020 to 0.075 inches.

Claim 12

A hypodermic syringe structure comprising a barrel open at one end, a plastic stopper piston in said barrel movable in one direction to develop a hydraulic pressure to expel fluid from the barrel, said stopper having a plastic body, said body having a closed end and the outer edge of which is integral with one edge of a rim extending axially in a direction opposite said one direction with means on said rim for making sealing engagement with said barrel, an externally threaded axially extending tubular portion within said rim and having one end integral with said closed end, said tubular portion extending from said closed end in the same direction as said rim, a hub having an internally threaded socket mating with the threads on said tubular portion for moving the hub in said one direction relative to the stopper, a hypodermic needle fixed in said hub and having one end projecting from said hub and extending within said tubular portion and having a second end projecting oppositely from said hub for injecting fluid, said closed end having an integral plastic diaphragm in position to be punctured as said hub is moved in said one direction relative to the stopper, said stopper including the body, tubular portion and diaphragm being of injection molded inert flexible thermoplastic which does not have the self sealing properties of rubber as the needle is forced through the diaphragm to establish communication between the needle and the contents of the barrel, and means for making a seal for stopping leakage around the outer surface of the needle in case the diaphragm does not seal around the needle as it is punctured.

Claim 13

A hypodermic syringe structure comprising a barrel open at one end, a plastic stopper piston in said barrel movable in one direction to develop a hydraulic pressure to expel fluid from the barrel, said stopper having a plastic body, said body having a closed end and the outer edge of which is integral with one edge of a rim extending axially in a direction opposite said one direction with means on said rim for making sealing engagement with said barrel, an externally threaded axially extending tubular portion within said rim and having one end integral with said closed end, said tubular portion extending from said closed end in the same direction as said rim, a hub having an internally threaded socket mating with the threads on said tubular portion for moving the hub in said one direction relative to the stopper, a hypodermic needle fixed in said hub and having one end projecting from said hub and extending within said tubular portion and having a second end projecting oppositely from said hub for injecting fluid, said closed end having an integral plastic diaphragm in position to be punctured as said hub is moved in said one direction relative to the stopper, said stopper including the body, tubular portion and diaphragm being of injection molded inert flexible thermoplastic which does not have the self sealing properties of rubber as the needle is forced through the diaphragm to establish communication between the needle and the contents of the barrel, and means for making a seal for stopping leakage around the outer surface of the needle in case the diaphragm does not seal around the needle as it is punctured.

Claim 14

The structure of claim 11 in which the means on said rim for making sealing engagement with said barrel comprises a plastic flange integral with and diverging outward from a portion of said rim axially spaced from said one edge of the rim at an acute angle toward the barrel, the unstressed diameter of the outer edge of the flange being greater than the inside diameter of the barrel so the outer edge of the flange is compressed by the barrel and the thickness of the flange being sufficient to provide a liquid tight seal between the outer edge of the flange and the barrel solely by said deflection of the flange due to the inherent resilience of the flange.

Claim 15

The structure of claim 12 in which the flange has a thickness of about 0.020 to 0.075 inches.