A single use hyperdermic syringe (20) having a one-way valve (56, 62) to prevent refilling and a retractable needle (30). A needle connector (26) and a needle hub (28) with needle (30) form an assembly (40) with a cavity (52) for the passage of liquid. An elastically-deformable sealing ring (56) and a movable sealing member (62) in the cavity are configured to form a seal, after a single use of the syringe, against a flow of liquid into the syringe barrel (22). Locking pins (76) on the piston engage the needle connector when the barrel is emptied, whereby the needle is retractable into the barrel by moving the plunger (24) in the proximal direction.

DETAILED DESCRIPTION

Referring first toFIGS. 1 to 6, which show a first embodiment of the safety syringe, the single use hypodermic syringe20includes a barrel22, a plunger24, a needle connector26and a needle hub28with a hypodermic needle30affixed to it. The barrel22has a barrel wall23defining a bore25. The barrel has a radially outward outwardly-extending finger flange27at its proximal end. The plunger24includes a plunger shaft or rod29, a piston31at its distal end and a thumb rest35at its proximal end. The plunger shaft is cross-vaned in structure. An O-ring68on the piston31forms a fluid seal against the inner surface of the barrel wall23.

The needle connector26is located at the distal end of the barrel22and has a first portion32lying within the bore and a second portion33which extends out of the opening34in the distal end of the barrel. The radially outer surface36of the first portion33of the needle connector sealingly engages against the inner surface38of the barrel wall, such that fluid in the barrel bore25cannot escape between them. The radially outer surface36of the needle connector and the inner surface38of the barrel wall are, at their point of engagement, con- toured to create a releasable snap-fit of the needle connector within the barrel. The snap-fit mechanism is such that the needle connector can be withdrawn into the barrel for purposes of sheathing the needle, as described below, but it is sufficiently strong to prevent movement of the needle connector during the manufacturing process, shipping, or during the filling and injection steps that occur during use of the syringe.

The needle connector26has a channel42which extends from the proximal side44of the needle connector to its distal side46. The channel42has an enlarged portion48adjacent to the proximal side44, with two circumferential grooves50, for engaging the plunger latching members, as described below.

The needle connector26and needle hub28attach securely together by means of circumferentially-disposed ribs39on the needle connector which interfit tightly with mating grooves41on the needle hub. Thus, when the needle connector is withdrawn into the barrel, the needle hub and needle are likewise retracted. The needle connector and the needle hub, being affixed together, form an assembly40having a cavity52therein. Part of the cavity comprises the channel42extending between the proximal and distal faces of the needle connector. Another part of the cavity52is the portion53, within the needle connector, configured to hold the annular base portion54of the sealing ring56. Another part of the cavity52is the portion55within the needle hub, between the distal end of the needle connector and the proximal end of the needle.

The sealing ring56has an elastically-deformable, inwardly- extending sealing portion58, extending from the annular base portion54, having an opening60therein. A movable sealing member62has a shaft portion64and a head portion66. The shaft portion is posi- tioned in the channel42of the needle connector. The head66of the movable sealing member has a diameter larger than the diameter of the opening60of the sealing ring56. The sealing portion58of the sealing ring is distally inwardly inclined and is elastically deformable such that the head66of the movable sealing member can pass through the opening60in the distal direction, and pass into the portion55of the cavity52in the needle hub under the pressure of liquid caused when the plunger in the syringe is moved in the distal direction.

The channel42in the needle connector26has four longitudinally-extending grooves43along the sides of the part of the channel42that accommodates the movable sealing member62. The grooves permit the flow of liquid along the channel42past the sealing member62. Thus, liquid can flow through the channel42for filling the syringe and for injection. In the cavity portion55in the needle hub, channels57are provided in the cavity walls, adjacent to the distal end of the cavity, to permit the flow of liquid past the head66of the sealing member when the head66is in the cavity portion55.

Two locking pins76extend distally from the distal face78of the piston, proximate to its center, and aligned with the opening70of the channel42at the proximal side of the needle connector. The locking pins76are sized and positioned such that, when the distal face78of the piston is brought into contact with the proximal side44of the needle connector, the locking pins76are within the enlarged portion48of the channel42and the two ribs80on the radially outer surfaces of the locking pins are fitted in respective grooves50of the channel42, in a snap-fit engagement therewith.

The barrel22is designed to prevent removal of the needle after use. A circumferential groove82and lip84are provided in the inner surface of the barrel wall23close to its proximal end, to engage the radially outer periphery36of the needle connector and the O-ring respectively, when the plunger is retracted after use. A frangible or weakened portion86of the plunger shaft29is provided to permit the shaft to be broken off by a user when the needle is retracted to the locked position within the barrel.

For initial filling of the syringe, the sealing member62is on the proximal side of the sealing ring56, as shown inFIG. 2. Liquid can then be drawn into the barrel bore by movement of the plunger in the proximal direction, the liquid passing through the needle into the cavity portion55, through the opening60in the sealing ring56, through the channel42in the needle connector26and into the barrel bore. When the plunger is then pressed in the distal direction to inject the liquid, the liquid flows from the barrel bore through the channel42, pressing against the proximal side of the sealing portion58of the ring56and against the proximal end of the movable sealing member62. This pressure causes the opening60of the sealing ring56to enlarge and permit the head66of the movable sealing member62to be pushed through the opening and also permit the liquid to flow through the opening60in the distal direction, through the cavity portion55in the needle hub and out through the needle. This position is shown inFIG. 4.

From this point, movement of the movable sealing member62in the proximal direction is stopped by the engagement of the sealing portion58of the ring56with the head66of the movable sealing member. The sealing portion58, and more specifically its sealing surface90around the opening60, seals against the head66, stopping any flow of liquid in the proximal direction. The sealing member and sealing ring thus act as a one-way valve in the syringe, a mechanism which does not require that the plunger be in the fully inserted position in order to prevent refilling. As the plunger is pushed farther to complete the injection, emptying the barrel, the locking pins76enter the enlarged portion48of the channel42of the needle connector. The ribs80lock into the grooves50of the channel42. The needle connector26is thus securely attached to the plunger24, as illustrated inFIG. 5.

The plunger24is then retracted. As the plunger is moved in the proximal direction, the snap-fit attachment of the needle connector to the barrel wall23at the distal end of the barrel is overcome, permitting the needle connector to be withdrawn into the barrel bore, bringing with it the attached needle hub, and thus withdrawing the needle into the bore. This position is shown inFIG. 6. The plunger is withdrawn until the radially outer periphery36of the needle connector and the O-ring68engage the barrel circumferential groove82and circumferential lip84respectively, locking the plunger in place. The length of the needle is such that the needle is now in a fully retracted position within the barrel bore. The user then breaks off at the weakened point86the portion of the shaft extending beyond the proximal end of the barrel. The syringe may then be safely discarded.

A second embodiment of the safety syringe is shown inFIGS. 7 to 9. The syringe200is essentially the same as the syringe20described above, except for the mechanism for locking together the needle connector and the plunger, and a structure for minimizing the volume of liquid left in the syringe after use.

The distal face78of the plunger has four locking pins202disposed at its periphery and extending distally and equally spaced apart. Each locking pin202has a leg204and an inwardly-extending hook portion206. A projecting member, cylindrical post208, extends distally from the center of the face78. The needle connector26has four peripheral recesses210, sized and spaced to be engaged by respective locking pins202, with a lip212for engagement by the hook206of the pin202. The channel42of the needle connector has an enlarged portion48sized to receive the post208of the plunger.

When the plunger is moved distally to engage the needle connector, the sloping surface214on the top of the resilient pins202causes the pins to be bent outwardly, into the space between the pins and the barrel wall23. The pins resile inwardly as the hooks206fit around the lip212of the needle connector recesses. The post208of the plunger then occupies the volume of the channel enlargement48, thus minimizing the volume of liquid left in the needle connector after use.

A third embodiment of the safety syringe is shown inFIGS. 10 to 12. The syringe300is essentially the same as the syringe20described above, except for the mechanism for locking together the needle connector and the plunger, and a structure for minimizing the volume of liquid left in the syringe after use.

The distal face78of the plunger has ten locking pins302disposed radially inwardly of its periphery and extending distally. The locking pins are arranged in four sets around a distally-extending post308. Two opposed sets have four locking pins each. The other two opposed sets have a single locking pin each. Each locking pin302has an outwardly-projecting hook332subtended by a sloping surface334on the outward surface of the pin.

The needle connector326has an annular member316that is spaced by a radially-extending slot318from a flange320. The annular member316is joined to the flange320by four connectors322, dividing the slot318into four segments.

The needle connector326has a cylindrical wall324extending distally from its proximal end, the wall324defining a first enlarged portion338of the channel42of the needle connector. The wall324is radially spaced from the annular member316and the flange320by an axially-extending annual groove330, which is sized to receive the locking pins302.

The post308on the distal face of the piston has three sections which are successively smaller in the distal direction and are shaped to be received within respective sections of the channel42of the needle connector. The first section336, being the largest in diameter, fits within the first section338of the channel; the second section340of the post308fits within the second section342of the channel; and the third section344of the post, being the smallest in diameter, fits within the smallest section346of the channel.

When the plunger is moved distally to engage the needle connector, the sloping outer surface334of the locking pins slides over the inner face of the annular member316, causing the locking pins to bend inwardly. As the hooks fit into the slot318the pins resile outwardly so that the hooks engage the annular member316. The spacing of the locking pins302and of the connectors322is such that, although some pins may align with a connector and not engage in the slot318, at least four pins will engage in the slot, irrespective of the orientation of the plunger, forming a sufficiently secure attachment between the plunger and the needle connector for retraction of the needle.

In the locked position, the post308of the plunger occupies the volume of the three sections338,342,346of the channel42, minimizing the volume of liquid left in the needle connector after use.

The components of the syringe may be made of any suitable materials. Such materials include polystyrene, polypropylene or polyethylene for the needle connector and the needle hub, acrylonitrile butadiene styrene (ABS) for the movable sealing member, thermoplastic elastomer (TPE) for the sealing ring, and polypropylene for the barrel and plunger.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the scope thereof.

LIST OF REFERENCE NUMERALS IN THE DRAWINGS

20syringe22barrel23barrel wall24plunger25bore of barrel26needle connector27flange of plunger28needle hub29shaft of plunger30needle31piston32first portion of needle connector33second portion of needle connector34opening in distal end of barrel35thumb rest of plunger36outer periphery of needle connector38inner surface of barrel wall39ribs on needle connector40assembly of needle connector and needle hub41grooves on needle hub42channel in needle connector43longitudinal grooves along channel4244proximal side of needle connector46distal side of needle connector48enlargement in channel4250radial grooves in channel4252cavity in assembly53cavity portion for sealing ring54annular base of sealing ring55cavity portion in needle hub56sealing ring57channels in cavity portion5558sealing portion of sealing ring60opening in sealing portion of sealing ring62movable sealing member64shaft of movable sealing member66head of movable sealing member68O-ring70opening at distal end of channel4276locking pins78distal face of plunger80ribs on locking pins82groove in barrel wall84lip in barrel wall86frangible portion of plunger shaft90sealing surface of sealing ring200syringe (second embodiment)202locking pins204leg of locking pin206hook of locking pin208post on distal face of piston210peripheral recesses of needle connector212lip of peripheral recess214sloping surface of locking pin300syringe (third embodiment)302locking pins308post on distal face of piston316annular member of needle connector318radial slot in needle connector320flange322connectors324cylindrical wall of needle connector326needle connector330annular groove in needle connector332hook of locking pin334sloping outer surface of locking pin336first section of post308338first section of channel42340second section of post342second section of channel344third section of post346third section of channel