Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1998-03-02
2001-05-01
Yasko, John D. (Department: 3734)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S222000
Reexamination Certificate
active
06224577
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to syringes and plungers for use therein, and more particularly, to syringes and plungers for use therein in which lubricant need not be applied between the syringe and the plunger.
BACKGROUND OF THE INVENTION
In many medical procedures, such as drug delivery, it is desirable to inject a fluid into a patient. Likewise, numerous types of contrast media (often referred to simply as contrast) are injected into a patient for many diagnostic and therapeutic imaging procedures. For example, contrast media are used in diagnostic procedures such as X-ray procedures (including, for example, angiography, venography and urography), CT scanning, magnetic resonance imaging (MRI), and ultrasonic imaging. Contrast media are also used during therapeutic procedures, including, for example, angioplasty and other interventional radiological procedures. Regardless of the type of procedure, any fluid injected into the patient must be sterile and contain a minimum of pyrogens.
Typically, a fluid is injected into a patient using a manual or powered syringe. Such syringes typically comprise a reciprocally slidable plunger disposed within a cylindrical syringe body.
A number of injector-actuated syringes and powered injectors for use in angiography, computed tomography and NMR/MRI have been developed. In general, syringe plungers for use with such powered injectors require an elastomeric cover which forms a sealing engagement with the inner wall of the syringe barrel. To reduce friction and provide an adequate seal, the syringe barrel, the plunger and the elastomeric plunger cover are typically lubricated during manufacture with, for example, a silicone oil lubricant. U.S. Pat. Nos. 4,628,969 and 4,718,463 describe such lubrication.
The requirement of application of a silicone lubricant oil adds a step in the manufacturing process. Moreover, there is a risk that small amounts of silicone oil can be injected into the patient.
It is desirable to develop a syringe and a plunger for use therein in which an adequate seal is formed therebetween without the need for applying lubrication between the syringe and plunger.
SUMMARY OF THE INVENTION
The present invention provides a syringe and a plunger for use therein for injecting a fluid into a patient. In one aspect of the invention, the plunger comprises a pressure member extending around the circumference of a generally cylindrical body of the plunger. The pressure member is in substantially sealing contact with the plunger body. The pressure member is sufficiently flexible to be forced radially outwardly to exert force upon the inner wall of the syringe in response to increased fluid pressure upon forward motion of the plunger (that is, during an injection procedure). The pressure member thereby forms a substantially sealing engagement with the inner wall of the syringe.
In one embodiment, the pressure member comprises a flange attached at a rearward portion thereof to a body of the plunger. The flange extends forward and radially outward to form a circumferential channel between the flange and the body of the plunger. The flange flexes radially outwardly to form a substantially sealing engagement with the inner wall of the syringe in response to increasing fluid pressure within the channel upon forward motion of the plunger.
In another embodiment, the pressure member comprises a resilient O-ring in sealing contact with the body of the plunger. The O-ring is also preferably in sealing engagement with the inner wall of the syringe. The O-ring is seated in a seating formed around the circumference of the body of the plunger. The seating comprises a ramp portion having a forward radius that is smaller than a rearward radius thereof. The ramp portion thus extends radially outward toward the rear thereof. As the plunger is moved forward, frictional contact with the inner wall of the syringe and increasing fluid pressure force the O-ring to move rearward along the ramp portion of the seating. The increasing radius of the ramp portion causes the O-ring to exert greater force upon the inner wall of the syringe, thereby ensuring a substantially sealing engagement between the O-ring and the inner wall.
The pressure members of the present invention, as compared to conventional designs, maintain a substantially sealing contact with the inner wall of the syringe while reducing frictional forces associated with movement of the plunger within the syringe. Moreover, the pressure members of the present invention maintain substantially sealing contact with the inner wall of the syringe even as the syringe expands under increased pressure (that is, increased fluid pressure during injection).
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International Search Report for Counterpart PCT Application No. PCT/US99/03837.
Dedola Salvatore J.
Hitchins Mark W.
Bradley Gregory L.
Medrad Inc.
Yasko John D.
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