SYRINGE WITH SELF-RETURNABLE PLUNGER

• US 3,738,539 A
• Filed: 06/03/1971
• Issued: 06/12/1973
• Est. Priority Date: 05/08/1970
• Status: Expired due to Term

• Current Assignee: Baxter International Inc.
• Original Assignee: Frank R. Beich
• Inventors: Beich, Frank R.
• Primary Examiner(s): Coleman, Samuel F.
• Assistant Examiner(s): Kocovsky, Thomas E.
• Application Number:
  US05/149,486
• Time in Patent Office: 740 Days
• Field of Search: 222/386.5,341,371 128/218PA,218F,234,235
• US Class Current: 222/341
• CPC Class Codes: A61M 3/00 Medical syringes, e.g. enemata; Irrigators A61M5/00 takes precedence; pistons A61M5/315

Abstract

A plunger-type syringe is provided in which the plunger returns after it is depressed. The syringe includes an elastic membrane which is received by the tubular barrel and interposed between the barrel and the plunger. The open rear end of the barrel is provided with a plurality of circumferentially spaced rearwardly extending pointed projections, and a portion of the membrane extends over the projections and is secured against longitudinal movement thereby. Another portion of the membrane is engaged by the plunger for longitudinal movement with the plunger within the barrel, and as the plunger is depressed, the membrane is stretched and provides a force tending to return the plunger to its original position. When the plunger is released, the elastic membrane returns the plunger.

Claims

1. A syringe comprising an integrally molded elongated tubular barrel having a generally cylindrical wall having an open rear end and terminating in a plurality of circumferential spaced rearwardly extending pointed projections, an elongated plunger slidably disposed in the barrel and projecting from the open rear end thereof, a stretchable elastic membrane extending between the barrel and the plunger, the membrane including a barrel-attaching portion having an annular rear wall extending radially outwardly adjacent the pointed projections and a cylindrical outer wall extending forwardly from the annular rear wall along the outer surface of the wall of the barrel and a plunger-attaching portion engaging the plunger for longitudinal movement therewith within the barrel, the points of the projections digging into the annular rear wall of the membrane as the plunger is moVed forwardly within the barrel to anchor the barrel-attaching portion.

2. A syringe having an elongated tubular barrel with an open rear end and an orifice at the front end, a plunger slidably disposed in the barrel and projecting from the open rear end thereof, a stretchable elastic membrane extending between the barrel and the plunger, the membrance including a first portion engaging the barrel at the rear end thereof and being restrained against longitudinal movement thereby, a second portion engaged by the plunger for longitudinal movement therewith, the membrane being stretchable toward the front end of the barrel as the plunger is moved longitudinally toward the front end of the barrel, the rear end of the barrel terminating in a plurality of rearwardly extending relatively sharp projections engaging the first portion of the membrane to hold the first portion of the membrane as the membrane is stretched toward the front end of the barrel.

3. The syringe of claim 2 in which the tubular barrel includes a generally cylindrical wall and the projections extending longitudinally from the wall at circumferentially spaced locations therearound.

4. The syringe of claim 2 in which the first portion of the membrane includes an annular rear wall extending radially outwardly adjacent the projections on the rear end of the barrel and an outer wall extending longitudinally from the annular rear wall along the outside of the barrel, the projections engaging the annular rear wall for anchoring the first portion of the membrane as the plunger and the second portion of the membrane move toward the orifice of the barrel.

5. The syringe of claim 2 in which the barrel is formed of molded plastic and includes a generally cylindrical wall and the projections are molded integrally with the wall and extending longitudinally from the wall at circumferentially spaced locations therearound.

6. The syringe of claim 5 in which each projection is generally pyramidal and includes an arcuate generally triangular surface extending longitudinally from the outer surface of the cylindrical wall of the barrel and having a pair of inclined side edges terminating in a pointed apex, and a pair of substantially planar generally triangular surfaces, each planar surface extending from one of the inclined side edges and intersecting the other plan surface along a line extending from the inner surface of the barrel to the apex.

7. The syringe of claim 6 in which each inclined side edge of each projection intersects an inclined side edge of the adjacent projection.

8. The syringe of claim 6 in which the included angle between the inclined side edges of each projection is about 45* to about 60*.