Self-aspirating hypodermic ampule

Claim 2

A self-aspirating hypodermic ampule comprising: a. an ampule cylinder; b. a piston formed of resilient material including: a central elongated imperforate core occupying approximately half the internal diameter of the ampule cylinder; a series of annular flanges integrally connected to the core, each flange having an axial length approximating its radial dimension and each said annular flange having an outer diameter normally larger than the internal diameter of the ampule cylinder, whereby the flanges are under radial compression when the piston is received therein; said flanges, when subjected to a first axial force insufficient to effect sliding movement of the piston in the ampule cylinder, being caused to undergo resilient distortion to displace an initial quantity of fluid from the ampule cylinder, and, upon release of said force, to restore to their normal configuration thereby to aspirate the previously discharged quantity of fluid.

Claim 3

A self-aspirating piston, as defined in claim 1, wherein: a. the surfaces of the flanges are essentially trapezoidal in radial section.

Claim 4

A self-aspirating piston, as defined in claim 2, wherein: a. the radially inner peripheries of the flanges have a lesser axial extent than their radially outer peripheries.

Claim 5

A self-aspirating piston, as defined in claim 2, wherein: a. the radially inner peripheries of the flanges have a greater axial extent than their radially outer peripheries.

Claim 6

A self-aspirating piston, as defined in claim 2, wherein: a. the core is solid from end to end, and on radial compression, the piston ends assume a convex contour; one end, on application of an axial force thereon, tending to flatten, causing the opposite end to increase its convex contour to effect liquid displacement.

Claim 7

A self-aspirating piston, as defined in claim 2, wherein: a. the surfaces of the flanges define converging essentially conical surfaces; b. and on application of said first axial force to effect displacement of liquid from the ampule cylinder, one surface of at least a selected flange becomes increasingly conical and its corresponding side is subject to decreasing radial compression; whereas, the opposite surface of said flange becomes less conical and its corresponding side is subject to increasing radial compression; thereby providing a restoring force acting axially on the piston to effect an aspirating movement of the piston.

Claim 8

A self-aspirating hypodermic ampule, comprising: a. an ampule cylinder having a discharge end for a liquid initially contained therein; b. a piston formed of resilient material received in the ampule cylinder and capping the liquid contained therein; the piston having a central core occupying approximately half the internal diameter of said cylinder and presenting essentially flat end surfaces, and a series of annular flanges integral with the core and having a normal outer diameter greater than the ampule cylinder, whereby when the plunger is inserted in the ampule cylinder, the flanges are radially compressed; c. each flange having an axial length and radial depth which are appRoximately equal; d. and a plunger accessible from the end of the ampule cylinder and having an essentially flat end surface for end contact with the piston core to force liquid from the ampule cylinder upon movement of the piston therein; e. the plunger being responsive to a limited axial force to effect resilient distortion of the flanges prior to displacement of the flanges along the ampule cylinder to force an initial quantity of fluid from the ampule cylinder, and upon release of such limited force, to resume their normal configuration thereby to aspirate the previously discharged quantity of fluid.

Claim 9

A self-aspirating hypodermic ampule, comprising: a. an ampule cylinder having a discharge end for a liquid initially contained therein; b. a piston formed of resilient material received in the ampule cylinder and capping the liquid contained therein; the piston having a central core occupying approximately half the internal diameter of said cylinder and presenting essentially flat end surfaces, and a series of annular flanges integral with the core and having a normal outer diameter greater than the ampule cylinder, whereby when the plunger is inserted in the ampule cylinder, the flanges are radially compressed; c. each flange having an axial length and radial depth which are appRoximately equal; d. and a plunger accessible from the end of the ampule cylinder and having an essentially flat end surface for end contact with the piston core to force liquid from the ampule cylinder upon movement of the piston therein; e. the plunger being responsive to a limited axial force to effect resilient distortion of the flanges prior to displacement of the flanges along the ampule cylinder to force an initial quantity of fluid from the ampule cylinder, and upon release of such limited force, to resume their normal configuration thereby to aspirate the previously discharged quantity of fluid.