Dual-compartment hypodermic syringe

Claim 1

A hypodermic syringe comprising: an elongated tubular body centered generally on an axis and having a front end adapted to carry a needle, a rear end spaced axially behind the front end, and a bypass between the ends; a front partition piston defining with the front end a front compartment adapted to hold a substance; a rear piston defining with the front piston a rear compartment adapted to hold a fluid miscible with the front-compartment substance, the front piston being displaceable into a middle position in the bypass for fluid communication between the compartments; a stem projecting axially rearward out of the body form the rear piston and provided with axially spaced front and rear stops and having a clear region between the stops; and damper means on the rear end of the body engageable with the stops for slowing axial movement of the stops past the rear end of the body and permitting relatively rapid axial movement of the stem in the body when the stops axially flank the damper means and the clear region is level with the damper means.

Claim 9

A method of using a hypodermic syringe comprising: an elongated tubular body having a front end adapted to carry a needle, a rear end, and a bypass between the ends; a front partition piston defining with the front end a front compartment adapted to hold a substance; a rear piston defining with the front piston a rear compartment adapted to hold a fluid miscible with the front-compartment substance, the front piston being displaceable into a middle position in the bypass for fluid communication between the compartments; a stem projecting rearward out of the body from the rear piston and provided with axially spaced front and rear stops and having a clear region between the stops; and means including a damper on the rear end of the body engaging the stops for slowing axial movement of the stops past the rear end of the body and for permitting relatively rapid axial movement of the stem in the body when the clear region is level with the damper; the method comprising the steps of sequentially: a) slowly advancing the front stop forward through the damper and thereby pushing the rear piston and front pistons forward until the front piston is level with the bypass; b) rapidly advancing the rear piston forward to force the fluid in the rear compartment axially forward in the bypass past the front piston into the front compartment, whereby the fluid of the rear compartment mixes with the substance of the front compartment; c) rapidly retracting the rear piston backward to draw the mixture from the front compartment through the bypass past the front piston into the rear compartment; d) rapidly advancing the rear piston forward to force the mixture in the rear compartment through the bypass past the front piston into the front compartment; e) repeating steps c) and d) until the substance and fluid are thoroughly mixed; f) slowly advancing the rear stop forward through the damper and thereby pushing the pistons both forward until the front piston is forward of the bypass; and g) rapidly advancing the pistons forward and ejecting the mixture from the front compartment through the front end of the body.

Claim 10

A method of using a hypodermic syringe comprising: an elongated tubular body having a front end adapted to carry a needle, a rear end, and a bypass between the ends; a front partition piston defining with the front end a front compartment adapted to hold a substance; a rear piston defining with the front piston a rear compartment adapted to hold a fluid miscible with the front-compartment substance, the front piston being displaceable into a middle position in the bypass for fluid communication between the compartments; a stem projecting rearward out of the body from the rear piston and provided with axially spaced front and rear stops and having a clear region between the stops; and means including a damper on the rear end of the body engaging the stops for slowing axial movement of the stops past the rear end of the body and for permitting relatively rapid axial movement of the stem in the body when the clear region is level with the damper; the method comprising the steps of sequentially: a) slowly advancing the front stop forward through the damper and thereby pushing the rear piston and front pistons forward until the front piston is level with the bypass; b) rapidly advancing the rear piston forward to force the fluid in the rear compartment axially forward in the bypass past the front piston into the front compartment, whereby the fluid of the rear compartment mixes with the substance of the front compartment; c) rapidly retracting the rear piston backward to draw the mixture from the front compartment through the bypass past the front piston into the rear compartment; d) rapidly advancing the rear piston forward to force the mixture in the rear compartment through the bypass past the front piston into the front compartment; e) repeating steps c) and d) until the substance and fluid are thoroughly mixed; f) slowly advancing the rear stop forward through the damper and thereby pushing the pistons both forward until the front piston is forward of the bypass; and g) rapidly advancing the pistons forward and ejecting the mixture from the front compartment through the front end of the body.