Patent ID: 8622962

Claim:
A safety syringe comprising: a barrel that contains a predetermined volume of fluid, and having an inner wall, a proximal end, a distal end and a longitudinal axis; a plunger assembly including a proximal plunger section having proximal and distal ends, and an interconnected distal plunger section having proximal and distal ends; the distal plunger section including a piston at the distal end of the distal plunger section and that provides a substantially fluid-tight slidable seal with respect to the inner wall of the barrel; the proximal plunger section including, at the proximal end thereof, a cavity for matingly receiving the proximal end of the distal plunger section for relative motion therebetween; a ratcheting mechanism constructed and arranged to provide a tactile feedback in response to direction of the piston against the fluid so as to generate a backpressure in excess of a predetermined maximum pressure, the tactile feedback being provided each of a predetermined number of times; the ratcheting mechanism including a plurality of wedge-shaped ramps constructed and arranged as steps in a direction of the longitudinal axis and disposed at the proximal end of the distal plunger section; the ratcheting mechanism further including at least one ratchet arm that is peripherally disposed and extends distally at the distal end of the proximal plunger section; the ratchet arm including a distal pawl for conforming engagement with a corresponding wedge-shaped ramp; a thumb plate disposed at the proximal end of the proximal plunger section; and a stop secured to the inner wall of the barrel forming a projection against which a distal pawl end of the ratchet arm engages subsequent to disconnection of the distal plunger section from the proximal plunger section.