Patent ID: 8105294

Claim:
A variable resistance syringe comprising: a piston set including, a piston head, a piston rod connected at one end to said piston head, and an operational flange connected to said piston rod at the other end thereof; and a syringe barrel operable to receive said piston head at a first end thereof and to dispense a fluid from said syringe barrel from a second end thereof, said syringe barrel having a fluid capacity of approximately twenty millimeters or less, said syringe barrel having a first interior projection extending laterally into the interior of said syringe barrel, and said syringe barrel having a second interior projection extending laterally into the interior of said syringe barrel and being axially spaced from said first interior projection downstream of said first interior projection within said syringe barrel, said first interior projection within said syringe barrel offering a sliding resistance force to travel of said piston head within said syringe barrel of a magnitude of F 1 and said second interior projection within said syringe barrel offering a sliding resistance force to travel of said piston head within said syringe barrel of a magnitude of F 2 , and the relative magnitude of the forces F 1 and F 2 within the syringe barrel when the piston head is traveling at a speed of approximately one hundred millimeters per minute satisfies by the following relationship: 1.5 F1<F2<3F1.