Anti-backup improvement for hypodermic syringes
AssigneeEli Lilly and Company
InventorDale C. Harris
Life of this patent
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Abstract
The present invention provides an improved device for preventing the backing up of a nut on a threaded piston rod in the barrel of a hypodermic syringe at the end of dose administration from such syringe. The preferred device is a pawl mounted on the end of a flexible arm of a nut which cooperates with slots on the inside of a syringe barrel. The nut also has an incline surface at the end which mates with an incline surface in the barrel end. The mating of these surfaces at the end of dose administration forces the pawl into a slot, thereby preventing rotation of the nut in the wrong direction and the concurrent movement of the nut up the piston rod associated therewith.
Claims3
An improved device for preventing the backing up of a nut on a threaded piston rod in a barrel of a hypodermic syringe at the end of a dose comprising a pawl means on the nut which cooperates with a rachet means within the barrel and a means on the nut which cooperates with a means in the barrel for forcing the pawl means into the rachet means at the end of the dose to prevent rotation of the nut in the opposite direction to the dose setting direction.
Dependencies are inferred from the claim text.