Patent ID: 9421327
Filing Date: 2016-08-23
CPC Classification: A61M,F04B

Claim Text:
1. A dosing unit for an infusion pump device, the dosing unit comprising: a piston pump with a pump cylinder; a plunger arranged within the pump cylinder, the pump cylinder and the plunger coaxially arranged along a longitudinal axis; and a separate bias force element; wherein the plunger has a plunger shaft with an outer plunger thread and the pump cylinder has a threaded sleeve part with an inner cylinder thread; wherein the inner thread and the outer thread engage with each other in such a way that a rotational movement of the plunger around the longitudinal axis results in a linear displacement of the plunger along the longitudinal axis; wherein the separate force bias element biases the two threads in regard to each other along the longitudinal axis, such that the threaded engagement of the inner thread and the outer thread is free of play independent of a direction of a rotational movement and linear displacement of the plunger in regard to the cylinder, and wherein the separate bias force element is a half-ring-like metal spring that has a flat portion, and at least one locking structure on an end of the metal spring, the at least one locking structure being located in a recession on an outer wall of the cylinder, and the flat portion being arranged in an opening in the threaded sleeve part of the cylinder and abutting a lateral surface of the outer thread of the plunger shaft, and wherein the separate bias force element subjects the plunger shaft to a force perpendicular to the longitudinal axis, thereby pressing a portion of the plunger thread onto a portion of the cylinder thread.