Infusion Pump Feed Screw Nut Structure for Misalignment Compensation
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Solution Overview
Problem
Existing drive devices for medical infusion pumps face challenges in achieving high accuracy in the movement of guided members due to misalignment between the screw portion and the feed screw, which can be exacerbated by thermal expansion and manufacturing errors.
Innovation Solution
The drive device incorporates a guided member with a nut member that has a bearing portion with an elongated hole shape, allowing the screw portion to move in both directions towards the central axis and intersecting directions, and includes a pair of nut members sandwiching the feed screw, a cam for switching positions, and biasing members to improve alignment and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the screw portion is fixed in position relative to the nut member, then the structure is simple, but misalignment occurs due to thermal expansion and manufacturing errors, reducing movement accuracy
Solution Approach 1:
The screw portion is made movable within the nut member through a groove structure, allowing dynamic adjustment to compensate for thermal expansion and manufacturing errors. The groove enables the screw portion to shift position while remaining constrained, transforming a static fixed connection into a dynamic adaptive connection that maintains alignment accuracy under varying conditions.
2Manufacturing precision
If the screw portion can move in multiple directions, then misalignment is reduced, but the control complexity increases
Solution Approach 1:
The groove is designed with specific geometric characteristics - elongated in a direction intersecting the radial direction - to provide freedom of movement only in the necessary directions for compensation while maintaining constraint in other directions. This localized geometric design enables selective mobility that reduces misalignment without requiring complex control mechanisms.
Data Source
AI summary
A drive device includes: a feed screw configured to rotate about a central axis; and a guided member configured to be guided in an axial direction along the central axis, wherein the guided member includes at least one nut member having a screw portion screwed with the feed screw. In a transverse section orthogonal to the central axis, the screw portion is configured to move in both a first direction toward the central axis and a second direction intersecting the first direction.