Infusion Pump Feed Screw Alignment With Dual Nut Guidance
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Solution Overview
Problem
Existing drive devices for medical infusion pumps face challenges in achieving high accuracy of guided member movement due to misalignment of screw portions with respect to the feed screw, which can be exacerbated by thermal expansion and manufacturing errors.
Innovation Solution
The drive device incorporates a pair of nut members with bearing portions that guide the screw portions to move towards the central axis and includes a switching mechanism with a cam and biasing members to maintain alignment, along with position detection sensors to ensure precise screw engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single nut member with screw portion is used, then the structure is simple, but misalignment between screw portion and feed screw occurs due to thermal expansion and manufacturing errors
Solution Approach 1:
The single nut member is divided into two separate nut members, each with its own screw portion. This segmentation allows each screw portion to independently adjust and compensate for misalignment, thereby improving alignment accuracy while maintaining relatively simple structure
Solution Approach 2:
The two nut members are positioned asymmetrically on opposite sides of the feed screw, allowing them to apply compensating forces in different directions to counteract thermal expansion and manufacturing errors, thus improving alignment precision
2Stability of the object's composition
If the screw portion is fixed in position, then the structure is stable, but misalignment cannot be compensated for thermal expansion and manufacturing errors
Solution Approach 1:
The screw portions are made dynamically adjustable through the bearing portions with long holes, allowing them to move and self-align during operation. This dynamic capability enables compensation for thermal expansion and manufacturing errors while maintaining operational stability
Solution Approach 2:
The long hole shape of the bearing portions changes the effective parameters of the screw portion positioning, allowing radial movement to compensate for misalignment. This parameter change enables the system to adapt to thermal expansion and manufacturing variations while maintaining stability
3Device complexity
If the bearing portion has a circular shape, then the screw portion cannot move laterally to reduce misalignment, but the structure is simple
Solution Approach 1:
The bearing portion has different local qualities: the long hole shape provides lateral movement capability in the direction needed for alignment compensation, while maintaining structural simplicity elsewhere. This localized design improvement enhances alignment accuracy without significantly increasing overall complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the accuracy of guided member movement by reducing misalignment, allowing for precise control of the plunger within the syringe, thereby improving the overall performance of the medical infusion pump.
Implementation Method 1
the drive device includes a biasing member that biases the screw portion in a direction toward the central axis... the guided member includes a spring forming the biasing member
Data Source
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AI summary
Provided are a drive device and a medical infusion pump capable of moving a guided member with high accuracy. A drive device includes: a feed screw that rotates about a central axis; and a guided member guided in an axial direction along the central axis. The guided member includes a nut member having a screw portion screwed with the feed screw. The screw portion moves in both a direction toward the central axis and a direction intersecting the direction in a transverse section orthogonal to the central axis. A medical infusion pump includes the drive device.