Lead Screw Thread Alignment for Syringe Pump Infusion Accuracy
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Solution Overview
Problem
Existing syringe pump systems often experience delayed or excessive fluid infusion due to misalignment of split nut threads and lead screw threads during syringe replacement, particularly at low infusion rates, leading to inaccurate and imprecise fluid delivery.
Innovation Solution
A system that includes a motor coupled to the lead screw, a plunger driver, a position sensor, and a processor to automatically align the threads of the screw drive mechanism with the lead screw threads, ensuring full engagement by rotating the lead screw to a predetermined position based on position signals from the sensor, thereby reducing thread misalignment and improving infusion accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If manual alignment of split nut threads with lead screw threads is used during syringe replacement, then device complexity is reduced, but thread engagement precision deteriorates leading to delayed fluid infusion
Solution Approach 1:
The patent replaces manual mechanical alignment with an automated sensor-based detection and correction system. A position sensor detects the axial position of the screw drive mechanism, and a processor automatically calculates and executes the precise lead screw rotation needed to align threads, substituting human judgment with automated measurement and control.
Solution Approach 2:
The system performs self-alignment by automatically detecting its own positional state through the position sensor and correcting any misalignment through automated lead screw rotation. The system serves itself by identifying and resolving its own alignment issues without external intervention.
2Manufacturing precision
If automatic lead screw rotation is performed to ensure full thread engagement, then thread engagement precision is improved, but infusion time increases due to additional rotation required
Solution Approach 1:
The system performs preliminary detection of the axial position using the position sensor before syringe replacement is completed. By knowing the starting position in advance, the system can calculate the exact rotation needed and execute it efficiently, preventing delays rather than reacting to misalignment after the fact.
Solution Approach 2:
The position sensor provides continuous feedback about the axial position of the screw drive mechanism to the processor. This feedback loop enables the system to make precise, data-driven decisions about the amount of rotation needed, avoiding both insufficient alignment and excessive rotation that would waste time.
3Reliability
If fixed amount of lead screw rotation is applied to remove thread clearance, then thread engagement reliability is improved, but infusion accuracy deteriorates due to excessive fluid infusion
Solution Approach 1:
The system dynamically adjusts the rotation parameter based on the detected axial position. Instead of applying a fixed rotation amount that may be excessive or insufficient, the processor calculates the precise rotation needed to achieve full thread engagement, changing the rotation parameter to match the actual system state and preventing over-infusion.
Data Source
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AI summary
A system and method for automatically aligning the threads of a lead screw with the threads of a screw drive mechanism, the screw drive mechanism operating to translate the rotational motion of the lead screw into linear motion to expel the contents of a mounted syringe. The system comprises a driver position sensor for determining the position of the screw drive mechanism along the lead screw and a processor for receiving position signals from the driver position sensor, for determining a requisite rotation of the lead screw to ensure alignment of the two sets of threads, and for effectuating the requisite rotation of the lead screw to achieve that alignment. An automatic calibration routine is included that checks for variances in calibration of the system and if found, updates a conversion factor to restore accuracy. Various sensors are used to monitor the operation of components.