Remote Stepper Motor Rotary Drive for LC Sample Positioning
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Solution Overview
Problem
Space constraints and thermal control issues in high performance liquid chromatography (HPLC) and ultra performance liquid chromatography (UPLC) systems limit the placement of motors and mechanisms for accurate sample needle positioning, and volatile gas buildup can interfere with motor operation.
Innovation Solution
A rotary drive mechanism with a stepper motor and drive belt or coupling element, where the stepper motor is located outside the sample compartment, and a rotary position encoder is used to control the sample tray's position, reducing leakage and allowing for precise sample needle positioning and mixing of fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the stepper motor is placed inside the sample compartment to directly drive the sample needle positioning mechanism, then the positioning accuracy and response time are improved, but the risk of motor failure due to volatile gas buildup and thermal control issues increases
Solution Approach 1:
The stepper motor is extracted from the sample compartment and placed in the external environment. A shaft extends through the compartment wall to transmit rotational motion from the external motor to the internal sample needle positioning mechanism, thereby isolating the motor from volatile gases and thermal control issues while maintaining positioning accuracy
Solution Approach 2:
A shaft acts as an intermediary element that transmits rotational motion from the stepper motor located outside the sample compartment to the sample needle positioning mechanism inside the compartment. This intermediary allows the motor to operate in a safe external environment while still controlling internal components with the required precision
2Volume of stationary object
If the sample compartment volume is reduced to improve system compactness, then the overall system size is reduced, but the space for thermal control mechanisms and motor placement is limited
Solution Approach 1:
The motor placement problem is solved by transitioning from a two-dimensional layout (within the compartment plane) to a three-dimensional arrangement (extending through the compartment wall). The shaft penetrates the compartment boundary, allowing the motor to be positioned in the external dimension while still driving internal mechanisms, thus resolving the space constraint issue
3Stability of the object's composition
If thermal control of the sample compartment is enhanced to prevent leakage and condensation, then the sample stability is improved, but the motor operation within the compartment becomes more problematic
Solution Approach 1:
The stepper motor is extracted from the thermally controlled sample compartment environment and placed externally. This extraction eliminates the motor's exposure to thermal control effects such as condensation and temperature fluctuations, while the shaft maintains the mechanical connection needed for sample needle positioning
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
The solution enables accurate and repeatable sample positioning, reduces leakage and thermal control issues, and allows for efficient mixing of sample fluids, while maintaining safety by isolating the motor from volatile gases within the sample compartment.
Implementation Method 1
The drive belt engages the pulley and the motor shaft
Implementation Method 2
a rotary position encoder is disposed about the second portion of the shaft
Implementation Method 3
a sample vial containing at least two sample fluids is rotated in a forward direction at a first rotation rate and then rotated in a reverse direction at a second rotation rate
Data Source
AI summary
Described is an apparatus for controlling a position of a sample in a liquid chromatography system. The apparatus includes a rotary drive mechanism, a stepper motor and a rotational coupling system such as a drive belt and pulley system. The rotational coupling system transfers the rotational motion of a motor shaft to a shaft of the rotary drive mechanism. Advantageously, the stepper motor is remote to the sample compartment for improved safety in the event that volatile gas accumulates within the sample compartment. The rotary drive mechanism can be configured in a small form factor and can provide highly stable rotation of an attached sample tray to accommodate the requirements of compact liquid chromatography systems. In addition, leakage from inside the sample compartment to the ambient environment is substantially reduced or eliminated, resulting in better thermal control of the sample compartment.