Piezo-Actuated Dispensing Pump for Accurate Droplet Control
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Solution Overview
Problem
Existing positive displacement pumps face challenges with repeatability and accuracy in dispensing small volumes due to mechanical issues like friction and limited working range, particularly in voice coil-driven bellows pumps which require high power and generate heat, and syringe pumps with stepper motors that suffer from mechanical inaccuracies.
Innovation Solution
A positive displacement pump utilizing a linear piezo-motor and a linear encoder for precise positioning, eliminating the need for complex control circuitry and ensuring accurate and repeatable dispensing of small volumes by using a 'walking' linear actuator and direct encoder connection to the movable member, allowing for precise control and self-locking without heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voice coil actuator is used to drive the bellows pump, then the friction is reduced and mechanical accuracy is improved, but high power is required and heat is generated
Solution Approach 1:
The patent replaces the voice coil electromagnetic actuator with a linear piezo-motor, substituting an electromagnetic mechanical system with a piezoelectric mechanical system. The linear piezo-motor uses piezoelectric ceramic elements to generate precise linear motion through expansion and contraction, eliminating the need for electromagnetic fields and continuous power supply, thereby resolving the contradiction between mechanical accuracy and power consumption
2Device complexity
If a stepper motor with lead screw is used in a syringe pump, then the structure is simple, but mechanical play and friction cause poor repeatability for small droplets
Solution Approach 1:
The patent replaces the stepper motor and lead screw mechanical transmission system with a linear piezo-motor that directly drives the syringe plunger. This eliminates the lead screw, nuts, and associated mechanical play, providing direct drive with high repeatability while maintaining structural simplicity through the integrated piezoelectric actuator
Solution Approach 2:
The patent introduces a linear encoder as an intermediary measurement device between the linear piezo-motor and the dispensing system. The encoder provides precise feedback on the position of the syringe plunger, enabling closed-loop control that ensures accurate and repeatable dispensing volumes, resolving the repeatability issue
3Reliability
If piezo-material is used to directly compress the bellows, then droplet size repeatability is good, but the working range is limited and the bellows needs frequent re-filling
Solution Approach 1:
The patent employs a linear piezo-motor with multiple piezoelectric ceramic elements that can be dynamically controlled to produce extended linear travel. The motor can operate in different modes (expansion, contraction, and neutral positions) and can be repositioned along its stroke, providing a much larger working range that allows the bellows to dispense many more droplets before requiring re-filling, while maintaining the excellent repeatability of piezoelectric actuation
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 provides precise and repeatable dispensing of small liquid volumes with improved accuracy and reduced mechanical issues, maintaining stability and efficiency throughout the dispensing process, even at low pressures, and eliminates the need for extensive calibration.
Implementation Method 1
A positive displacement pump utilizes a linear piezo-motor and a linear encoder for precise positioning
Implementation Method 2
A flexible bellows is placed centrally in the space defined by the jacket. The bellows may be a nickel/cobalt bellows or fiber reinforced plastic bellows or the like
Data Source
AI summary
A system for accurately dispensing small droplets from a positive displacement pumps is actuated by a linear actuator. Preferably the linear actuator is a piezo-actuator. In a method to use the device the system pressure is stabilized before dispensing a plurality of droplets.