Inline Dispense Pump Anti-Backlash Assembly for Precise Dosing
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Solution Overview
Problem
Existing inline piston pumps suffer from mechanical backlash, leading to inaccuracies in fluid dispensing due to 'step loss', which cannot be effectively addressed through software calibration without modifying existing pump control software, a task beyond the control of pump manufacturers.
Innovation Solution
An inline fluid dispense pump assembly with mechanical anti-backlash mechanisms, including a spring-loaded mechanism and a linear slide with ball bearings, prevents rotational movement of the lead screw and piston, ensuring accurate fluid dispensing without software intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a lead screw mechanism is used to convert rotational motion to linear motion in the pump, then the pump can achieve mechanical actuation of the piston, but mechanical backlash in the lead screw causes step loss and reduces dispensing accuracy
Solution Approach 1:
The patent applies preliminary anti-action by pre-loading the lead screw mechanism with a spring mechanism that maintains constant contact pressure between the lead screw threads and the nut, eliminating backlash before it can affect dispensing accuracy. This pre-applied counterforce ensures that the mechanical connection remains tight during bidirectional motion.
Solution Approach 2:
The patent introduces an intermediary ball bearing mechanism between the lead screw and the nut that eliminates direct thread-to-thread contact. The ball bearings act as mediators that reduce friction and eliminate backlash while maintaining the mechanical coupling needed for actuation, thereby resolving the contradiction between mechanical operation and precision.
2Measurement precision
If software calibration is used to compensate for backlash, then dispensing accuracy can be improved, but this requires modifying existing pump control software which is beyond the control of pump manufacturers
Solution Approach 1:
The patent replaces the software-based compensation approach with a purely mechanical solution. By implementing a pre-loaded anti-backlash mechanism through spring-loaded lead screw engagement and ball bearing intermediaries, the system eliminates the need for software calibration entirely, maintaining precision through mechanical design alone.
3Ease of operation
If a shaft key or splined shaft is used to prevent lead screw rotation, then linear motion can be achieved, but play in the system results in inaccuracies when direction of motion is reversed
Solution Approach 1:
The patent applies dynamics by using a spring-loaded mechanism that dynamically adjusts the contact pressure between the lead screw and nut during operation. The spring force automatically increases during direction reversals to maintain tight engagement, adapting to the changing mechanical conditions and eliminating play that would cause inaccuracies.
Solution Approach 2:
The patent utilizes controlled mechanical vibration through the spring mechanism that creates high-frequency micro-movements in the lead screw engagement. This vibration helps maintain constant contact between mating surfaces, preventing the development of play and ensuring accurate positioning during direction reversals.
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
Achieves precise fluid dispensing with minimal backlash, maintaining accuracy within +/- 10 picoliters without requiring software modifications, by mechanically eliminating rotational movement in the pump assembly.
Implementation Method 1
The linear slide includes a rail having a slide block thereon. The linear slide and rail are engaged to prevent rotation of the slide about an axis perpendicular to the longitudinal axis of the rail.
Implementation Method 2
An inline fluid dispense pump assembly with mechanical anti-backlash mechanisms, including a spring-loaded mechanism and a linear slide with ball bearings, prevents rotational movement of the lead screw and piston
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
An inline pump assembly for dispensing fluids, the pump assembly including a pump head (12), having a piston (16) wherein movement of the piston causes the pump head to dispense a fluid. A linear actuator (20) has a lead screw (26) wherein actuation of the linear actuator causes the lead screw to move along a linear path. A first anti-backlash device (33) is disposed between the linear actuator and the pump head. The anti-backlash device includes a rail (32) having a sliding block (34) thereon. The slide block and rail are engaged to prevent movement of the slide block about a longitudinal axis of the rail. A coupler (50) is fixedly secured to the linear slide (30) and having a first end connected to the lead screw and a second end connected to the piston rod.