Ball Joint Pusher Plunger Coupling for Syringe Dose Accuracy
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Solution Overview
Problem
Infusion devices face challenges in maintaining accurate and consistent dose delivery due to non-axial forces affecting the movement of the plunger, leading to misalignment and increased load on the pump motor, which results in dose inaccuracies.
Innovation Solution
A fluid delivery device with a syringe barrel and a plunger coupled via a pusher driven by an extending mechanism, utilizing telescopic nested screws and a mechanical ball joint configuration to minimize non-axial forces, ensuring precise axial motion and reducing wobble.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed coupling between pusher and plunger is used, then force transmission is efficient, but non-axial forces cause plunger misalignment and increased motor load
Solution Approach 1:
The patent employs a ball joint coupling mechanism where a spherical element on the pusher interfaces with a spherical recess on the plunger. This curved spherical geometry allows the coupling to accommodate non-axial forces and plunger misalignment without transmitting harmful loads, while still maintaining effective force transmission along the axial direction for accurate dose delivery.
2Manufacturing precision
If telescopic nested screws are used for the extending mechanism, then precise axial motion is achieved, but device complexity increases
Solution Approach 1:
The patent utilizes telescopic nested screws where multiple screw elements are arranged concentrically, with each screw nested within the previous one. This nesting arrangement allows precise axial motion control through differential rotation of the nested screws while minimizing the overall radial space required, thereby reducing device complexity compared to using larger, non-nested screw mechanisms.
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 enhances dose accuracy and stability of the plunger, maintaining high precision throughout the life cycle of the device without increasing cost or complexity, effectively addressing the issue of non-axial forces and improving the reliability of infusion devices.
Implementation Method 1
The extending mechanism comprises telescopic nested screws rotated controllably to extend and retract the pusher
Implementation Method 2
The protrusion and the recess can be configured to cooperate together as a mechanical ball joint to reduce tilt of the plunger
Data Source
AI summary
A fluid delivery device has a syringe barrel with reservoir chamber for fluid, a plunger that translates along a longitudinal axis to expel fluid, and a pusher dimensioned to translate within the barrel and coupled to a drive mechanism to controllably contact and move the plunger. The pusher contacts the plunger at its mechanical center to reduce tilt in the plunger. Contact faces of the pusher and plunger cooperate as a ball joint to minimize non-axial forces on the plunger face. The pusher can have a protrusion of various lengths extending toward and being at least partially received in a recess of various depths in the plunger. The pusher is rigidly connected to a drive mechanism for anti-rotation. The pusher can have scalloped edges for air venting, and apertures for cooperating with protrusions on the drive mechanism to prevent bottoming out the plunger when filling.