Dispensing Device Cam Drum Linear Helical Profiles
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Solution Overview
Problem
Existing injector pens for delivering fixed doses of medication are costly, complex, and inefficient, with mechanisms that prevent re-use after the end of life, lacking cost-effectiveness and accuracy in dose setting and delivery.
Innovation Solution
A dispensing device featuring a thumb pad and cam drum with linear and helical cam profiles, one-way ratchets, and EOL locks, allowing for precise dose setting and delivery while preventing re-use after the final dose is delivered, using a combination of linear and helical cam profiles to convert linear motion into circular motion for consistent dose delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex mechanisms are used to deliver fixed doses and prevent re-use, then dose accuracy and safety are improved, but device complexity and cost increase
Solution Approach 1:
The device is divided into distinct functional modules: a cartridge for medication storage, a cam drum with linear and helical profiles for dose control, a thumb pad for actuation, and EOL locks for safety. Each module performs a specific function, allowing the complex dose delivery mechanism to be broken down into manageable, independently optimized components that reduce overall system complexity while maintaining precision.
Solution Approach 2:
The cam drum profiles are designed to automatically control the plunger movement through the interaction of the thumb pad with the linear and helical cam surfaces. The mechanism self-regulates the dose delivery process without requiring additional electronic sensors or complex control systems, achieving precise dose measurement through purely mechanical means.
2Reliability
If mechanisms are added to prevent re-use after end of life, then patient safety is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
EOL lock features are pre-integrated into the cam drum and cartridge assembly during manufacturing. The linear cam profile includes predetermined EOL lock engagement surfaces that automatically activate when the plunger reaches the end of its travel, preventing any subsequent re-use without requiring additional manufacturing steps or assembly operations.
Solution Approach 2:
The EOL lock mechanism is merged with the existing cam drum structure rather than being added as a separate component. The linear cam profile serves dual purposes: controlling plunger movement during dose delivery and enabling EOL locking after the final dose, thereby preventing re-use while avoiding additional manufacturing complexity.
3Productivity
If linear and helical cam profiles are used to convert linear motion to circular motion, then dose delivery consistency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The cam drum incorporates both linear and helical cam profiles that convert the linear back-and-forth motion of the thumb pad into controlled rotational movement of the plunger. The helical profile specifically transforms linear displacement into precise angular rotation, ensuring consistent dose delivery through geometric design rather than requiring high-precision manufacturing tolerances.
Solution Approach 2:
The cam profiles are designed with specific geometric parameters (pitch, angle, curvature) that determine the relationship between thumb pad displacement and plunger movement. By carefully selecting these parameters, the mechanism achieves consistent dose delivery through the mathematical relationship between linear and rotational motion, reducing the need for extreme manufacturing precision.
4Reliability
If EOL locks are integrated into the cam drum, then prevention of re-use is improved, but device complexity increases
Solution Approach 1:
The linear cam profile on the cam drum serves multiple functions: controlling plunger movement during dose delivery, enabling EOL lock engagement after the final dose, and preventing any subsequent re-use attempts. This multi-functionality eliminates the need for separate EOL lock mechanisms, reducing overall device complexity while maintaining reliable prevention of re-use.
Solution Approach 2:
The EOL lock features are pre-configured into the cam drum structure during manufacturing. When the plunger reaches the end of its travel after the final dose, the linear cam profile automatically positions the EOL lock features to prevent any further actuation, without requiring additional sensors, actuators, or control systems.
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 dispensing device ensures accurate and efficient delivery of a fixed dose with each actuation, preventing re-use after the end of life, thereby improving cost-effectiveness and user safety by integrating complex mechanisms into a simpler, more efficient design.
Implementation Method 1
The cam drum includes at least one linear cam profile and at least one helical cam profile that are disposed on a surface on the cam drum. The thumb pad is configured to ride on the least one linear cam profile when setting the dose and is further configured to ride on the at least one helical cam profile when delivering the dose.
Data Source
AI summary
A dispensing device is provided to dispense a designated amount of a material on every dose delivery operation. The dispensing device includes a thumb pad, a cam drum coupled to the thumb pad, and a pawl nut comprising a one-way pawl. The thumb pad may be pulled out in a direction away from a distal end of the dispensing device for setting a dose of the material to be dispensed out and may be pushed in towards the distal end for delivering the dose. The cam drum includes a plurality of linear cam profiles and a plurality of helical cam profiles that may be disposed on a surface of the cam drum. The one-way pawl may engage with a ratchet disposed at a distal end of the cam drum and may prevent a rotation of the cam drum in an undesired direction.