Rotating Screw Dosage System for Multi-Dose Injector
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Solution Overview
Problem
Current drug administration devices require frequent refilling and are not easily usable for self-administration of medicaments like hormone therapies, which necessitate regular injections over extended periods.
Innovation Solution
A disposable injection device with a dispensing mechanism featuring a plunger rod, user-operable push button, twist driver, and anti-reverse mechanism, allowing for repeated doses without refilling, designed for easy self-administration of medicaments like parathyroid hormone (teriparatide).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a device allows repeated administration of multiple doses without refilling, then the duration of action and productivity are improved, but the device complexity increases
Solution Approach 1:
The device is divided into distinct functional modules: a cartridge containing multiple doses of medicament, a plunger rod with screw thread for dose control, a twist driver mechanism for actuation, and a housing with ratchet mechanism. Each segment performs a specific function, allowing the system to deliver multiple doses while maintaining manageable complexity through modular design.
Solution Approach 2:
The plunger rod is nested within the cartridge, which is itself contained within the housing. The twist driver is nested within the push button assembly. This nested arrangement allows multiple components to occupy compact spaces without interfering with each other, enabling multi-dose functionality while controlling overall device size and complexity.
2Ease of operation
If a device is designed for easy self-administration, then the ease of operation is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The device incorporates a self-regulating mechanism where the screw thread on the plunger rod automatically controls the advancement distance with each rotation, ensuring precise dosing without requiring user calculation or measurement. The ratchet mechanism automatically prevents backward movement, and the biasing member automatically resets the push button, making the device self-correcting and easy to use while maintaining precision through inherent mechanical design rather than complex controls.
Solution Approach 2:
The screw thread pitch is carefully selected to convert simple rotational motion into precise linear advancement of the plunger rod. By changing the thread pitch parameter, the device achieves accurate dose control through a simple twisting motion, balancing ease of operation with manufacturing precision requirements.
3Reliability
If an anti-reverse mechanism is implemented to restrict push button movement to one direction, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The entire injection device is designed as a disposable unit, eliminating the need for complex reversible mechanisms. The anti-reverse function is achieved through a simple ratchet mechanism with flexible column protrusions that engage with ratchet teeth, allowing the device to maintain reliability for its intended single-use lifecycle without requiring complex reset or bidirectional control systems.
Solution Approach 2:
The anti-reverse function is extracted as a separate mechanical feature (ratchet and flexible column protrusions) independent of the main dosing mechanism. This modular approach allows the reliability function to be implemented with minimal additional complexity, as the ratchet mechanism operates independently from the screw thread and plunger rod dosing system.
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
Enables self-administration of precise, repeated doses of medicaments over extended periods, reducing the need for frequent medical visits and ensuring consistent delivery of medications like teriparatide for conditions such as osteoporosis.
Implementation Method 1
a plunger rod having a screw thread and configured to advance along the proximal-distal axis relative to the housing
Implementation Method 2
a user-operable push button moveable along the proximal-distal axis relative to the housing; a twist driver threadably engaged with the push button such that movement of the push button towards the distal end of the housing causes rotation of the twist driver about the proximal-distal axis
Implementation Method 3
a driver engaged with the twist driver such that rotation of the twist driver causes rotation of the driver, the driver also engaged with a portion of the plunger rod such that rotation of the driver causes rotation of the plunger rod, advancing the plunger rod along the proximal-distal axis
Implementation Method 4
an anti-reverse mechanism including: at least one ratchet integrally forming on an internal surface of the housing; and a flexible column integrally formed within a side opening of the push button, the flexible column having a flexible column protrusion at a proximal end thereof, wherein as the push button moves along the proximal-distal axis, the flexible column protrusion engages the ratchet and restricts movement of the push button to one direction
Data Source
AI summary
A dispensing mechanism for delivering a dosage of medicament including a housing having a proximal-distal axis; a plunger rod having a screw thread and configured to advance along the proximal-distal axis relative to the housing; a user-operable push button moveable along the proximal-distal axis relative to the housing; a twist driver threadably engaged with the push button such that movement of the push button towards the distal end of the housing causes rotation of the twist driver about the proximal-distal axis; and a driver engaged with the twist driver such that rotation of the twist driver causes rotation of the driver, the driver also engaged with a portion of the plunger rod such that rotation of the driver causes rotation of the plunger rod, advancing the plunger rod along the proximal-distal axis relative to the housing.