Auto-injector Dual Screw Thread Mechanism for Speed Force Trade-off
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing auto-injectors face challenges in providing the necessary varying speeds and forces for needle insertion and medicament delivery, often requiring multiple motors, which makes them cumbersome, prone to breakage, and increases weight and manufacturing costs.
Innovation Solution
An auto-injector design featuring a single motor with a dual screw thread arrangement, where the first screw thread provides rapid, low-force insertion and the second screw thread provides slow, high-force delivery, allowing for modulation of speed and torque through differing thread pitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If multiple motors are used to provide different driving forces and speeds for insertion and delivery phases, then the force and speed requirements are met, but the device becomes heavy and cumbersome
Solution Approach 1:
The patent combines the functions of multiple motors into a single motor by using a multi-start screw thread mechanism. The single motor drives a plunger that engages with different screw threads (first screw thread for insertion, second screw thread for delivery) to provide the required varying forces and speeds without the weight and complexity of multiple motors
Solution Approach 2:
The patent changes the mechanical parameters (thread pitch and lead) of the screw thread arrangement to provide different driving characteristics. The first screw thread has a first pitch for rapid low-force insertion, while the second screw thread has a second pitch for slow high-force delivery, allowing a single motor to adapt its output characteristics through the mechanical transmission system
2Force
If multiple motors are used to provide different driving forces and speeds, then the force and speed requirements are met, but the device complexity increases
Solution Approach 1:
The patent merges multiple motor functions into a single motor-screw thread system. The multi-start screw thread arrangement with different pitches allows one motor to perform the work of multiple motors by mechanically transforming the rotation into different linear motion characteristics for different phases of operation
Solution Approach 2:
The single motor and screw thread arrangement serve multiple functions: the first screw thread arrangement provides rapid insertion motion, while the second screw thread arrangement provides slow delivery motion. This multi-functional design eliminates the need for separate motors for each function, reducing overall device complexity
3Device complexity
If a single motor is used to drive the plunger, then the device weight and complexity are reduced, but it becomes difficult to provide both rapid low-force insertion and slow high-force delivery
Solution Approach 1:
The patent uses parameter changes in the screw thread geometry to enable speed and force modulation. By providing a first screw thread with a first pitch for rapid motion and a second screw thread with a second pitch for slow motion, the system allows a single motor to adapt its output characteristics through the mechanical transmission system
Solution Approach 2:
The patent introduces dynamic characteristics through the multi-start screw thread mechanism. The plunger can engage with different screw threads depending on the operational phase, allowing the system to dynamically adjust its mechanical advantage and motion characteristics without changing the motor itself
4Speed
If rapid insertion is provided, then the insertion speed is improved, but the insertion force becomes too low for effective medicament delivery
Solution Approach 1:
The patent applies parameter changes by using different screw thread pitches for different phases. The first screw thread has a larger pitch for rapid insertion with lower force, while the second screw thread has a smaller pitch for slow delivery with higher force, allowing the system to optimize speed and force for each specific task
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
This design enables efficient and comfortable needle insertion and effective medicament delivery with reduced weight, cost, and complexity, while ensuring safe and reliable operation.
Implementation Method 1
The first screw thread arrangement is configured to, during an insertion phase, cause axial movement of the plunger upon rotation of the plunger by the drive means
Implementation Method 2
The second screw thread arrangement is configured to, during a delivery phase subsequent to said insertion phase, cause axial movement of the plunger upon rotation of the plunger by the drive means
Implementation Method 3
A thread pitch of the first screw thread arrangement is different from a thread pitch of the second screw thread arrangement. The first speed may be greater than the second speed. The first torque may be lesser than the second torque. The differing speeds and torques may be provided by the differing thread pitch
Data Source
AI summary
According to an aspect of the present invention there is provided an auto-injector. The auto-injector includes a housing configured to receive or couple to a syringe; a plunger disposed within the housing; a drive means configured to rotate the plunger; a first screw thread arrangement configured to, during an insertion phase, cause axial movement of the plunger upon rotation of the plunger by the drive means; and a second screw thread arrangement configured to, during a delivery phase subsequent to said insertion phase, cause axial movement of the plunger upon rotation of the plunger by the drive means, wherein a thread pitch of the first screw thread arrangement is different from a thread pitch of the second screw thread arrangement.