Torsion Spring Automatic Assembly in Injection Devices
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Solution Overview
Problem
The manual assembly of torsion springs in injection devices is labor-intensive and not cost-effective for large-scale production, and existing automatic assembly methods are inadequate for achieving correct alignment and securing of the springs.
Innovation Solution
A method and design for automatically anchoring a torsion drive spring to a housing in injection devices using complementary formations on the spring and housing, allowing for secure engagement through rotation, which includes features like collar elements, hooked portions, and resiliently deformable parts for easy assembly by automated machines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manual assembly methods are used to attach torsion springs to housing, then alignment precision and assembly correctness are improved, but labor costs and assembly time increase
Solution Approach 1:
The torsion spring assembly features self-aligning complementary formations (protrusions and recesses) that automatically guide the spring into correct orientation during automatic assembly, eliminating the need for skilled manual alignment while enabling rapid machine-based installation
Solution Approach 2:
A collar element serves as an intermediary component between the torsion spring and housing, providing complementary formations that facilitate automatic alignment and securing of the spring during machine-based assembly operations
2Productivity
If automatic assembly methods are used to attach torsion springs to housing, then productivity and cost-effectiveness are improved, but assembly precision and reliability deteriorate
Solution Approach 1:
The complementary formations on the torsion spring and housing are designed with asymmetric geometries (specific angular orientations of protrusions and recesses) that enable automatic self-alignment during machine assembly, ensuring precise spring positioning without requiring manual intervention while maintaining high assembly speeds
3Measurement precision
If complex spiral or threaded scales are used on the drive shaft, then precise dose setting is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The dose setting function is segmented from the drive shaft scale, allowing the drive shaft to rotate freely beyond 360 degrees while dose measurement is handled by a separate ratcheted dose setting knob with angular markings, simplifying the drive shaft design and enabling multi-rotation operation
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 rapid and accurate automatic assembly of injection devices, reducing labor costs and ensuring proper alignment of springs, while allowing for dose setting knob rotation beyond 360° without complex scales, enhancing production efficiency.
Implementation Method 1
a torsion drive spring anchored at one end region relative to said drive shaft and at its other end region being secured to a fitting adapted to non-rotatably engage a seat on said housing
Implementation Method 2
a spring-driven rotary drive shaft which during a dose setting routine is rotated against the force of the spring in a first sense from a rest position to a preset angular position
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3(a)~3(f)
AI summary
An injection device includes a housing (40) for containing a syringe or cartridge (14) of medicament; a rotary drive shaft (20) for being rotated by an adjustable preset amount to cause expression of a corresponding amount of medicament from the syringe or cartridge; a torsion drive spring (24) anchored at one end region relative to the drive shaft (20) and, at its other end region being secured to a fitting (44) adapted to non-rotatably engage a seat (48, 50) on the housing.