Recoil Starter Coil Spring Protection via Local Quality
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Solution Overview
Problem
Existing recoil starters with integrated or elastically connected rope reels and cams face issues with coil spring deformation due to clearance between the extending cylindrical portion and the seat face, leading to increased stress and reduced durability, especially when space constraints require a smaller overall height.
Innovation Solution
A recoil starter design featuring a rope reel, cylindrical cam, coil spring, and specific annular portions to prevent coil spring entry into clearance, with a U-shaped hook engaging a T-letter shaped groove, and outer annular portions configured to maintain stability and prevent deformation, allowing the coil spring to be wound without increasing the overall height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a clearance is left between the leading end of the extending cylindrical portion and the seat face of the rope reel, then the cylindrical cam rotates more smoothly, but the coil spring may enter the clearance when wound and fastened, causing deformation and reduced durability
Solution Approach 1:
The recess is designed with differentiated local qualities: the inner annular portion maintains a specific height to allow smooth rotation, while the outer annular portion is formed to have a larger height than the inner annular portion, creating a localized barrier that prevents coil spring entry into the clearance area
2Volume of moving object
If the coil spring is wound and fastened tightly to reduce diameter, then it comes closer to the extending cylindrical portion, but the wire may repeatedly enter the clearance, deforming the spring and increasing stress
Solution Approach 1:
The outer annular portion is formed to have a larger height than the inner annular portion, creating a localized protective barrier specifically where the coil spring is most likely to enter the clearance during winding and fastening operations
3Length of stationary object
If the overall height is reduced to save space, then the device becomes more compact, but the receiving groove structure cannot be adopted, making it difficult to prevent coil spring entry
Solution Approach 1:
Instead of requiring a full receiving groove that increases overall height, the invention creates a localized protective structure by forming the outer annular portion with a larger height than the inner annular portion, providing targeted protection against coil spring entry without compromising compactness
Solution Approach 2:
The solution moves from a vertical receiving groove approach to a differential height approach in the radial dimension, where the outer annular portion extends higher than the inner annular portion to create a protective barrier that prevents coil spring entry into the clearance
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 design effectively prevents coil spring deformation and stress, maintaining durability while allowing the recoil starter to operate within a smaller overall height, ensuring reliable engine starting without compromising the structural integrity of the coil spring.
Implementation Method 1
a coil spring (6) for connecting the rope reel (3) and the cylindrical cam (4)
Implementation Method 2
a centrifugal ratchet (29) to be brought into and out of engagement with that cam
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A recoil starter includes: a rope reel; a cylindrical cam; a coil spring; a reel spindle; an extending cylindrical portion; a recess; a hook; an engaging groove; an inner annular portion; and an outer annular portion, wherein: the extending cylindrical portion is inserted in the inner side of the recess; the coil spring is wound on the outer side of the extending cylindrical portion; the hook is engaged with the engaging groove; an end portion opposite the hook of the coil spring is engaged with the cylindrical cam; the inner annular portion is made flush; and the outer annular portion is made such that a portion corresponding to the engaging groove is formed to have the same height as that of the inner annular portion whereas an opposite side is formed to have a larger height than that of the inner annular portion.