Starter Pulley Assembly with Overlapping Spring Receptacle
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Solution Overview
Problem
Existing pulley assemblies for starting internal combustion engines in hand-guided power tools are not compact enough, leading to space inefficiencies and potential cooling issues, as well as instability in the connecting spring which can result in spring breakage.
Innovation Solution
The pulley assembly features a spring receptacle and circumferential recess that overlap in both axial and radial directions, allowing for a compact design with a narrower first end of the connecting spring and a larger spring chamber, enabling efficient torque transmission and improved cooling air supply by reducing the pulley diameter and incorporating an air guiding contour.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the spring receptacle and circumferential recess are arranged separately in conventional designs, then each component has sufficient space, but the overall pulley assembly becomes larger and less compact
Solution Approach 1:
The spring receptacle and circumferential recess are merged into overlapping regions in both axial and radial directions, creating a compact integrated structure that reduces overall pulley assembly volume while maintaining functional integrity of both components
Solution Approach 2:
The spring receptacle is nested within the pulley structure such that its radial extent is contained within the pulley's radial boundaries, allowing the recess to extend outwardly while both components occupy overlapping spatial regions, achieving compact integration
2Volume of moving object
If the pulley diameter is reduced for compact design, then space requirements are minimized, but the torque transmission capability and spring stability may be compromised
Solution Approach 1:
The connecting spring is designed with non-uniform width, being narrower at its first end (where it connects to the pulley) and wider at its second end, optimizing the local structural properties to maintain torque transmission capability while reducing overall space requirements
Solution Approach 2:
The spring receptacle and recess overlap in both axial and radial directions, utilizing multiple spatial dimensions to achieve compact integration without compromising the functional performance of torque transmission
3Temperature
If the pulley assembly is made more compact in radial direction, then cooling air supply is improved, but the space for accommodating starter rope and spring may be reduced
Solution Approach 1:
The connecting spring is designed with variable width along its length, allowing it to accommodate the necessary rope volume while maintaining a compact radial profile that improves cooling air supply to the internal combustion engine
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 configuration results in a more compact and stable pulley assembly that reduces space requirements, enhances cooling efficiency, and minimizes the risk of spring breakage while maintaining sufficient stability and torque transmission.
Implementation Method 1
The pulley is connected to a damping spring by means of which the rotation energy of the pulley is transmitted to the crankshaft of an internal combustion engine
Data Source
AI summary
A pulley assembly for a starter device for starting an internal combustion engine of a hand-guided power tool has a pulley with an axis of rotation extending in axial direction. A circumferential side of the pulley is positioned outwardly in radial direction relative to the axis of rotation. A circumferential recess is arranged at the circumferential side and accommodates a starter rope. The pulley is provided with a spring receptacle. A connecting spring is disposed in the spring receptacle and has a first end fixedly connected to the pulley. The spring receptacle and the recess overlap each other, viewed in the axial direction and viewed in the radial direction. A starter device is provided with the pulley assembly and a second end of the connecting spring is fixedly connected to a coupling device of the starter device that couples the pulley to the crankshaft of the combustion engine.