Angled Wrap Spring Installation to Prevent Sleeve Jamming
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Solution Overview
Problem
Wrap springs often get stuck during installation due to excessive friction when threaded over a sleeve, leading to failed installations and potential robot arm shutdowns, especially when trying to establish a frictional engagement between engine shafts and belt pulleys in motor vehicles.
Innovation Solution
The wrap spring is applied at an angle to a sleeve, allowing elastic twisting to reduce its nominal diameter and minimize frictional contact, enabling easier threading and distribution of tension without jamming, and can be automated using robot arms to avoid unnecessary resistance forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the wrap spring is applied coaxially to the sleeve and threaded over a funnel-shaped insertion bevel, then the installation process is straightforward, but the wrap spring gets stuck due to excessive friction during threading
Solution Approach 1:
The wrap spring is applied at an angle (inclined alignment) rather than coaxially to the sleeve's longitudinal axis. This angular application creates a more tangential contact region on the lateral surface, reducing the frictional surface area and minimizing the friction torque that opposes tensioning during installation, thereby preventing the wrap spring from getting stuck
2Reliability
If the wrap spring is tensioned to establish frictional engagement, then the frictional contact is improved, but the wrap spring jams during threading due to excessive friction
Solution Approach 1:
The wrap spring is pre-twisted in or against the winding direction before installation to reduce its nominal diameter. This preliminary action allows the wrap spring to be threaded onto the sleeve more easily, and the frictional engagement is established after threading is complete, avoiding the jamming problem that occurs when tensioning is applied during threading
Solution Approach 2:
By applying the wrap spring at an angle rather than coaxially, the frictional contact occurs over a more tangential partial region rather than the entire circumference. This dimensional change in contact geometry reduces the frictional surface area and minimizes the friction torque that would otherwise oppose tensioning and cause jamming
3Productivity
If automated installation with robot arms is used, then productivity is improved, but sudden resistance forces cause unscheduled shutdowns
Solution Approach 1:
The inclined alignment of the wrap spring at an angle to the sleeve's longitudinal axis reduces the frictional surface area and minimizes the friction torque during installation. This eliminates sudden resistance forces that would exceed the force applied by robot arm motors, preventing unscheduled shutdowns and enabling reliable automated installation
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 method reduces the risk of wrap spring jamming during installation, allowing for simple and automated installation of wrap spring clutches by minimizing frictional resistance and ensuring smooth tensioning, even with robot-assisted processes.
Implementation Method 1
the wrap spring is elastically twisted to change the nominal diameter thereof. While the wrap spring contacts the lateral surface of the first sleeve, a resulting angle between the first longitudinal axis of the first sleeve and a central axis of the wrap spring is reduced
Data Source
AI summary
A method for installing a wrap spring includes providing a first sleeve with a first longitudinal axis extending in an axial direction and a lateral surface, and the wrap spring designed to frictionally abut the lateral surface. The wrap spring includes a nominal diameter and a central axis. The method includes applying the wrap spring in a relaxed state to the lateral surface at an angle α between the central axis and the first longitudinal axis, elastically twisting the wrap spring to change the nominal diameter while the wrap spring contacts the lateral surface, reducing the angle α, threading the wrap spring onto the first sleeve, and relaxing the wrap spring to establish frictional contact with the lateral surface.