Hoist Overload Prevention Using Coil Spring Drive
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Solution Overview
Problem
Existing overload preventing apparatuses for hoists face challenges such as reduced stroke and height of belleville springs leading to increased fabrication errors, instability, and difficulty in adjusting spring pressures, resulting in variations in slip load and friction issues, while also making the hoist larger in size.
Innovation Solution
An overload preventing apparatus with a drive member and a rotation drive member that utilizes a coil spring with a large stroke, where the spring is wound around the drive member and a spring holder is used to provide a uniform urging force, allowing for a larger height of engagement teeth and reduced fabrication errors, without increasing the hoist's size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If belleville spring stroke is reduced to downsize the hoist, then the hoist size is reduced, but the height of locking teeth must be reduced and machining accuracy increases cost
Solution Approach 1:
The patent changes the spring type from belleville spring to coil spring, fundamentally altering the stroke parameter characteristics. Coil springs provide large stroke with sufficient height, eliminating the need for precise machining of locking teeth while maintaining compact hoist dimensions through the spiral arrangement of the coil spring around the drive shaft.
Solution Approach 2:
The coil spring is arranged in a spiral shape around the outer periphery of the drive shaft, utilizing the circumferential dimension. This three-dimensional arrangement allows the spring to achieve large stroke without increasing the axial height, thereby avoiding the need for precise locking teeth height machining.
2Volume of moving object
If belleville spring stroke is reduced, then the hoist is compact, but fabrication tolerance errors increase and product quality stability deteriorates
Solution Approach 1:
By switching to coil springs with large stroke, the patent creates a system where the spring pressure is less sensitive to accumulated dimension errors. The larger stroke provides a buffer that reduces the impact of fabrication tolerances, thereby improving product quality stability without requiring excessive machining precision.
3Volume of moving object
If belleville spring stroke is reduced, then the hoist is compact, but spring pressure adjustment range becomes very small and adjustment becomes difficult
Solution Approach 1:
The coil spring design with large stroke provides a broader adjustment range for spring pressure. The extended stroke allows for more significant variations in compression, enabling easier and more effective adjustment of the overload prevention threshold without being constrained by a narrow adjustment window.
4Length of moving object
If multiple belleville springs are laminated to achieve large stroke, then the stroke is increased, but the hoist becomes large-sized
Solution Approach 1:
Instead of laminating multiple springs axially to increase stroke, the patent uses a single coil spring arranged in a spiral around the drive shaft. This utilizes the circumferential space to achieve large stroke without increasing the axial dimension, thereby maintaining compact hoist size while providing the necessary spring travel for reliable overload prevention.
Solution Approach 2:
The patent combines the functions of multiple laminated springs into a single coil spring structure. The spiral arrangement allows one spring to provide the cumulative stroke effect that would otherwise require multiple stacked springs, reducing the overall volume and simplifying the structure.
5Device complexity
If hand wheel is guided by slight contact with drive member flange, then the structure is simple, but friction is brought about in sliding face during operation
Solution Approach 1:
The patent introduces a guide portion as an intermediary element between the hand wheel and drive member. This guide portion, formed as a groove on the drive member that receives the hand wheel's protrusion, provides smooth guidance while distributing the contact force, thereby reducing friction compared to direct flange contact.
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 solution provides a stable and accurate overload detection with reduced friction and variation in slip load, eliminating the need for multiple spring layers and adjustment, while maintaining a compact design.
Implementation Method 1
a spring member wound around an outer periphery of the drive member for pressing the rotation drive member to a side of the drive member
Data Source
AI summary
An overload preventing apparatus of a hoist characterized in including a drive shaft 2 for driving a load sheave 1, a pressure receiving member 4 outwardly fitted to the drive shaft 2, a drive member 10 for transmitting a drive force from operating means 14 to the drive shaft 2 by way of the pressure receiving member 4, a rotation drive member 12 including means of transmitting the drive force from the operating means 14 to the drive member 10 and releasing an engagement with the drive portion 10 when the operating means 14 is applied with a torque equal to or larger than a predetermined torque value and an elastic member 13 mounted along an axial direction of the drive member between a back face of the rotation drive member 12 and an inner side end face of the operating means 14 to pose a problem that a belleville spring is obliged to be used as urging means, and therefore, a stroke in the axial direction of the urging means is small, also a height of an engaging claw becomes small in accordance with the stroke of the belleville spring and a variation in a load relative to a height of the claw becomes large.