Dual-Locking Castor Brake for Slip-Free Chair Positioning
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Solution Overview
Problem
Conventional chair castors experience slipping due to the castor body rotating relative to the fixing bolt when the rollers are locked, leading to instability and inconvenience.
Innovation Solution
A castor design where the brake unit's drive member, when pressed, simultaneously locks the rollers onto the castor body and the castor body onto the fixing bolt, preventing rotation and enhancing the locking effect by using a positioning block and locking pin mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the braking member is movable into the locking grooves to lock the rollers onto the castor body, then the wheel unit is locked, but the castor body can still rotate relative to the fixing bolt causing slipping
Solution Approach 1:
The patent combines two locking functions into a single brake unit operation: the braking member locks the rollers onto the castor body while the positioning block simultaneously locks the castor body onto the fixing bolt. This merging of functions ensures that when the brake is applied, both the wheel unit and the castor body are locked simultaneously, preventing slipping while maintaining ease of operation through a single actuation.
Solution Approach 2:
The positioning block acts as an intermediary element between the brake unit and the fixing bolt. When the braking member engages the locking grooves, the positioning block is simultaneously engaged with the locking holes on the fixing bolt, mediating the transfer of locking force and ensuring the castor body cannot rotate relative to the fixing bolt, thereby preventing slipping.
2Device complexity
If a simple brake unit is used to lock the rollers, then the device complexity is low, but the castor body rotates relative to the fixing bolt reducing stability
Solution Approach 1:
The brake unit is designed to merge two locking functions: the braking member for locking rollers and the positioning block for locking the castor body to the fixing bolt. This integration adds minimal complexity while significantly improving stability, as both locking actions occur simultaneously through a single brake actuation mechanism.
Solution Approach 2:
The brake unit serves multiple functions: it acts as both a braking mechanism for the rollers and a positioning mechanism for the castor body. The positioning block with locking holes provides multi-functionality by enabling the castor body to be locked onto the fixing bolt, thereby enhancing stability without requiring a separate positioning system.
3Ease of operation
If the castor body is allowed to rotate relative to the fixing bolt, then the ease of operation for positioning is improved, but the wheel unit slips when locked
Solution Approach 1:
The castor body is designed with dynamic positioning capability through multiple locking holes that can engage at different positions on the fixing bolt. This allows the castor body to be positioned at various angles during operation while maintaining stability when locked, as the positioning block can engage with any of the locking holes to prevent rotation after positioning is achieved.
Solution Approach 2:
The positioning block serves as an intermediary that enables both positioning flexibility and locking stability. During positioning, the castor body can rotate freely until the desired position is reached, then the positioning block engages with the appropriate locking hole on the fixing bolt to prevent further rotation, thereby maintaining both ease of positioning and locking stability.
Data Source
AI summary
A castor includes a suspension unit, a castor body, a wheel unit, and a brake unit. The suspension unit includes an upright fixing bolt and a locking member. The wheel unit includes two rollers. The brake unit includes a positioning block, a sliding block, a biasing member, a drive member, and a braking pin. Thus, when the drive member of the brake unit is pressed, each of the rollers of the wheel unit is braked by and locked onto the castor body, and the castor body is locked onto the fixing bolt simultaneously, thereby locking the castor exactly and stably.