Self-Locking Mechanism Using Four-Bar Linkage for Lift Chair Safety
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Solution Overview
Problem
Conventional lift chair metal frames lack a reliable self-locking mechanism, leading to safety issues when the supporting member is subjected to upward external forces during transitions between stances, such as from the footrest or reclined positions, as the existing position limiting pin system fails to maintain control over the supporting member's movement.
Innovation Solution
A self-locking mechanism incorporating a four-bar linkage mechanism with a locking rod and guide slot, which rotates between locking and unlocking positions to prevent the supporting member from moving upward, utilizing rivets and a position limiting pin to maintain stability across various stances, and includes a spring for additional downward force when unlocking to prevent upward movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional position limiting pin system is used to restrict supporting member movement, then the structure is simple, but the supporting member cannot be reliably prevented from moving upward under external forces during stance transitions
Solution Approach 1:
The locking rod is designed to dynamically rotate between locked and unlocked positions based on the supporting member's movement state. The guide slot in the rear rotating member allows the locking rod to automatically transition between engagement and disengagement states, providing adaptive locking control that responds to external forces and position changes without requiring complex control systems
Solution Approach 2:
The self-locking mechanism is segmented into distinct functional components: the locking rod for primary locking, the guide slot for controlled movement, and the spring for auxiliary locking force. This segmentation allows each component to perform its specific function efficiently while maintaining overall system reliability without excessive complexity
2Ease of operation
If the supporting member is allowed to move freely between positions, then the ease of operation is improved, but safety issues arise when upward external forces are applied during transitions
Solution Approach 1:
The locking rod is positioned and oriented to preemptively counteract upward external forces before they can cause hazardous movement. The guide slot is designed to guide the locking rod into the locked position in advance, creating a preventive barrier against upward movement hazards during stance transitions
Solution Approach 2:
The guide slot acts as an intermediary element between the locking rod and the rear rotating member, mediating the interaction between these components. It controls the locking rod's movement path and ensures proper engagement while allowing smooth transitions, thus facilitating ease of operation without compromising safety
3Object-affected harmful factors
If a locking mechanism is added to prevent upward movement of the supporting member, then safety is improved, but the device complexity increases
Solution Approach 1:
The self-locking mechanism is merged with the existing bar linkage mechanism of the lift chair. The locking rod, rear rotating member, and guide slot are integrated into the supporting member's movement system, allowing the locking function to be achieved without adding a separate, independent locking system that would increase complexity
4Ease of operation
If the locking rod is held in the unlocked position to allow free movement, then the ease of operation is improved, but the supporting member may move upward uncontrollably
Solution Approach 1:
The spring provides self-service by automatically generating locking force without requiring external power or control. The spring's elastic force continuously pushes the locking rod toward the locked position, creating a passive safety mechanism that maintains position control reliability while allowing controlled mobility when needed
Data Source
AI summary
A self-locking mechanism includes a frame (1), a transmission member (3), a rotating member (2), and a locking rod (4), forming a four-bar linkage mechanism. A supporting member (6) is movable relative to the frame (1). The rotating member (2) has an upper end rotatably connected with the supporting member (6), a lower end provided with a guide slot (22), and a middle portion therebetween. The transmission member (3) has two ends rotatably connected with the frame (1) and the middle portion respectively. The locking rod (4) has an upper end rotatably connected with the frame (1), and a lower end provided with a guide rod (41) movable in the guide slot. The locking rod (4) is rotatable between multiple positions. When the locking rod (4) is in a locking position, the guide rod (41) abuts against the guide slot to prevent the supporting member (6) from moving upward.