Hospital Bed Siderail Linkage for Deck Height and Floor Clearance
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Solution Overview
Problem
Designing a siderail assembly for hospital beds that meets the requirements of minimum deck height, floor clearance, and rail orientation while accommodating both step and flat decks is challenging due to conflicting mechanical constraints and the need for a cost-effective mechanism.
Innovation Solution
A siderail assembly with a specific linkage mechanism involving pivotally connected links P, R, and Q, where the common ends of links Q and R are pivotably connected at joint A, constrained to move parallel to a reaction surface, allowing for vertical adjustment and achieving a bottom-in/top-out orientation, suitable for both step and flat decks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the rail offset distance is reduced to achieve lower minimum deck height, then the deck height requirement is improved, but the floor clearance requirement deteriorates
Solution Approach 1:
The patent applies a dynamic linkage mechanism where the rail can change its lateral position relative to the mattress dynamically. The linkage allows the rail to move between a first lateral position (closer to mattress) and a second lateral position (farther from mattress), enabling the system to adapt the offset distance based on operational requirements. This dynamic adjustment resolves the contradiction by allowing minimal offset for low deck height when needed, while providing sufficient offset to maintain floor clearance when the rail is in the raised position.
2Length of stationary object
If the rail is positioned closer to the mattress (reduced offset distance), then the minimum deck height can be reduced, but the occupant stability deteriorates due to increased distance from center of gravity
Solution Approach 1:
The linkage mechanism enables the rail to dynamically adjust its lateral position. When the rail is in the raised position, it can be positioned farther from the mattress to provide occupants with better stability and closer proximity to their center of gravity. When the rail is in the lowered position, it can be positioned closer to the mattress to minimize the deck height requirement. This dynamic repositioning resolves the contradiction between deck height minimization and occupant stability.
3Device complexity
If a conventional drop down mechanism is used, then the rail remains upright which simplifies the mechanism, but the rail cannot achieve bottom-in/top-out orientation needed for improved occupant stability
Solution Approach 1:
The patent employs a dynamic linkage mechanism that goes beyond the conventional drop down design. The linkage connects the rail to the elevatable frame through multiple links (first link, second link, third link) with specific geometric relationships that enable the rail to rotate and change orientation. This allows the rail to achieve a bottom-in/top-out orientation when needed, improving occupant stability while maintaining reasonable mechanism complexity through the use of standard linkage components.
Data Source
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AI summary
A siderail assembly 40 for a bed 20 includes a link P pivotably connectable to a bed frame at a joint PF and to a rail at a joint PR The link P has at least one reaction surface 64, 66. The assembly also includes a link R having a rail end 78 and a common end 80. The rail end of link R is pivotably connected to the rail at a joint RR. The assembly also includes a link Q having a frame end 72 and a common end 74. The frame end of link Q is pivotably connected to the frame at a joint QF. The common ends of link Q and link R are pivotably connected to each other at a joint A constrained to move substantially parallel to the reaction surface.