Ultra-Low Patient Bed Caster Linkage for Mobility at Any Height
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Solution Overview
Problem
Ultra-low patient beds lack mobility in all height positions due to non-vertical caster stems, which restricts movement, and existing solutions either increase cost, width, or require electrical power, making them impractical for continuous use in hospitals and long-term care facilities.
Innovation Solution
The design incorporates a caster support member that remains vertically oriented through a constraint mechanism, such as a control arm or planetary gear arrangement, and a central actuation mechanism for selective locking of caster assemblies, allowing the bed to be steerable in all height positions without increasing width or requiring electrical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the bed is designed to achieve ultra-low lowermost height position by eliminating the lower secondary frame and pivotally attaching legs to the frame, then the bed height is reduced to minimize patient injury risk, but the caster stem becomes non-vertical at all but one height position, preventing the bed from being mobile in all height positions
Solution Approach 1:
The caster support member is designed to dynamically pivot relative to the leg, allowing the caster stem to maintain vertical orientation despite changes in bed height. This dynamic adjustment enables the caster wheel to track the direction of movement of the bed at any height position, resolving the contradiction between ultra-low height and continuous mobility.
Solution Approach 2:
The casting assembly is separated into distinct components: the caster support member attached to the leg, the caster stem, and the caster wheel. This segmentation allows independent movement of each component, enabling the support member to pivot while the stem remains vertical, thus maintaining mobility across all height positions while achieving ultra-low bed height.
2Reliability
If two caster assemblies are provided on either side of the pivotal attachment as disclosed in Megown, then the caster support assembly remains in position as the leg angularly moves, maintaining verticality of the caster stem, but the cost increases and the bed becomes more difficult to maneuver
Solution Approach 1:
The single caster support member performs multiple functions: it supports the caster assembly, allows vertical movement of the leg, and pivots to maintain caster stem verticality. This multi-functional design eliminates the need for separate caster assemblies on either side, reducing complexity while maintaining reliability.
Solution Approach 2:
The invention extracts the verticality-maintaining function from the caster assembly configuration itself and implements it through the pivotal attachment of the caster support member to the leg. This eliminates the need for the complex two-caster-assembly configuration described in Megown, reducing device complexity while preserving the verticality of the caster stem.
3Reliability
If the caster support member is offset along the width of the bed as disclosed in Schell, then the caster assemblies do not interfere with the frame when the bed is lowered, but the width of the bed increases, causing problems when negotiating openings such as doorways
Solution Approach 1:
The caster support member is designed to pivot dynamically as the bed height changes, allowing it to move from a position that could interfere with the frame at low heights to a retracted position at higher heights. This dynamic movement eliminates the need for permanent offset, maintaining non-interference reliability without increasing bed width.
Solution Approach 2:
Instead of offsetting the caster support member along the width of the bed (horizontal dimension), the invention allows it to move in the vertical dimension through pivotal attachment. This dimensional change enables the support member to clear the frame at low heights without increasing bed width, thus avoiding doorway negotiation problems.
4Ease of operation
If a central actuation mechanism is provided for selective locking of caster assemblies, then the bed becomes easier to maneuver by preventing swiveling of caster assemblies, but the device complexity increases
Solution Approach 1:
The caster assembly includes a self-contained locking mechanism that can be actuated by the user without requiring a complex central actuation system. The simple lockable caster assembly design allows users to manually lock or unlock the caster, providing ease of maneuverability when needed while avoiding the complexity of centralized actuation mechanisms.
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
The solution enables the bed to maintain vertical caster stem orientation and selective locking, ensuring mobility and ease of maneuverability in all positions, reducing the risk of patient injury and operational complexity while maintaining cost-effectiveness.
Implementation Method 1
a constraint means attached to the caster support member, the constraint means urging the caster support member to pivot in a second direction opposite the first direction when the frame is lowered to thereby maintain the vertical orientation of the caster stem
Implementation Method 2
constraint mechanism, such as a control arm or planetary gear arrangement
Implementation Method 3
The caster wheel swivels about the stem when the bed is propelled along the floor so that the caster wheel tracks the direction of movement of the bed
Data Source
AI summary
A steerable ultra-low patient bed that incorporates a means for maintaining verticality of the caster stem at all height positions of the bed and a means for selectively locking the caster assemblies of the bed in a desired locking position. The means for selectively locking the caster assemblies may be actuated from either end of the bed using a central actuation mechanism. The bed according to the present invention has legs that are pivotally and translatably attached at their upper end to a frame of the bed and caster support members that are longitudinally aligned with the bed pivotally attached to the lower end of each leg. The caster support members each have a single caster assembly attached thereto. The means for maintaining verticality of the caster stem incorporates a constraint means that urges the caster support member in a direction of rotation opposite to that of the leg during adjustment of the height of the bed.