Dynamic Auxiliary Wheel Load Control for Hospital Bed Stability
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Solution Overview
Problem
Conventional patient transport apparatuses face challenges in maintaining stability and control during movement, particularly when navigating long hallways or corners, due to the non-swiveling auxiliary wheels, which can lead to teetering or slipping issues depending on the load distribution.
Innovation Solution
The patient transport apparatus incorporates an auxiliary wheel assembly with actuators that control the deployment of auxiliary wheels to adjust the normal force and frictional force, using a sensing system and controller to dynamically adjust the load carried by these wheels based on the patient's weight and movement conditions, ensuring stable and controlled movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the normal force on auxiliary wheels is increased to prevent slipping, then frictional force increases, but the patient transport apparatus may teeter-totter and caster wheels may lift off the ground
Solution Approach 1:
The patent makes the auxiliary wheels dynamically adjustable by deploying them only when needed for straight-line movement and retracting them when maneuvering is required. This dynamic deployment/retraction mechanism allows the system to adapt the normal force on auxiliary wheels based on operational requirements, preventing both slipping (when deployed) and teeter-tottering (when retracted), thus resolving the contradiction between grip reliability and apparatus stability.
2Stability of the object's composition
If the normal force on auxiliary wheels is decreased to maintain stability, then the apparatus remains stable, but the auxiliary wheels may slip on the floor surface during movement
Solution Approach 1:
The dynamic deployment mechanism allows the system to provide high normal force (and thus high friction) only when auxiliary wheels are deployed for straight-line movement, while retracting them during maneuvers to maintain stability. This temporal separation of functions resolves the contradiction by ensuring that high grip force is applied only when it is needed and safe to do so.
Solution Approach 2:
The system preliminarily deploys the auxiliary wheels before straight-line movement begins, ensuring they are in position to provide necessary friction. This preliminary action prevents the need to rely on low normal force during critical movement phases, resolving the slipping risk while maintaining stability during other operations.
3Ease of operation
If auxiliary wheels are deployed to control movement down long hallways, then movement control improves, but one pair of caster wheels may lift off the ground
Solution Approach 1:
The patent employs dynamic deployment of auxiliary wheels that can be activated specifically for straight-line movement down hallways. By controlling the deployment timing and force distribution, the system provides enhanced movement control along the hallway while managing the normal force distribution to prevent caster wheels from lifting off, thus resolving the contradiction between ease of operation and stability.
4Ease of operation
If auxiliary wheels are used to maneuver around corners, then directional control improves, but the auxiliary wheels may slip on the floor surface
Solution Approach 1:
The system dynamically retracts auxiliary wheels during cornering maneuvers, relying instead on the swiveling capability of the four caster wheels for directional control. This dynamic retraction prevents the auxiliary wheels from slipping during cornering while maintaining their deployment benefit for straight-line movement, resolving the contradiction between cornering control and auxiliary wheel grip.
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 enhances the stability and maneuverability of the patient transport apparatus by maintaining optimal load distribution on the auxiliary wheels, preventing teetering and slipping, and allowing for smooth navigation of various floor surfaces and obstacles.
Implementation Method 1
adjust the normal force and frictional force... preventing teetering and slipping
Data Source
AI summary
A patient transport apparatus for transporting a patient over a surface. The patient transport apparatus has support wheels coupled to a base and swivelable about swivel axes. An auxiliary wheel assembly is coupled to the base and includes an auxiliary wheel configured to move between a plurality of wheel positions, and an actuator operably coupled to the auxiliary wheel to move the auxiliary wheel between the plurality of wheel positions. A sensing system with a sensor is provided to detect a motion condition of the patient transport apparatus. A controller is coupled to the sensing system and to the actuator, and is configured to drive the actuator to move the auxiliary wheel between the plurality of wheel positions based on the motion condition of the patient transport apparatus.