Variable Force Caster Brake for Stretcher Speed Control
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Solution Overview
Problem
Conventional caster braking mechanisms on patient support apparatuses, such as stretchers, are ineffective for gradual speed control, particularly when navigating ramps or corners, as they either fully lock or fail to engage, lacking a middle ground for controlled movement.
Innovation Solution
A caster braking apparatus that engages caster wheels with a variable force, allowing for partial impeding of rotation while maintaining some mobility, utilizing a brake handle and cam mechanism to adjust the braking force, enabling controlled speed adjustments during transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional caster braking mechanisms are engaged, then the caster wheels are blocked with sufficient force to prevent any rolling, but the stretcher cannot be slowed down during transport without complete stoppage
Solution Approach 1:
The brake mechanism is designed with dynamic adjustability, allowing the brake shoe engagement force to be varied from full braking to partial braking. The cam mechanism enables continuous adjustment of the brake shoe position relative to the caster wheel, transforming a static on/off braking system into a dynamic system that can provide graduated braking forces adapted to different operational needs such as descending ramps or controlled stopping.
Solution Approach 2:
The invention changes the parameter of brake engagement force from a fixed binary state (engaged/not engaged) to a variable parameter that can be continuously adjusted. By modifying the cam mechanism geometry and its actuation, the brake shoe's contact force with the caster wheel can be varied, enabling speed control during transport while maintaining reliable stopping capability when fully engaged.
2Stability of the object's composition
If the brake engages the caster wheel with full force to prevent rolling, then the stretcher remains stationary, but gradual speed control during transport is not feasible
Solution Approach 1:
The brake mechanism is designed to allow partial engagement where the brake shoe contacts the caster wheel with insufficient force to completely prevent rolling, yet sufficient to provide resistance and enable speed control. This partial action mode allows the stretcher to move at controlled speeds during transport while still providing braking assistance, bridging the gap between complete freedom of movement and complete stationary lock.
3Ease of operation
If a foot pedal is used to control the caster braking mechanism, then the braking can be actuated, but precise control of braking force for gradual speed reduction is limited
Solution Approach 1:
A cam mechanism is introduced as an intermediary between the foot pedal actuation and the brake shoe engagement. The cam converts the foot pedal's linear or rotational motion into precise angular positioning of the brake shoe relative to the caster wheel. This intermediary mechanism provides mechanical advantage and precise control, allowing the operator to modulate braking force smoothly from zero to full engagement through controlled foot pressure and pedal position.
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
Enables caregivers to slow the stretcher's movement without complete stoppage, improving safety and efficiency, especially when transporting obese patients or navigating ramps, potentially reducing the number of caregivers required.
Implementation Method 1
utilizing a brake handle and cam mechanism to adjust the braking force
Implementation Method 2
the brake engages the associated caster wheel with a second force that is less than the first force
Data Source
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AI summary
A patient support apparatus (20) includes a frame (22, 26), a plurality of casters (24) coupled to the frame (22), and a push handle (68) that is coupled to the frame (26) and that is gripable to maneuver the patient support apparatus (20) along a floor (50). The patient support apparatus (20) also has a brake handle (302) that is coupled to the push handle (68) and that is movable to brake at least one of the casters (24).